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| Started by | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| First post | 2016-08-09 22:40 +0200 |
| Last post | 2016-08-09 22:40 +0200 |
| Articles | 12 — 2 participants |
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[PATCH v14 00/14] support "task_isolation" mode Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
[PATCH v14 06/14] arch/x86: enable task isolation functionality Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
Re: [PATCH v14 06/14] arch/x86: enable task isolation functionality Andy Lutomirski <luto@amacapital.net> - 2016-08-10 21:20 +0200
Re: [PATCH v14 06/14] arch/x86: enable task isolation functionality Andy Lutomirski <luto@amacapital.net> - 2016-08-10 22:10 +0200
Re: [PATCH v14 06/14] arch/x86: enable task isolation functionality Andy Lutomirski <luto@amacapital.net> - 2016-08-10 21:20 +0200
[PATCH v14 10/14] arm, tile: turn off timer tick for oneshot_stopped state Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
[PATCH v14 02/14] vmstat: add vmstat_idle function Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
[PATCH v14 08/14] arch/arm64: enable task isolation functionality Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
[PATCH v14 05/14] task_isolation: track asynchronous interrupts Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
[PATCH v14 09/14] arch/tile: enable task isolation functionality Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
[PATCH v14 04/14] task_isolation: add initial support Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
[PATCH v14 07/14] arm64: factor work_pending state machine to C Chris Metcalf <cmetcalf@mellanox.com> - 2016-08-09 22:40 +0200
| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 00/14] support "task_isolation" mode |
| Message-ID | <s4lYB-3WM-3@gated-at.bofh.it> |
Here is a respin of the task-isolation patch set. This primarily reflects some testing on x86, and a rebase to 4.8. I have been getting email asking me when and where this patch will be upstreamed so folks can start using it. I had been thinking the obvious path was via Frederic Weisbecker to Ingo as a NOHZ kind of thing. But perhaps it touches enough other subsystems that that doesn't really make sense? Andrew, would it make sense to take it directly via your tree? Frederic, Ingo, what do you think? Changes since v13: - Rebased on v4.8-rc1 (and thus uses the standard try_get_task_struct). - Fixes a bug when using the clocksource watchdog; it is now scheduled to run only on the housekeeping cpus [by Christoph Lameter]. - Fixes a bug in x86 syscall_trace_enter() [seen by Francis Giraldeau]. - Includes a selftest. The previous (v13) patch series is here: https://lkml.kernel.org/r/1468529299-27929-1-git-send-email-cmetcalf@mellanox.com This version of the patch series has been tested on arm64 and tilegx, and build-tested on x86 (plus some volunteer testing on x86 by Christoph and Francis). It remains true that the 1 Hz tick needs to be disabled for this patch series to be able to achieve its primary goal of enabling truly tick-free operation, but that is ongoing orthogonal work. Frederic, do you have a sense of what is left to be done there? I can certainly try to contribute to that effort as well. The series is available at: git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile.git dataplane Chris Metcalf (13): vmstat: add quiet_vmstat_sync function vmstat: add vmstat_idle function lru_add_drain_all: factor out lru_add_drain_needed task_isolation: add initial support task_isolation: track asynchronous interrupts arch/x86: enable task isolation functionality arm64: factor work_pending state machine to C arch/arm64: enable task isolation functionality arch/tile: enable task isolation functionality arm, tile: turn off timer tick for oneshot_stopped state task_isolation: support CONFIG_TASK_ISOLATION_ALL task_isolation: add user-settable notification signal task_isolation self test Christoph Lameter (1): clocksource: Do not schedule watchdog on isolated or NOHZ cpus Documentation/kernel-parameters.txt | 16 + arch/arm64/Kconfig | 1 + arch/arm64/include/asm/thread_info.h | 5 +- arch/arm64/kernel/entry.S | 12 +- arch/arm64/kernel/ptrace.c | 15 +- arch/arm64/kernel/signal.c | 42 +- arch/arm64/kernel/smp.c | 2 + arch/arm64/mm/fault.c | 8 +- arch/tile/Kconfig | 1 + arch/tile/include/asm/thread_info.h | 4 +- arch/tile/kernel/process.c | 9 + arch/tile/kernel/ptrace.c | 7 + arch/tile/kernel/single_step.c | 7 + arch/tile/kernel/smp.c | 26 +- arch/tile/kernel/time.c | 1 + arch/tile/kernel/unaligned.c | 4 + arch/tile/mm/fault.c | 13 +- arch/tile/mm/homecache.c | 2 + arch/x86/Kconfig | 1 + arch/x86/entry/common.c | 20 +- arch/x86/include/asm/thread_info.h | 2 + arch/x86/kernel/smp.c | 2 + arch/x86/kernel/traps.c | 3 + arch/x86/mm/fault.c | 5 + drivers/base/cpu.c | 18 + drivers/clocksource/arm_arch_timer.c | 2 + include/linux/context_tracking_state.h | 6 + include/linux/isolation.h | 73 +++ include/linux/sched.h | 3 + include/linux/swap.h | 1 + include/linux/tick.h | 2 + include/linux/vmstat.h | 4 + include/uapi/linux/prctl.h | 10 + init/Kconfig | 37 ++ kernel/Makefile | 1 + kernel/fork.c | 3 + kernel/irq_work.c | 5 +- kernel/isolation.c | 337 +++++++++++ kernel/sched/core.c | 14 + kernel/signal.c | 15 + kernel/smp.c | 6 +- kernel/softirq.c | 33 ++ kernel/sys.c | 9 + kernel/time/clocksource.c | 10 +- kernel/time/tick-sched.c | 36 +- mm/swap.c | 15 +- mm/vmstat.c | 19 + tools/testing/selftests/Makefile | 1 + tools/testing/selftests/task_isolation/Makefile | 11 + tools/testing/selftests/task_isolation/config | 2 + tools/testing/selftests/task_isolation/isolation.c | 618 +++++++++++++++++++++ 51 files changed, 1440 insertions(+), 59 deletions(-) create mode 100644 include/linux/isolation.h create mode 100644 kernel/isolation.c create mode 100644 tools/testing/selftests/task_isolation/Makefile create mode 100644 tools/testing/selftests/task_isolation/config create mode 100644 tools/testing/selftests/task_isolation/isolation.c -- 2.7.2
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| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 06/14] arch/x86: enable task isolation functionality |
| Message-ID | <s4lYC-3WM-19@gated-at.bofh.it> |
| In reply to | #1459107 |
In exit_to_usermode_loop(), call task_isolation_ready() for
TIF_TASK_ISOLATION tasks when we are checking the thread-info flags,
and after we've handled the other work, call task_isolation_enter()
for such tasks.
In syscall_trace_enter_phase1(), we add the necessary support for
reporting syscalls for task-isolation processes.
We add strict reporting for the kernel exception types that do
not result in signals, namely non-signalling page faults and
non-signalling MPX fixups.
Tested-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
arch/x86/Kconfig | 1 +
arch/x86/entry/common.c | 20 +++++++++++++++++++-
arch/x86/include/asm/thread_info.h | 2 ++
arch/x86/kernel/smp.c | 2 ++
arch/x86/kernel/traps.c | 3 +++
arch/x86/mm/fault.c | 5 +++++
6 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5c6e7471b732..10b2c0567dad 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -89,6 +89,7 @@ config X86
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_SOFT_DIRTY if X86_64
+ select HAVE_ARCH_TASK_ISOLATION
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_EBPF_JIT if X86_64
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 1433f6b4607d..5c1b9fc89bf2 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -21,6 +21,7 @@
#include <linux/context_tracking.h>
#include <linux/user-return-notifier.h>
#include <linux/uprobes.h>
+#include <linux/isolation.h>
#include <asm/desc.h>
#include <asm/traps.h>
@@ -91,6 +92,15 @@ static long syscall_trace_enter(struct pt_regs *regs)
if (emulated)
return -1L;
+ /* In isolation mode, we may prevent the syscall from running. */
+ if (work & _TIF_TASK_ISOLATION) {
+ if (task_isolation_syscall(regs->orig_ax) == -1) {
+ regs->orig_ax = -1;
+ return 0;
+ }
+ work &= ~_TIF_TASK_ISOLATION;
+ }
+
#ifdef CONFIG_SECCOMP
/*
* Do seccomp after ptrace, to catch any tracer changes.
@@ -136,7 +146,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
#define EXIT_TO_USERMODE_LOOP_FLAGS \
(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
- _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)
+ _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY | _TIF_TASK_ISOLATION)
static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
{
@@ -170,11 +180,19 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
if (cached_flags & _TIF_USER_RETURN_NOTIFY)
fire_user_return_notifiers();
+ if (cached_flags & _TIF_TASK_ISOLATION)
+ task_isolation_enter();
+
/* Disable IRQs and retry */
local_irq_disable();
cached_flags = READ_ONCE(pt_regs_to_thread_info(regs)->flags);
+ /* Clear task isolation from cached_flags manually. */
+ if ((cached_flags & _TIF_TASK_ISOLATION) &&
+ task_isolation_ready())
+ cached_flags &= ~_TIF_TASK_ISOLATION;
+
if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
break;
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 84b59846154a..eb3b648617c1 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -93,6 +93,7 @@ struct thread_info {
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */
#define TIF_UPROBE 12 /* breakpointed or singlestepping */
+#define TIF_TASK_ISOLATION 13 /* task isolation enabled for task */
#define TIF_NOTSC 16 /* TSC is not accessible in userland */
#define TIF_IA32 17 /* IA32 compatibility process */
#define TIF_FORK 18 /* ret_from_fork */
@@ -117,6 +118,7 @@ struct thread_info {
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
#define _TIF_UPROBE (1 << TIF_UPROBE)
+#define _TIF_TASK_ISOLATION (1 << TIF_TASK_ISOLATION)
#define _TIF_NOTSC (1 << TIF_NOTSC)
#define _TIF_IA32 (1 << TIF_IA32)
#define _TIF_FORK (1 << TIF_FORK)
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 658777cf3851..e4ffd9581cdb 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -23,6 +23,7 @@
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/gfp.h>
+#include <linux/isolation.h>
#include <asm/mtrr.h>
#include <asm/tlbflush.h>
@@ -125,6 +126,7 @@ static void native_smp_send_reschedule(int cpu)
WARN_ON(1);
return;
}
+ task_isolation_debug(cpu, "reschedule IPI");
apic->send_IPI(cpu, RESCHEDULE_VECTOR);
}
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index b70ca12dd389..eae51685c2b3 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -36,6 +36,7 @@
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/io.h>
+#include <linux/isolation.h>
#ifdef CONFIG_EISA
#include <linux/ioport.h>
@@ -383,6 +384,8 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
case 2: /* Bound directory has invalid entry. */
if (mpx_handle_bd_fault())
goto exit_trap;
+ /* No signal was generated, but notify task-isolation tasks. */
+ task_isolation_quiet_exception("bounds check");
break; /* Success, it was handled */
case 1: /* Bound violation. */
info = mpx_generate_siginfo(regs);
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index dc8023060456..b1509876794c 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -14,6 +14,7 @@
#include <linux/prefetch.h> /* prefetchw */
#include <linux/context_tracking.h> /* exception_enter(), ... */
#include <linux/uaccess.h> /* faulthandler_disabled() */
+#include <linux/isolation.h> /* task_isolation_quiet_exception */
#include <asm/cpufeature.h> /* boot_cpu_has, ... */
#include <asm/traps.h> /* dotraplinkage, ... */
@@ -1397,6 +1398,10 @@ good_area:
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
}
+ /* No signal was generated, but notify task-isolation tasks. */
+ if (flags & PF_USER)
+ task_isolation_quiet_exception("page fault at %#lx", address);
+
check_v8086_mode(regs, address, tsk);
}
NOKPROBE_SYMBOL(__do_page_fault);
--
2.7.2
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2016-08-10 21:20 +0200 |
| Subject | Re: [PATCH v14 06/14] arch/x86: enable task isolation functionality |
| Message-ID | <s4HcK-NR-33@gated-at.bofh.it> |
| In reply to | #1459108 |
On Aug 10, 2016 5:30 PM, "Chris Metcalf" <cmetcalf@mellanox.com> wrote:
>
> On 8/10/2016 3:52 AM, Andy Lutomirski wrote:
>>
>> On Aug 9, 2016 11:30 PM, "Chris Metcalf" <cmetcalf@mellanox.com> wrote:
>> @@ -91,6 +92,15 @@ static long syscall_trace_enter(struct pt_regs *regs)
>> if (emulated)
>> return -1L;
>>
>> + /* In isolation mode, we may prevent the syscall from running. */
>> + if (work & _TIF_TASK_ISOLATION) {
>> + if (task_isolation_syscall(regs->orig_ax) == -1) {
>> + regs->orig_ax = -1;
>> + return 0;
>> + }
>> + work &= ~_TIF_TASK_ISOLATION;
>> + }
>> +
>> What is this? It's not mentioned in the changelog. It seems
>> nonsensical to me. If nothing else, you forgot to update regs->ax,
>> but I don't even know what you're trying to do.
>
>
> It's mentioned in the changelog as "Fixes a bug in x86 syscall_trace_enter()
> [seen by Francis Giraldeau]." To be fair, I didn't hear back from Francis, and
> you're right, this doesn't look like it makes any sense now. (I've added him
> to the cc's on this email; for this series I had just put him on the cover letter.)
>
> I modeled this code on a snippet from the old two-phase syscall entry work:
>
> if (ret == SECCOMP_PHASE1_SKIP) {
> regs->orig_ax = -1;
> ret = 0;
> }
>
> You got rid of this during the 4.7-rc series, but my code above was at least
> plausibly valid until then :-)
>
> Regardless, I assume that the right thing for that condition to do now when
> it triggers is to set regs->ax = -ENOSYS and return -1L? I'll update the
> git repository with that in any case.
regs->ax will already be -ENOSYS unless something changed it, but I'm
not sure what this code is trying to do. Is the idea that
task_isolation_syscall might enqueue a signal and you want to deliver
it without processing the syscall? If so, a comment would be nice.
You could even WARN_ON(!signal_pending()).
>
> Thanks!
>
>
>>> #ifdef CONFIG_SECCOMP
>>> /*
>>> * Do seccomp after ptrace, to catch any tracer changes.
>>> @@ -136,7 +146,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
>>>
>>> #define EXIT_TO_USERMODE_LOOP_FLAGS \
>>> (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
>>> - _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)
>>> + _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY | _TIF_TASK_ISOLATION)
>>>
>> Where are you updating the conditions to force use of the slow path?
>> (That's _TIF_ALLWORK_MASK.)
>
>
> Whenever _TIF_TASK_ISOLATION is set, _TIF_NOHZ is also set.
OK, but why not decouple it a bit and add it to the mask? I keep
meaning to add a BUILD_BUG_ON checking for bits in
EXIT_TO_USERMODE_LOOP_FLAGS that aren't in the appropriate slow path
masks.
>
> --
> Chris Metcalf, Mellanox Technologies
> http://www.mellanox.com
>
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2016-08-10 22:10 +0200 |
| Subject | Re: [PATCH v14 06/14] arch/x86: enable task isolation functionality |
| Message-ID | <s4HZ8-1pa-35@gated-at.bofh.it> |
| In reply to | #1459628 |
On Wed, Aug 10, 2016 at 12:40 PM, Chris Metcalf <cmetcalf@mellanox.com> wrote:
> On 8/10/2016 3:17 PM, Andy Lutomirski wrote:
>>
>> On Aug 10, 2016 5:30 PM, "Chris Metcalf" <cmetcalf@mellanox.com> wrote:
>>>
>>> On 8/10/2016 3:52 AM, Andy Lutomirski wrote:
>>>>
>>>> On Aug 9, 2016 11:30 PM, "Chris Metcalf" <cmetcalf@mellanox.com> wrote:
>>>> @@ -91,6 +92,15 @@ static long syscall_trace_enter(struct pt_regs *regs)
>>>> if (emulated)
>>>> return -1L;
>>>>
>>>> + /* In isolation mode, we may prevent the syscall from running.
>>>> */
>>>> + if (work & _TIF_TASK_ISOLATION) {
>>>> + if (task_isolation_syscall(regs->orig_ax) == -1) {
>>>> + regs->orig_ax = -1;
>>>> + return 0;
>>>> + }
>>>> + work &= ~_TIF_TASK_ISOLATION;
>>>> + }
>>>> +
>>>> What is this? It's not mentioned in the changelog. It seems
>>>> nonsensical to me. If nothing else, you forgot to update regs->ax,
>>>> but I don't even know what you're trying to do.
>>>
>>>
>>> It's mentioned in the changelog as "Fixes a bug in x86
>>> syscall_trace_enter()
>>> [seen by Francis Giraldeau]." To be fair, I didn't hear back from
>>> Francis, and
>>> you're right, this doesn't look like it makes any sense now. (I've added
>>> him
>>> to the cc's on this email; for this series I had just put him on the
>>> cover letter.)
>>>
>>> I modeled this code on a snippet from the old two-phase syscall entry
>>> work:
>>>
>>> if (ret == SECCOMP_PHASE1_SKIP) {
>>> regs->orig_ax = -1;
>>> ret = 0;
>>> }
>>>
>>> You got rid of this during the 4.7-rc series, but my code above was at
>>> least
>>> plausibly valid until then :-)
>>>
>>> Regardless, I assume that the right thing for that condition to do now
>>> when
>>> it triggers is to set regs->ax = -ENOSYS and return -1L? I'll update the
>>> git repository with that in any case.
>>
>> regs->ax will already be -ENOSYS unless something changed it
>
>
> Right, I see that now in entry_SYSCALL_64_after_swapgs. Good.
>
>> but I'm
>> not sure what this code is trying to do. Is the idea that
>> task_isolation_syscall might enqueue a signal and you want to deliver
>> it without processing the syscall? If so, a comment would be nice.
>> You could even WARN_ON(!signal_pending()).
>
>
> If you are in task isolation mode (and you haven't also requested NOSIG),
> then attempting a system call fails, and you get a signal delivered. You
> convinced me that failing the syscall was the thing to do back here:
>
> https://lkml.kernel.org/r/CALCETrUrc_LJyLJLHefSDYagCrNqqzKuknr6uLgVXnPW8PmZKw@mail.gmail.com
Indeed. Then please add the comment any maybe the WARN_ON.
>
>>>>> #ifdef CONFIG_SECCOMP
>>>>> /*
>>>>> * Do seccomp after ptrace, to catch any tracer changes.
>>>>> @@ -136,7 +146,7 @@ static long syscall_trace_enter(struct pt_regs
>>>>> *regs)
>>>>>
>>>>> #define EXIT_TO_USERMODE_LOOP_FLAGS \
>>>>> (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
>>>>> - _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)
>>>>> + _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY |
>>>>> _TIF_TASK_ISOLATION)
>>>>>
>>>> Where are you updating the conditions to force use of the slow path?
>>>> (That's _TIF_ALLWORK_MASK.)
>>>
>>>
>>> Whenever _TIF_TASK_ISOLATION is set, _TIF_NOHZ is also set.
>>
>> OK, but why not decouple it a bit and add it to the mask? I keep
>> meaning to add a BUILD_BUG_ON checking for bits in
>> EXIT_TO_USERMODE_LOOP_FLAGS that aren't in the appropriate slow path
>> masks.
>
>
> That does seem reasonable; I'll make the change.
>
>
> --
> Chris Metcalf, Mellanox Technologies
> http://www.mellanox.com
>
--
Andy Lutomirski
AMA Capital Management, LLC
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2016-08-10 21:20 +0200 |
| Subject | Re: [PATCH v14 06/14] arch/x86: enable task isolation functionality |
| Message-ID | <s4HcK-NR-35@gated-at.bofh.it> |
| In reply to | #1459108 |
On Aug 9, 2016 11:30 PM, "Chris Metcalf" <cmetcalf@mellanox.com> wrote:
>
> In exit_to_usermode_loop(), call task_isolation_ready() for
> TIF_TASK_ISOLATION tasks when we are checking the thread-info flags,
> and after we've handled the other work, call task_isolation_enter()
> for such tasks.
>
> In syscall_trace_enter_phase1(), we add the necessary support for
> reporting syscalls for task-isolation processes.
>
> We add strict reporting for the kernel exception types that do
> not result in signals, namely non-signalling page faults and
> non-signalling MPX fixups.
>
> Tested-by: Christoph Lameter <cl@linux.com>
> Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/entry/common.c | 20 +++++++++++++++++++-
> arch/x86/include/asm/thread_info.h | 2 ++
> arch/x86/kernel/smp.c | 2 ++
> arch/x86/kernel/traps.c | 3 +++
> arch/x86/mm/fault.c | 5 +++++
> 6 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 5c6e7471b732..10b2c0567dad 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -89,6 +89,7 @@ config X86
> select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
> select HAVE_ARCH_SECCOMP_FILTER
> select HAVE_ARCH_SOFT_DIRTY if X86_64
> + select HAVE_ARCH_TASK_ISOLATION
> select HAVE_ARCH_TRACEHOOK
> select HAVE_ARCH_TRANSPARENT_HUGEPAGE
> select HAVE_EBPF_JIT if X86_64
> diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
> index 1433f6b4607d..5c1b9fc89bf2 100644
> --- a/arch/x86/entry/common.c
> +++ b/arch/x86/entry/common.c
> @@ -21,6 +21,7 @@
> #include <linux/context_tracking.h>
> #include <linux/user-return-notifier.h>
> #include <linux/uprobes.h>
> +#include <linux/isolation.h>
>
> #include <asm/desc.h>
> #include <asm/traps.h>
> @@ -91,6 +92,15 @@ static long syscall_trace_enter(struct pt_regs *regs)
> if (emulated)
> return -1L;
>
> + /* In isolation mode, we may prevent the syscall from running. */
> + if (work & _TIF_TASK_ISOLATION) {
> + if (task_isolation_syscall(regs->orig_ax) == -1) {
> + regs->orig_ax = -1;
> + return 0;
> + }
> + work &= ~_TIF_TASK_ISOLATION;
> + }
> +
What is this? It's not mentioned in the changelog. It seems
nonsensical to me. If nothing else, you forgot to update regs->ax,
but I don't even know what you're trying to do.
> #ifdef CONFIG_SECCOMP
> /*
> * Do seccomp after ptrace, to catch any tracer changes.
> @@ -136,7 +146,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
>
> #define EXIT_TO_USERMODE_LOOP_FLAGS \
> (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
> - _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY)
> + _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY | _TIF_TASK_ISOLATION)
>
Where are you updating the conditions to force use of the slow path?
(That's _TIF_ALLWORK_MASK.)
--Andy
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| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 10/14] arm, tile: turn off timer tick for oneshot_stopped state |
| Message-ID | <s4lYC-3WM-23@gated-at.bofh.it> |
| In reply to | #1459107 |
When the schedule tick is disabled in tick_nohz_stop_sched_tick(),
we call hrtimer_cancel(), which eventually calls down into
__remove_hrtimer() and thus into hrtimer_force_reprogram().
That function's call to tick_program_event() detects that
we are trying to set the expiration to KTIME_MAX and calls
clockevents_switch_state() to set the state to ONESHOT_STOPPED,
and returns. See commit 8fff52fd5093 ("clockevents: Introduce
CLOCK_EVT_STATE_ONESHOT_STOPPED state") for more background.
However, by default the internal __clockevents_switch_state() code
doesn't have a "set_state_oneshot_stopped" function pointer for
the arm_arch_timer or tile clock_event_device structures, so that
code returns -ENOSYS, and we end up not setting the state, and more
importantly, we don't actually turn off the hardware timer.
As a result, the timer tick we were waiting for before is still
queued, and fires shortly afterwards, only to discover there was
nothing for it to do, at which point it quiesces.
The fix is to provide that function pointer field, and like the
other function pointers, have it just turn off the timer interrupt.
Any call to set a new timer interval will properly re-enable it.
This fix avoids a small performance hiccup for regular applications,
but for TASK_ISOLATION code, it fixes a potentially serious
kernel timer interruption to the time-sensitive application.
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
arch/tile/kernel/time.c | 1 +
drivers/clocksource/arm_arch_timer.c | 2 ++
2 files changed, 3 insertions(+)
diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c
index 178989e6d3e3..fbedf380d9d4 100644
--- a/arch/tile/kernel/time.c
+++ b/arch/tile/kernel/time.c
@@ -159,6 +159,7 @@ static DEFINE_PER_CPU(struct clock_event_device, tile_timer) = {
.set_next_event = tile_timer_set_next_event,
.set_state_shutdown = tile_timer_shutdown,
.set_state_oneshot = tile_timer_shutdown,
+ .set_state_oneshot_stopped = tile_timer_shutdown,
.tick_resume = tile_timer_shutdown,
};
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 28bce3f4f81d..c725156e5a21 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -314,6 +314,8 @@ static void __arch_timer_setup(unsigned type,
}
}
+ clk->set_state_oneshot_stopped = clk->set_state_shutdown;
+
clk->set_state_shutdown(clk);
clockevents_config_and_register(clk, arch_timer_rate, 0xf, 0x7fffffff);
--
2.7.2
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| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 02/14] vmstat: add vmstat_idle function |
| Message-ID | <s4lYC-3WM-25@gated-at.bofh.it> |
| In reply to | #1459107 |
This function checks to see if a vmstat worker is not running,
and the vmstat diffs don't require an update. The function is
called from the task-isolation code to see if we need to
actually do some work to quiet vmstat.
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
include/linux/vmstat.h | 2 ++
mm/vmstat.c | 10 ++++++++++
2 files changed, 12 insertions(+)
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index fab62aa74079..69b6cc4be909 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -235,6 +235,7 @@ extern void __dec_node_state(struct pglist_data *, enum node_stat_item);
void quiet_vmstat(void);
void quiet_vmstat_sync(void);
+bool vmstat_idle(void);
void cpu_vm_stats_fold(int cpu);
void refresh_zone_stat_thresholds(void);
@@ -338,6 +339,7 @@ static inline void refresh_zone_stat_thresholds(void) { }
static inline void cpu_vm_stats_fold(int cpu) { }
static inline void quiet_vmstat(void) { }
static inline void quiet_vmstat_sync(void) { }
+static inline bool vmstat_idle(void) { return true; }
static inline void drain_zonestat(struct zone *zone,
struct per_cpu_pageset *pset) { }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 57fc29750da6..7dd17c06d3a7 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1763,6 +1763,16 @@ void quiet_vmstat_sync(void)
}
/*
+ * Report on whether vmstat processing is quiesced on the core currently:
+ * no vmstat worker running and no vmstat updates to perform.
+ */
+bool vmstat_idle(void)
+{
+ return !delayed_work_pending(this_cpu_ptr(&vmstat_work)) &&
+ !need_update(smp_processor_id());
+}
+
+/*
* Shepherd worker thread that checks the
* differentials of processors that have their worker
* threads for vm statistics updates disabled because of
--
2.7.2
[toc] | [prev] | [next] | [standalone]
| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 08/14] arch/arm64: enable task isolation functionality |
| Message-ID | <s4lYC-3WM-31@gated-at.bofh.it> |
| In reply to | #1459107 |
In do_notify_resume(), call task_isolation_ready() for
TIF_TASK_ISOLATION tasks when we are checking the thread-info flags;
and after we've handled the other work, call task_isolation_enter()
for such tasks. To ensure we always call task_isolation_enter() when
returning to userspace, add _TIF_TASK_ISOLATION to _TIF_WORK_MASK,
while leaving the old bitmask value as _TIF_WORK_LOOP_MASK to
check while looping.
We tweak syscall_trace_enter() slightly to carry the "flags"
value from current_thread_info()->flags for each of the tests,
rather than doing a volatile read from memory for each one. This
avoids a small overhead for each test, and in particular avoids
that overhead for TIF_NOHZ when TASK_ISOLATION is not enabled.
We instrument the smp_send_reschedule() routine so that it checks for
isolated tasks and generates a suitable warning if we are about
to disturb one of them in strict or debug mode.
Finally, report on page faults in task-isolation processes in
do_page_faults().
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/thread_info.h | 5 ++++-
arch/arm64/kernel/ptrace.c | 15 ++++++++++++---
arch/arm64/kernel/signal.c | 10 ++++++++++
arch/arm64/kernel/smp.c | 2 ++
arch/arm64/mm/fault.c | 8 +++++++-
6 files changed, 36 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 69c8787bec7d..1aea9a329b85 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -61,6 +61,7 @@ config ARM64
select HAVE_ARCH_MMAP_RND_BITS
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
select HAVE_ARCH_SECCOMP_FILTER
+ select HAVE_ARCH_TASK_ISOLATION
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_ARM_SMCCC
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index abd64bd1f6d9..bdc6426b9968 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -109,6 +109,7 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_NEED_RESCHED 1
#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
+#define TIF_TASK_ISOLATION 4
#define TIF_NOHZ 7
#define TIF_SYSCALL_TRACE 8
#define TIF_SYSCALL_AUDIT 9
@@ -124,6 +125,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
+#define _TIF_TASK_ISOLATION (1 << TIF_TASK_ISOLATION)
#define _TIF_NOHZ (1 << TIF_NOHZ)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
@@ -132,7 +134,8 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_32BIT (1 << TIF_32BIT)
#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
- _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE)
+ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
+ _TIF_TASK_ISOLATION)
#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index e0c81da60f76..9b25ffb436cc 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -37,6 +37,7 @@
#include <linux/regset.h>
#include <linux/tracehook.h>
#include <linux/elf.h>
+#include <linux/isolation.h>
#include <asm/compat.h>
#include <asm/debug-monitors.h>
@@ -1347,14 +1348,22 @@ static void tracehook_report_syscall(struct pt_regs *regs,
asmlinkage int syscall_trace_enter(struct pt_regs *regs)
{
- if (test_thread_flag(TIF_SYSCALL_TRACE))
+ unsigned long work = ACCESS_ONCE(current_thread_info()->flags);
+
+ if (work & _TIF_SYSCALL_TRACE)
tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
- /* Do the secure computing after ptrace; failures should be fast. */
+ /* In isolation mode, we may prevent the syscall from running. */
+ if (work & _TIF_TASK_ISOLATION) {
+ if (task_isolation_syscall(regs->syscallno) == -1)
+ return -1;
+ }
+
+ /* Do the secure computing check early; failures should be fast. */
if (secure_computing(NULL) == -1)
return -1;
- if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
+ if (work & _TIF_SYSCALL_TRACEPOINT)
trace_sys_enter(regs, regs->syscallno);
audit_syscall_entry(regs->syscallno, regs->orig_x0, regs->regs[1],
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 404dd67080b9..f9b9b25636ca 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -25,6 +25,7 @@
#include <linux/uaccess.h>
#include <linux/tracehook.h>
#include <linux/ratelimit.h>
+#include <linux/isolation.h>
#include <asm/debug-monitors.h>
#include <asm/elf.h>
@@ -424,9 +425,18 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
if (thread_flags & _TIF_FOREIGN_FPSTATE)
fpsimd_restore_current_state();
+
+ if (thread_flags & _TIF_TASK_ISOLATION)
+ task_isolation_enter();
}
local_irq_disable();
thread_flags = READ_ONCE(current_thread_info()->flags);
+
+ /* Clear task isolation from cached_flags manually. */
+ if ((thread_flags & _TIF_TASK_ISOLATION) &&
+ task_isolation_ready())
+ thread_flags &= ~_TIF_TASK_ISOLATION;
+
} while (thread_flags & _TIF_WORK_MASK);
}
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 76a6d9263908..ed75244014f5 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -37,6 +37,7 @@
#include <linux/completion.h>
#include <linux/of.h>
#include <linux/irq_work.h>
+#include <linux/isolation.h>
#include <asm/alternative.h>
#include <asm/atomic.h>
@@ -874,6 +875,7 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
void smp_send_reschedule(int cpu)
{
+ task_isolation_debug(cpu, "reschedule IPI");
smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
}
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index c8beaa0da7df..f0c4d6ba346e 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -29,6 +29,7 @@
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/perf_event.h>
+#include <linux/isolation.h>
#include <asm/cpufeature.h>
#include <asm/exception.h>
@@ -382,8 +383,13 @@ retry:
* Handle the "normal" case first - VM_FAULT_MAJOR
*/
if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP |
- VM_FAULT_BADACCESS))))
+ VM_FAULT_BADACCESS)))) {
+ /* No signal was generated, but notify task-isolation tasks. */
+ if (user_mode(regs))
+ task_isolation_quiet_exception("page fault at %#lx",
+ addr);
return 0;
+ }
/*
* If we are in kernel mode at this point, we have no context to
--
2.7.2
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| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 05/14] task_isolation: track asynchronous interrupts |
| Message-ID | <s4lYC-3WM-21@gated-at.bofh.it> |
| In reply to | #1459107 |
This commit adds support for tracking asynchronous interrupts
delivered to task-isolation tasks, e.g. IPIs or IRQs. Just
as for exceptions and syscalls, when this occurs we arrange to
deliver a signal to the task so that it knows it has been
interrupted. If the task is interrupted by an NMI, we can't
safely deliver a signal, so we just dump out a console stack.
We also support a new "task_isolation_debug" flag which forces
the console stack to be dumped out regardless. We try to catch
the original source of the interrupt, e.g. if an IPI is dispatched
to a task-isolation task, we dump the backtrace of the remote
core that is sending the IPI, rather than just dumping out a
trace showing the core received an IPI from somewhere.
Calls to task_isolation_debug() can be placed in the
platform-independent code when that results in fewer lines
of code changes, as for example is true of the users of the
arch_send_call_function_*() APIs. Or, they can be placed in the
per-architecture code when there are many callers, as for example
is true of the smp_send_reschedule() call.
A further cleanup might be to create an intermediate layer, so that
for example smp_send_reschedule() is a single generic function that
just calls arch_smp_send_reschedule(), allowing generic code to be
called every time smp_send_reschedule() is invoked. But for now,
we just update either callers or callees as makes most sense.
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
Documentation/kernel-parameters.txt | 8 ++++
include/linux/context_tracking_state.h | 6 +++
include/linux/isolation.h | 13 ++++++
kernel/irq_work.c | 5 ++-
kernel/isolation.c | 74 ++++++++++++++++++++++++++++++++++
kernel/sched/core.c | 14 +++++++
kernel/signal.c | 7 ++++
kernel/smp.c | 6 ++-
kernel/softirq.c | 33 +++++++++++++++
9 files changed, 164 insertions(+), 2 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7f1336b50dcc..f172cd310cf4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3951,6 +3951,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
also sets up nohz_full and isolcpus mode for the
listed set of cpus.
+ task_isolation_debug [KNL]
+ In kernels built with CONFIG_TASK_ISOLATION
+ and booted in task_isolation= mode, this
+ setting will generate console backtraces when
+ the kernel is about to interrupt a task that
+ has requested PR_TASK_ISOLATION_ENABLE and is
+ running on a task_isolation core.
+
tcpmhash_entries= [KNL,NET]
Set the number of tcp_metrics_hash slots.
Default value is 8192 or 16384 depending on total
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 1d34fe68f48a..4e2c4b900b82 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -39,8 +39,14 @@ static inline bool context_tracking_in_user(void)
{
return __this_cpu_read(context_tracking.state) == CONTEXT_USER;
}
+
+static inline bool context_tracking_cpu_in_user(int cpu)
+{
+ return per_cpu(context_tracking.state, cpu) == CONTEXT_USER;
+}
#else
static inline bool context_tracking_in_user(void) { return false; }
+static inline bool context_tracking_cpu_in_user(int cpu) { return false; }
static inline bool context_tracking_active(void) { return false; }
static inline bool context_tracking_is_enabled(void) { return false; }
static inline bool context_tracking_cpu_is_enabled(void) { return false; }
diff --git a/include/linux/isolation.h b/include/linux/isolation.h
index d9288b85b41f..02728b1f8775 100644
--- a/include/linux/isolation.h
+++ b/include/linux/isolation.h
@@ -46,6 +46,17 @@ extern void _task_isolation_quiet_exception(const char *fmt, ...);
_task_isolation_quiet_exception(fmt, ## __VA_ARGS__); \
} while (0)
+extern void _task_isolation_debug(int cpu, const char *type);
+#define task_isolation_debug(cpu, type) \
+ do { \
+ if (task_isolation_possible(cpu)) \
+ _task_isolation_debug(cpu, type); \
+ } while (0)
+
+extern void task_isolation_debug_cpumask(const struct cpumask *,
+ const char *type);
+extern void task_isolation_debug_task(int cpu, struct task_struct *p,
+ const char *type);
#else
static inline void task_isolation_init(void) { }
static inline bool task_isolation_possible(int cpu) { return false; }
@@ -55,6 +66,8 @@ extern inline void task_isolation_set_flags(struct task_struct *p,
unsigned int flags) { }
static inline int task_isolation_syscall(int nr) { return 0; }
static inline void task_isolation_quiet_exception(const char *fmt, ...) { }
+static inline void task_isolation_debug(int cpu, const char *type) { }
+#define task_isolation_debug_cpumask(mask, type) do {} while (0)
#endif
#endif
diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index bcf107ce0854..15f3d44acf11 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -17,6 +17,7 @@
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/smp.h>
+#include <linux/isolation.h>
#include <asm/processor.h>
@@ -75,8 +76,10 @@ bool irq_work_queue_on(struct irq_work *work, int cpu)
if (!irq_work_claim(work))
return false;
- if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
+ if (llist_add(&work->llnode, &per_cpu(raised_list, cpu))) {
+ task_isolation_debug(cpu, "irq_work");
arch_send_call_function_single_ipi(cpu);
+ }
return true;
}
diff --git a/kernel/isolation.c b/kernel/isolation.c
index bf3ebb0a727c..7cd57ca95be5 100644
--- a/kernel/isolation.c
+++ b/kernel/isolation.c
@@ -11,6 +11,7 @@
#include <linux/vmstat.h>
#include <linux/isolation.h>
#include <linux/syscalls.h>
+#include <linux/ratelimit.h>
#include <asm/unistd.h>
#include <asm/syscall.h>
#include "time/tick-sched.h"
@@ -215,3 +216,76 @@ int task_isolation_syscall(int syscall)
-ERESTARTNOINTR, -1);
return -1;
}
+
+/* Enable debugging of any interrupts of task_isolation cores. */
+static int task_isolation_debug_flag;
+static int __init task_isolation_debug_func(char *str)
+{
+ task_isolation_debug_flag = true;
+ return 1;
+}
+__setup("task_isolation_debug", task_isolation_debug_func);
+
+void task_isolation_debug_task(int cpu, struct task_struct *p, const char *type)
+{
+ static DEFINE_RATELIMIT_STATE(console_output, HZ, 1);
+ bool force_debug = false;
+
+ /*
+ * Our caller made sure the task was running on a task isolation
+ * core, but make sure the task has enabled isolation.
+ */
+ if (!(p->task_isolation_flags & PR_TASK_ISOLATION_ENABLE))
+ return;
+
+ /*
+ * Ensure the task is actually in userspace; if it is in kernel
+ * mode, it is expected that it may receive interrupts, and in
+ * any case they don't affect the isolation. Note that there
+ * is a race condition here as a task may have committed
+ * to returning to user space but not yet set the context
+ * tracking state to reflect it, and the check here is before
+ * we trigger the interrupt, so we might fail to warn about a
+ * legitimate interrupt. However, the race window is narrow
+ * and hitting it does not cause any incorrect behavior other
+ * than failing to send the warning.
+ */
+ if (cpu != smp_processor_id() && !context_tracking_cpu_in_user(cpu))
+ return;
+
+ /*
+ * We disable task isolation mode when we deliver a signal
+ * so we won't end up recursing back here again.
+ * If we are in an NMI, we don't try delivering the signal
+ * and instead just treat it as if "debug" mode was enabled,
+ * since that's pretty much all we can do.
+ */
+ if (in_nmi())
+ force_debug = true;
+ else
+ task_isolation_deliver_signal(p, type);
+
+ /*
+ * If (for example) the timer interrupt starts ticking
+ * unexpectedly, we will get an unmanageable flow of output,
+ * so limit to one backtrace per second.
+ */
+ if (force_debug ||
+ (task_isolation_debug_flag && __ratelimit(&console_output))) {
+ pr_err("cpu %d: %s violating task isolation for %s/%d on cpu %d\n",
+ smp_processor_id(), type, p->comm, p->pid, cpu);
+ dump_stack();
+ }
+}
+
+void task_isolation_debug_cpumask(const struct cpumask *mask, const char *type)
+{
+ int cpu, thiscpu = get_cpu();
+
+ /* No need to report on this cpu since we're already in the kernel. */
+ for_each_cpu_and(cpu, mask, task_isolation_map)
+ if (cpu != thiscpu)
+ _task_isolation_debug(cpu, type);
+
+ put_cpu();
+}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5c883fe8e440..21d847bfe5c2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -74,6 +74,7 @@
#include <linux/context_tracking.h>
#include <linux/compiler.h>
#include <linux/frame.h>
+#include <linux/isolation.h>
#include <asm/switch_to.h>
#include <asm/tlb.h>
@@ -663,6 +664,19 @@ bool sched_can_stop_tick(struct rq *rq)
}
#endif /* CONFIG_NO_HZ_FULL */
+#ifdef CONFIG_TASK_ISOLATION
+void _task_isolation_debug(int cpu, const char *type)
+{
+ struct rq *rq = cpu_rq(cpu);
+ struct task_struct *task = try_get_task_struct(&rq->curr);
+
+ if (task) {
+ task_isolation_debug_task(cpu, task, type);
+ put_task_struct(task);
+ }
+}
+#endif
+
void sched_avg_update(struct rq *rq)
{
s64 period = sched_avg_period();
diff --git a/kernel/signal.c b/kernel/signal.c
index 895f547ff66f..40356a06b761 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -639,6 +639,13 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
*/
void signal_wake_up_state(struct task_struct *t, unsigned int state)
{
+ /*
+ * We're delivering a signal anyway, so no need for more
+ * warnings. This also avoids self-deadlock since an IPI to
+ * kick the task would otherwise generate another signal.
+ */
+ task_isolation_set_flags(t, 0);
+
set_tsk_thread_flag(t, TIF_SIGPENDING);
/*
* TASK_WAKEKILL also means wake it up in the stopped/traced/killable
diff --git a/kernel/smp.c b/kernel/smp.c
index 3aa642d39c03..35ca174db581 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -14,6 +14,7 @@
#include <linux/smp.h>
#include <linux/cpu.h>
#include <linux/sched.h>
+#include <linux/isolation.h>
#include "smpboot.h"
@@ -162,8 +163,10 @@ static int generic_exec_single(int cpu, struct call_single_data *csd,
* locking and barrier primitives. Generic code isn't really
* equipped to do the right thing...
*/
- if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
+ if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu))) {
+ task_isolation_debug(cpu, "IPI function");
arch_send_call_function_single_ipi(cpu);
+ }
return 0;
}
@@ -441,6 +444,7 @@ void smp_call_function_many(const struct cpumask *mask,
}
/* Send a message to all CPUs in the map */
+ task_isolation_debug_cpumask(cfd->cpumask, "IPI function");
arch_send_call_function_ipi_mask(cfd->cpumask);
if (wait) {
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 17caf4b63342..2f1065795318 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -26,6 +26,7 @@
#include <linux/smpboot.h>
#include <linux/tick.h>
#include <linux/irq.h>
+#include <linux/isolation.h>
#define CREATE_TRACE_POINTS
#include <trace/events/irq.h>
@@ -319,6 +320,37 @@ asmlinkage __visible void do_softirq(void)
local_irq_restore(flags);
}
+/* Determine whether this IRQ is something task isolation cares about. */
+static void task_isolation_irq(void)
+{
+#ifdef CONFIG_TASK_ISOLATION
+ struct pt_regs *regs;
+
+ if (!context_tracking_cpu_is_enabled())
+ return;
+
+ /*
+ * We have not yet called __irq_enter() and so we haven't
+ * adjusted the hardirq count. This test will allow us to
+ * avoid false positives for nested IRQs.
+ */
+ if (in_interrupt())
+ return;
+
+ /*
+ * If we were already in the kernel, not from an irq but from
+ * a syscall or synchronous exception/fault, this test should
+ * avoid a false positive as well. Note that this requires
+ * architecture support for calling set_irq_regs() prior to
+ * calling irq_enter(), and if it's not done consistently, we
+ * will not consistently avoid false positives here.
+ */
+ regs = get_irq_regs();
+ if (regs && user_mode(regs))
+ task_isolation_debug(smp_processor_id(), "irq");
+#endif
+}
+
/*
* Enter an interrupt context.
*/
@@ -335,6 +367,7 @@ void irq_enter(void)
_local_bh_enable();
}
+ task_isolation_irq();
__irq_enter();
}
--
2.7.2
[toc] | [prev] | [next] | [standalone]
| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 09/14] arch/tile: enable task isolation functionality |
| Message-ID | <s4lYC-3WM-29@gated-at.bofh.it> |
| In reply to | #1459107 |
We add the necessary call to task_isolation_enter() in the
prepare_exit_to_usermode() routine. We already unconditionally
call into this routine if TIF_NOHZ is set, since that's where
we do the user_enter() call.
We add calls to task_isolation_quiet_exception() in places
where exceptions may not generate signals to the application.
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
arch/tile/Kconfig | 1 +
arch/tile/include/asm/thread_info.h | 4 +++-
arch/tile/kernel/process.c | 9 +++++++++
arch/tile/kernel/ptrace.c | 7 +++++++
arch/tile/kernel/single_step.c | 7 +++++++
arch/tile/kernel/smp.c | 26 ++++++++++++++------------
arch/tile/kernel/unaligned.c | 4 ++++
arch/tile/mm/fault.c | 13 ++++++++++++-
arch/tile/mm/homecache.c | 2 ++
9 files changed, 59 insertions(+), 14 deletions(-)
diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 4820a02838ac..937cfe4cbb5b 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -18,6 +18,7 @@ config TILE
select GENERIC_STRNCPY_FROM_USER
select GENERIC_STRNLEN_USER
select HAVE_ARCH_SECCOMP_FILTER
+ select HAVE_ARCH_TASK_ISOLATION
select HAVE_ARCH_TRACEHOOK
select HAVE_CONTEXT_TRACKING
select HAVE_DEBUG_BUGVERBOSE
diff --git a/arch/tile/include/asm/thread_info.h b/arch/tile/include/asm/thread_info.h
index b7659b8f1117..8fe17c7e872e 100644
--- a/arch/tile/include/asm/thread_info.h
+++ b/arch/tile/include/asm/thread_info.h
@@ -126,6 +126,7 @@ extern void _cpu_idle(void);
#define TIF_SYSCALL_TRACEPOINT 9 /* syscall tracepoint instrumentation */
#define TIF_POLLING_NRFLAG 10 /* idle is polling for TIF_NEED_RESCHED */
#define TIF_NOHZ 11 /* in adaptive nohz mode */
+#define TIF_TASK_ISOLATION 12 /* in task isolation mode */
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
@@ -139,11 +140,12 @@ extern void _cpu_idle(void);
#define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
#define _TIF_NOHZ (1<<TIF_NOHZ)
+#define _TIF_TASK_ISOLATION (1<<TIF_TASK_ISOLATION)
/* Work to do as we loop to exit to user space. */
#define _TIF_WORK_MASK \
(_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
- _TIF_ASYNC_TLB | _TIF_NOTIFY_RESUME)
+ _TIF_ASYNC_TLB | _TIF_NOTIFY_RESUME | _TIF_TASK_ISOLATION)
/* Work to do on any return to user space. */
#define _TIF_ALLWORK_MASK \
diff --git a/arch/tile/kernel/process.c b/arch/tile/kernel/process.c
index a465d8372edd..bbe1d29b242f 100644
--- a/arch/tile/kernel/process.c
+++ b/arch/tile/kernel/process.c
@@ -29,6 +29,7 @@
#include <linux/signal.h>
#include <linux/delay.h>
#include <linux/context_tracking.h>
+#include <linux/isolation.h>
#include <asm/stack.h>
#include <asm/switch_to.h>
#include <asm/homecache.h>
@@ -496,9 +497,17 @@ void prepare_exit_to_usermode(struct pt_regs *regs, u32 thread_info_flags)
tracehook_notify_resume(regs);
}
+ if (thread_info_flags & _TIF_TASK_ISOLATION)
+ task_isolation_enter();
+
local_irq_disable();
thread_info_flags = READ_ONCE(current_thread_info()->flags);
+ /* Clear task isolation from cached_flags manually. */
+ if ((thread_info_flags & _TIF_TASK_ISOLATION) &&
+ task_isolation_ready())
+ thread_info_flags &= ~_TIF_TASK_ISOLATION;
+
} while (thread_info_flags & _TIF_WORK_MASK);
if (thread_info_flags & _TIF_SINGLESTEP) {
diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c
index d89b7011667c..b3f8dffcd9ae 100644
--- a/arch/tile/kernel/ptrace.c
+++ b/arch/tile/kernel/ptrace.c
@@ -23,6 +23,7 @@
#include <linux/elf.h>
#include <linux/tracehook.h>
#include <linux/context_tracking.h>
+#include <linux/isolation.h>
#include <asm/traps.h>
#include <arch/chip.h>
@@ -261,6 +262,12 @@ int do_syscall_trace_enter(struct pt_regs *regs)
return -1;
}
+ /* In isolation mode, we may prevent the syscall from running. */
+ if (work & _TIF_TASK_ISOLATION) {
+ if (task_isolation_syscall(regs->regs[TREG_SYSCALL_NR]) == -1)
+ return -1;
+ }
+
if (secure_computing(NULL) == -1)
return -1;
diff --git a/arch/tile/kernel/single_step.c b/arch/tile/kernel/single_step.c
index 862973074bf9..b48da9860b80 100644
--- a/arch/tile/kernel/single_step.c
+++ b/arch/tile/kernel/single_step.c
@@ -23,6 +23,7 @@
#include <linux/types.h>
#include <linux/err.h>
#include <linux/prctl.h>
+#include <linux/isolation.h>
#include <asm/cacheflush.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
@@ -320,6 +321,9 @@ void single_step_once(struct pt_regs *regs)
int size = 0, sign_ext = 0; /* happy compiler */
int align_ctl;
+ /* No signal was generated, but notify task-isolation tasks. */
+ task_isolation_quiet_exception("single step at %#lx", regs->pc);
+
align_ctl = unaligned_fixup;
switch (task_thread_info(current)->align_ctl) {
case PR_UNALIGN_NOPRINT:
@@ -767,6 +771,9 @@ void single_step_once(struct pt_regs *regs)
unsigned long *ss_pc = this_cpu_ptr(&ss_saved_pc);
unsigned long control = __insn_mfspr(SPR_SINGLE_STEP_CONTROL_K);
+ /* No signal was generated, but notify task-isolation tasks. */
+ task_isolation_quiet_exception("single step at %#lx", regs->pc);
+
*ss_pc = regs->pc;
control |= SPR_SINGLE_STEP_CONTROL_1__CANCELED_MASK;
control |= SPR_SINGLE_STEP_CONTROL_1__INHIBIT_MASK;
diff --git a/arch/tile/kernel/smp.c b/arch/tile/kernel/smp.c
index 07e3ff5cc740..d610322026d0 100644
--- a/arch/tile/kernel/smp.c
+++ b/arch/tile/kernel/smp.c
@@ -20,6 +20,7 @@
#include <linux/irq.h>
#include <linux/irq_work.h>
#include <linux/module.h>
+#include <linux/isolation.h>
#include <asm/cacheflush.h>
#include <asm/homecache.h>
@@ -181,10 +182,11 @@ void flush_icache_range(unsigned long start, unsigned long end)
struct ipi_flush flush = { start, end };
/* If invoked with irqs disabled, we can not issue IPIs. */
- if (irqs_disabled())
+ if (irqs_disabled()) {
+ task_isolation_debug_cpumask(task_isolation_map, "icache flush");
flush_remote(0, HV_FLUSH_EVICT_L1I, NULL, 0, 0, 0,
NULL, NULL, 0);
- else {
+ } else {
preempt_disable();
on_each_cpu(ipi_flush_icache_range, &flush, 1);
preempt_enable();
@@ -258,10 +260,8 @@ void __init ipi_init(void)
#if CHIP_HAS_IPI()
-void smp_send_reschedule(int cpu)
+static void __smp_send_reschedule(int cpu)
{
- WARN_ON(cpu_is_offline(cpu));
-
/*
* We just want to do an MMIO store. The traditional writeq()
* functions aren't really correct here, since they're always
@@ -273,15 +273,17 @@ void smp_send_reschedule(int cpu)
#else
-void smp_send_reschedule(int cpu)
+static void __smp_send_reschedule(int cpu)
{
- HV_Coord coord;
-
- WARN_ON(cpu_is_offline(cpu));
-
- coord.y = cpu_y(cpu);
- coord.x = cpu_x(cpu);
+ HV_Coord coord = { .y = cpu_y(cpu), .x = cpu_x(cpu) };
hv_trigger_ipi(coord, IRQ_RESCHEDULE);
}
#endif /* CHIP_HAS_IPI() */
+
+void smp_send_reschedule(int cpu)
+{
+ WARN_ON(cpu_is_offline(cpu));
+ task_isolation_debug(cpu, "reschedule IPI");
+ __smp_send_reschedule(cpu);
+}
diff --git a/arch/tile/kernel/unaligned.c b/arch/tile/kernel/unaligned.c
index 9772a3554282..0335f7cd81f4 100644
--- a/arch/tile/kernel/unaligned.c
+++ b/arch/tile/kernel/unaligned.c
@@ -25,6 +25,7 @@
#include <linux/module.h>
#include <linux/compat.h>
#include <linux/prctl.h>
+#include <linux/isolation.h>
#include <asm/cacheflush.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
@@ -1545,6 +1546,9 @@ void do_unaligned(struct pt_regs *regs, int vecnum)
return;
}
+ /* No signal was generated, but notify task-isolation tasks. */
+ task_isolation_quiet_exception("unaligned JIT at %#lx", regs->pc);
+
if (!info->unalign_jit_base) {
void __user *user_page;
diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index beba986589e5..9bd3600092dc 100644
--- a/arch/tile/mm/fault.c
+++ b/arch/tile/mm/fault.c
@@ -35,6 +35,7 @@
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>
+#include <linux/isolation.h>
#include <asm/pgalloc.h>
#include <asm/sections.h>
@@ -308,8 +309,13 @@ static int handle_page_fault(struct pt_regs *regs,
*/
pgd = get_current_pgd();
if (handle_migrating_pte(pgd, fault_num, address, regs->pc,
- is_kernel_mode, write))
+ is_kernel_mode, write)) {
+ /* No signal was generated, but notify task-isolation tasks. */
+ if (!is_kernel_mode)
+ task_isolation_quiet_exception("migration fault at %#lx",
+ address);
return 1;
+ }
si_code = SEGV_MAPERR;
@@ -479,6 +485,11 @@ good_area:
#endif
up_read(&mm->mmap_sem);
+
+ /* No signal was generated, but notify task-isolation tasks. */
+ if (flags & FAULT_FLAG_USER)
+ task_isolation_quiet_exception("page fault at %#lx", address);
+
return 1;
/*
diff --git a/arch/tile/mm/homecache.c b/arch/tile/mm/homecache.c
index 40ca30a9fee3..2fe368599df6 100644
--- a/arch/tile/mm/homecache.c
+++ b/arch/tile/mm/homecache.c
@@ -31,6 +31,7 @@
#include <linux/smp.h>
#include <linux/module.h>
#include <linux/hugetlb.h>
+#include <linux/isolation.h>
#include <asm/page.h>
#include <asm/sections.h>
@@ -83,6 +84,7 @@ static void hv_flush_update(const struct cpumask *cache_cpumask,
* Don't bother to update atomically; losing a count
* here is not that critical.
*/
+ task_isolation_debug_cpumask(&mask, "remote cache/TLB flush");
for_each_cpu(cpu, &mask)
++per_cpu(irq_stat, cpu).irq_hv_flush_count;
}
--
2.7.2
[toc] | [prev] | [next] | [standalone]
| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 04/14] task_isolation: add initial support |
| Message-ID | <s4lYC-3WM-33@gated-at.bofh.it> |
| In reply to | #1459107 |
The existing nohz_full mode is designed as a "soft" isolation mode
that makes tradeoffs to minimize userspace interruptions while
still attempting to avoid overheads in the kernel entry/exit path,
to provide 100% kernel semantics, etc.
However, some applications require a "hard" commitment from the
kernel to avoid interruptions, in particular userspace device driver
style applications, such as high-speed networking code.
This change introduces a framework to allow applications
to elect to have the "hard" semantics as needed, specifying
prctl(PR_SET_TASK_ISOLATION, PR_TASK_ISOLATION_ENABLE) to do so.
Subsequent commits will add additional flags and additional
semantics.
The kernel must be built with the new TASK_ISOLATION Kconfig flag
to enable this mode, and the kernel booted with an appropriate
task_isolation=CPULIST boot argument, which enables nohz_full and
isolcpus as well. The "task_isolation" state is then indicated by
setting a new task struct field, task_isolation_flag, to the value
passed by prctl(), and also setting a TIF_TASK_ISOLATION bit in
thread_info flags. When task isolation is enabled for a task, and it
is returning to userspace on a task isolation core, it calls the
new task_isolation_ready() / task_isolation_enter() routines to
take additional actions to help the task avoid being interrupted
in the future.
The task_isolation_ready() call is invoked when TIF_TASK_ISOLATION is
set in prepare_exit_to_usermode() or its architectural equivalent,
and forces the loop to retry if the system is not ready. It is
called with interrupts disabled and inspects the kernel state
to determine if it is safe to return into an isolated state.
In particular, if it sees that the scheduler tick is still enabled,
it reports that it is not yet safe.
Each time through the loop of TIF work to do, if TIF_TASK_ISOLATION
is set, we call the new task_isolation_enter() routine. This
takes any actions that might avoid a future interrupt to the core,
such as a worker thread being scheduled that could be quiesced now
(e.g. the vmstat worker) or a future IPI to the core to clean up some
state that could be cleaned up now (e.g. the mm lru per-cpu cache).
In addition, it reqeusts rescheduling if the scheduler dyntick is
still running.
Once the task has returned to userspace after issuing the prctl(),
if it enters the kernel again via system call, page fault, or any
of a number of other synchronous traps, the kernel will kill it
with SIGKILL. For system calls, this test is performed immediately
before the SECCOMP test and causes the syscall to return immediately
with ENOSYS.
To allow the state to be entered and exited, the syscall checking
test ignores the prctl() syscall so that we can clear the bit again
later, and ignores exit/exit_group to allow exiting the task without
a pointless signal killing you as you try to do so.
A new /sys/devices/system/cpu/task_isolation pseudo-file is added,
parallel to the comparable nohz_full file.
Separate patches that follow provide these changes for x86, tile,
and arm64.
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
Documentation/kernel-parameters.txt | 8 ++
drivers/base/cpu.c | 18 +++
include/linux/isolation.h | 60 ++++++++++
include/linux/sched.h | 3 +
include/linux/tick.h | 2 +
include/uapi/linux/prctl.h | 5 +
init/Kconfig | 27 +++++
kernel/Makefile | 1 +
kernel/fork.c | 3 +
kernel/isolation.c | 217 ++++++++++++++++++++++++++++++++++++
kernel/signal.c | 8 ++
kernel/sys.c | 9 ++
kernel/time/tick-sched.c | 36 +++---
13 files changed, 384 insertions(+), 13 deletions(-)
create mode 100644 include/linux/isolation.h
create mode 100644 kernel/isolation.c
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 46c030a49186..7f1336b50dcc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3943,6 +3943,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
neutralize any effect of /proc/sys/kernel/sysrq.
Useful for debugging.
+ task_isolation= [KNL]
+ In kernels built with CONFIG_TASK_ISOLATION=y, set
+ the specified list of CPUs where cpus will be able
+ to use prctl(PR_SET_TASK_ISOLATION) to set up task
+ isolation mode. Setting this boot flag implicitly
+ also sets up nohz_full and isolcpus mode for the
+ listed set of cpus.
+
tcpmhash_entries= [KNL,NET]
Set the number of tcp_metrics_hash slots.
Default value is 8192 or 16384 depending on total
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 691eeea2f19a..eaf40f4264ee 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -17,6 +17,7 @@
#include <linux/of.h>
#include <linux/cpufeature.h>
#include <linux/tick.h>
+#include <linux/isolation.h>
#include "base.h"
@@ -290,6 +291,20 @@ static ssize_t print_cpus_nohz_full(struct device *dev,
static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
#endif
+#ifdef CONFIG_TASK_ISOLATION
+static ssize_t print_cpus_task_isolation(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ int n = 0, len = PAGE_SIZE-2;
+
+ n = scnprintf(buf, len, "%*pbl\n", cpumask_pr_args(task_isolation_map));
+
+ return n;
+}
+static DEVICE_ATTR(task_isolation, 0444, print_cpus_task_isolation, NULL);
+#endif
+
static void cpu_device_release(struct device *dev)
{
/*
@@ -460,6 +475,9 @@ static struct attribute *cpu_root_attrs[] = {
#ifdef CONFIG_NO_HZ_FULL
&dev_attr_nohz_full.attr,
#endif
+#ifdef CONFIG_TASK_ISOLATION
+ &dev_attr_task_isolation.attr,
+#endif
#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
&dev_attr_modalias.attr,
#endif
diff --git a/include/linux/isolation.h b/include/linux/isolation.h
new file mode 100644
index 000000000000..d9288b85b41f
--- /dev/null
+++ b/include/linux/isolation.h
@@ -0,0 +1,60 @@
+/*
+ * Task isolation related global functions
+ */
+#ifndef _LINUX_ISOLATION_H
+#define _LINUX_ISOLATION_H
+
+#include <linux/tick.h>
+#include <linux/prctl.h>
+
+#ifdef CONFIG_TASK_ISOLATION
+
+/* cpus that are configured to support task isolation */
+extern cpumask_var_t task_isolation_map;
+
+extern int task_isolation_init(void);
+
+static inline bool task_isolation_possible(int cpu)
+{
+ return task_isolation_map != NULL &&
+ cpumask_test_cpu(cpu, task_isolation_map);
+}
+
+extern int task_isolation_set(unsigned int flags);
+
+extern bool task_isolation_ready(void);
+extern void task_isolation_enter(void);
+
+static inline void task_isolation_set_flags(struct task_struct *p,
+ unsigned int flags)
+{
+ p->task_isolation_flags = flags;
+
+ if (flags & PR_TASK_ISOLATION_ENABLE)
+ set_tsk_thread_flag(p, TIF_TASK_ISOLATION);
+ else
+ clear_tsk_thread_flag(p, TIF_TASK_ISOLATION);
+}
+
+extern int task_isolation_syscall(int nr);
+
+/* Report on exceptions that don't cause a signal for the user process. */
+extern void _task_isolation_quiet_exception(const char *fmt, ...);
+#define task_isolation_quiet_exception(fmt, ...) \
+ do { \
+ if (current_thread_info()->flags & _TIF_TASK_ISOLATION) \
+ _task_isolation_quiet_exception(fmt, ## __VA_ARGS__); \
+ } while (0)
+
+#else
+static inline void task_isolation_init(void) { }
+static inline bool task_isolation_possible(int cpu) { return false; }
+static inline bool task_isolation_ready(void) { return true; }
+static inline void task_isolation_enter(void) { }
+extern inline void task_isolation_set_flags(struct task_struct *p,
+ unsigned int flags) { }
+static inline int task_isolation_syscall(int nr) { return 0; }
+static inline void task_isolation_quiet_exception(const char *fmt, ...) { }
+#endif
+
+#endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 62c68e513e39..77dc12cd4fe8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1923,6 +1923,9 @@ struct task_struct {
#ifdef CONFIG_MMU
struct task_struct *oom_reaper_list;
#endif
+#ifdef CONFIG_TASK_ISOLATION
+ unsigned int task_isolation_flags;
+#endif
/* CPU-specific state of this task */
struct thread_struct thread;
/*
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 62be0786d6d0..fbd81e322860 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -235,6 +235,8 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
extern void tick_nohz_full_kick_cpu(int cpu);
extern void __tick_nohz_task_switch(void);
+extern void tick_nohz_full_add_cpus(const struct cpumask *mask);
+extern bool can_stop_my_full_tick(void);
#else
static inline int housekeeping_any_cpu(void)
{
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index a8d0759a9e40..2a49d0d2940a 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -197,4 +197,9 @@ struct prctl_mm_map {
# define PR_CAP_AMBIENT_LOWER 3
# define PR_CAP_AMBIENT_CLEAR_ALL 4
+/* Enable/disable or query task_isolation mode for TASK_ISOLATION kernels. */
+#define PR_SET_TASK_ISOLATION 48
+#define PR_GET_TASK_ISOLATION 49
+# define PR_TASK_ISOLATION_ENABLE (1 << 0)
+
#endif /* _LINUX_PRCTL_H */
diff --git a/init/Kconfig b/init/Kconfig
index 69886493ff1e..85a4b6dd26f2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -786,6 +786,33 @@ config RCU_EXPEDITE_BOOT
endmenu # "RCU Subsystem"
+config HAVE_ARCH_TASK_ISOLATION
+ bool
+
+config TASK_ISOLATION
+ bool "Provide hard CPU isolation from the kernel on demand"
+ depends on NO_HZ_FULL && HAVE_ARCH_TASK_ISOLATION
+ help
+ Allow userspace processes to place themselves on task_isolation
+ cores and run prctl(PR_SET_TASK_ISOLATION) to "isolate"
+ themselves from the kernel. Prior to returning to userspace,
+ isolated tasks will arrange that no future kernel
+ activity will interrupt the task while the task is running
+ in userspace. By default, attempting to re-enter the kernel
+ while in this mode will cause the task to be terminated
+ with a signal; you must explicitly use prctl() to disable
+ task isolation before resuming normal use of the kernel.
+
+ This "hard" isolation from the kernel is required for
+ userspace tasks that are running hard real-time tasks in
+ userspace, such as a 10 Gbit network driver in userspace.
+ Without this option, but with NO_HZ_FULL enabled, the kernel
+ will make a best-faith, "soft" effort to shield a single userspace
+ process from interrupts, but makes no guarantees.
+
+ You should say "N" unless you are intending to run a
+ high-performance userspace driver or similar task.
+
config BUILD_BIN2C
bool
default n
diff --git a/kernel/Makefile b/kernel/Makefile
index e2ec54e2b952..91ff1615f4d6 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -112,6 +112,7 @@ obj-$(CONFIG_TORTURE_TEST) += torture.o
obj-$(CONFIG_MEMBARRIER) += membarrier.o
obj-$(CONFIG_HAS_IOMEM) += memremap.o
+obj-$(CONFIG_TASK_ISOLATION) += isolation.o
$(obj)/configs.o: $(obj)/config_data.h
diff --git a/kernel/fork.c b/kernel/fork.c
index 52e725d4a866..54542266d7a8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -76,6 +76,7 @@
#include <linux/compiler.h>
#include <linux/sysctl.h>
#include <linux/kcov.h>
+#include <linux/isolation.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1533,6 +1534,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
#endif
clear_all_latency_tracing(p);
+ task_isolation_set_flags(p, 0);
+
/* ok, now we should be set up.. */
p->pid = pid_nr(pid);
if (clone_flags & CLONE_THREAD) {
diff --git a/kernel/isolation.c b/kernel/isolation.c
new file mode 100644
index 000000000000..bf3ebb0a727c
--- /dev/null
+++ b/kernel/isolation.c
@@ -0,0 +1,217 @@
+/*
+ * linux/kernel/isolation.c
+ *
+ * Implementation for task isolation.
+ *
+ * Distributed under GPLv2.
+ */
+
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/vmstat.h>
+#include <linux/isolation.h>
+#include <linux/syscalls.h>
+#include <asm/unistd.h>
+#include <asm/syscall.h>
+#include "time/tick-sched.h"
+
+cpumask_var_t task_isolation_map;
+static bool saw_boot_arg;
+
+/*
+ * Isolation requires both nohz and isolcpus support from the scheduler.
+ * We provide a boot flag that enables both for now, and which we can
+ * add other functionality to over time if needed. Note that just
+ * specifying "nohz_full=... isolcpus=..." does not enable task isolation.
+ */
+static int __init task_isolation_setup(char *str)
+{
+ saw_boot_arg = true;
+
+ alloc_bootmem_cpumask_var(&task_isolation_map);
+ if (cpulist_parse(str, task_isolation_map) < 0) {
+ pr_warn("task_isolation: Incorrect cpumask '%s'\n", str);
+ return 1;
+ }
+
+ return 1;
+}
+__setup("task_isolation=", task_isolation_setup);
+
+int __init task_isolation_init(void)
+{
+ /* For offstack cpumask, ensure we allocate an empty cpumask early. */
+ if (!saw_boot_arg) {
+ zalloc_cpumask_var(&task_isolation_map, GFP_KERNEL);
+ return 0;
+ }
+
+ /*
+ * Add our task_isolation cpus to nohz_full and isolcpus. Note
+ * that we are called relatively early in boot, from tick_init();
+ * at this point neither nohz_full nor isolcpus has been used
+ * to configure the system, but isolcpus has been allocated
+ * already in sched_init().
+ */
+ tick_nohz_full_add_cpus(task_isolation_map);
+ cpumask_or(cpu_isolated_map, cpu_isolated_map, task_isolation_map);
+
+ return 0;
+}
+
+/*
+ * Get a snapshot of whether, at this moment, it would be possible to
+ * stop the tick. This test normally requires interrupts disabled since
+ * the condition can change if an interrupt is delivered. However, in
+ * this case we are using it in an advisory capacity to see if there
+ * is anything obviously indicating that the task isolation
+ * preconditions have not been met, so it's OK that in principle it
+ * might not still be true later in the prctl() syscall path.
+ */
+static bool can_stop_my_full_tick_now(void)
+{
+ bool ret;
+
+ local_irq_disable();
+ ret = can_stop_my_full_tick();
+ local_irq_enable();
+ return ret;
+}
+
+/*
+ * This routine controls whether we can enable task-isolation mode.
+ * The task must be affinitized to a single task_isolation core, or
+ * else we return EINVAL. And, it must be at least statically able to
+ * stop the nohz_full tick (e.g., no other schedulable tasks currently
+ * running, no POSIX cpu timers currently set up, etc.); if not, we
+ * return EAGAIN.
+ */
+int task_isolation_set(unsigned int flags)
+{
+ if (flags != 0) {
+ if (cpumask_weight(tsk_cpus_allowed(current)) != 1 ||
+ !task_isolation_possible(raw_smp_processor_id())) {
+ /* Invalid task affinity setting. */
+ return -EINVAL;
+ }
+ if (!can_stop_my_full_tick_now()) {
+ /* System not yet ready for task isolation. */
+ return -EAGAIN;
+ }
+ }
+
+ task_isolation_set_flags(current, flags);
+ return 0;
+}
+
+/*
+ * In task isolation mode we try to return to userspace only after
+ * attempting to make sure we won't be interrupted again. This test
+ * is run with interrupts disabled to test that everything we need
+ * to be true is true before we can return to userspace.
+ */
+bool task_isolation_ready(void)
+{
+ WARN_ON_ONCE(!irqs_disabled());
+
+ return (!lru_add_drain_needed(smp_processor_id()) &&
+ vmstat_idle() &&
+ tick_nohz_tick_stopped());
+}
+
+/*
+ * Each time we try to prepare for return to userspace in a process
+ * with task isolation enabled, we run this code to quiesce whatever
+ * subsystems we can readily quiesce to avoid later interrupts.
+ */
+void task_isolation_enter(void)
+{
+ WARN_ON_ONCE(irqs_disabled());
+
+ /* Drain the pagevecs to avoid unnecessary IPI flushes later. */
+ lru_add_drain();
+
+ /* Quieten the vmstat worker so it won't interrupt us. */
+ quiet_vmstat_sync();
+
+ /*
+ * Request rescheduling unless we are in full dynticks mode.
+ * We would eventually get pre-empted without this, and if
+ * there's another task waiting, it would run; but by
+ * explicitly requesting the reschedule, we may reduce the
+ * latency. We could directly call schedule() here as well,
+ * but since our caller is the standard place where schedule()
+ * is called, we defer to the caller.
+ *
+ * A more substantive approach here would be to use a struct
+ * completion here explicitly, and complete it when we shut
+ * down dynticks, but since we presumably have nothing better
+ * to do on this core anyway, just spinning seems plausible.
+ */
+ if (!tick_nohz_tick_stopped())
+ set_tsk_need_resched(current);
+}
+
+static void task_isolation_deliver_signal(struct task_struct *task,
+ const char *buf)
+{
+ siginfo_t info = {};
+
+ info.si_signo = SIGKILL;
+
+ /*
+ * Report on the fact that isolation was violated for the task.
+ * It may not be the task's fault (e.g. a TLB flush from another
+ * core) but we are not blaming it, just reporting that it lost
+ * its isolation status.
+ */
+ pr_warn("%s/%d: task_isolation mode lost due to %s\n",
+ task->comm, task->pid, buf);
+
+ /* Turn off task isolation mode to avoid further isolation callbacks. */
+ task_isolation_set_flags(task, 0);
+
+ send_sig_info(info.si_signo, &info, task);
+}
+
+/*
+ * This routine is called from any userspace exception that doesn't
+ * otherwise trigger a signal to the user process (e.g. simple page fault).
+ */
+void _task_isolation_quiet_exception(const char *fmt, ...)
+{
+ struct task_struct *task = current;
+ va_list args;
+ char buf[100];
+
+ /* RCU should have been enabled prior to this point. */
+ RCU_LOCKDEP_WARN(!rcu_is_watching(), "kernel entry without RCU");
+
+ va_start(args, fmt);
+ vsnprintf(buf, sizeof(buf), fmt, args);
+ va_end(args);
+
+ task_isolation_deliver_signal(task, buf);
+}
+
+/*
+ * This routine is called from syscall entry (with the syscall number
+ * passed in), and prevents most syscalls from executing and raises a
+ * signal to notify the process.
+ */
+int task_isolation_syscall(int syscall)
+{
+ char buf[20];
+
+ if (syscall == __NR_prctl ||
+ syscall == __NR_exit ||
+ syscall == __NR_exit_group)
+ return 0;
+
+ snprintf(buf, sizeof(buf), "syscall %d", syscall);
+ task_isolation_deliver_signal(current, buf);
+
+ syscall_set_return_value(current, current_pt_regs(),
+ -ERESTARTNOINTR, -1);
+ return -1;
+}
diff --git a/kernel/signal.c b/kernel/signal.c
index af21afc00d08..895f547ff66f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -34,6 +34,7 @@
#include <linux/compat.h>
#include <linux/cn_proc.h>
#include <linux/compiler.h>
+#include <linux/isolation.h>
#define CREATE_TRACE_POINTS
#include <trace/events/signal.h>
@@ -2213,6 +2214,13 @@ relock:
/* Trace actually delivered signals. */
trace_signal_deliver(signr, &ksig->info, ka);
+ /*
+ * Disable task isolation when delivering a signal.
+ * The isolation model requires users to reset task
+ * isolation from the signal handler if desired.
+ */
+ task_isolation_set_flags(current, 0);
+
if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */
continue;
if (ka->sa.sa_handler != SIG_DFL) {
diff --git a/kernel/sys.c b/kernel/sys.c
index 89d5be418157..4df84af425e3 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -41,6 +41,7 @@
#include <linux/syscore_ops.h>
#include <linux/version.h>
#include <linux/ctype.h>
+#include <linux/isolation.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
@@ -2270,6 +2271,14 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_GET_FP_MODE:
error = GET_FP_MODE(me);
break;
+#ifdef CONFIG_TASK_ISOLATION
+ case PR_SET_TASK_ISOLATION:
+ error = task_isolation_set(arg2);
+ break;
+ case PR_GET_TASK_ISOLATION:
+ error = me->task_isolation_flags;
+ break;
+#endif
default:
error = -EINVAL;
break;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 204fdc86863d..a6e29527743e 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -23,6 +23,7 @@
#include <linux/irq_work.h>
#include <linux/posix-timers.h>
#include <linux/context_tracking.h>
+#include <linux/isolation.h>
#include <asm/irq_regs.h>
@@ -205,6 +206,11 @@ static bool can_stop_full_tick(struct tick_sched *ts)
return true;
}
+bool can_stop_my_full_tick(void)
+{
+ return can_stop_full_tick(this_cpu_ptr(&tick_cpu_sched));
+}
+
static void nohz_full_kick_func(struct irq_work *work)
{
/* Empty, the tick restart happens on tick_nohz_irq_exit() */
@@ -407,30 +413,34 @@ static int tick_nohz_cpu_down_callback(struct notifier_block *nfb,
return NOTIFY_OK;
}
-static int tick_nohz_init_all(void)
+void tick_nohz_full_add_cpus(const struct cpumask *mask)
{
- int err = -1;
+ if (!cpumask_weight(mask))
+ return;
-#ifdef CONFIG_NO_HZ_FULL_ALL
- if (!alloc_cpumask_var(&tick_nohz_full_mask, GFP_KERNEL)) {
+ if (tick_nohz_full_mask == NULL &&
+ !zalloc_cpumask_var(&tick_nohz_full_mask, GFP_KERNEL)) {
WARN(1, "NO_HZ: Can't allocate full dynticks cpumask\n");
- return err;
+ return;
}
- err = 0;
- cpumask_setall(tick_nohz_full_mask);
+
+ cpumask_or(tick_nohz_full_mask, tick_nohz_full_mask, mask);
tick_nohz_full_running = true;
-#endif
- return err;
}
void __init tick_nohz_init(void)
{
int cpu;
- if (!tick_nohz_full_running) {
- if (tick_nohz_init_all() < 0)
- return;
- }
+ task_isolation_init();
+
+#ifdef CONFIG_NO_HZ_FULL_ALL
+ if (!tick_nohz_full_running)
+ tick_nohz_full_add_cpus(cpu_possible_mask);
+#endif
+
+ if (!tick_nohz_full_running)
+ return;
if (!alloc_cpumask_var(&housekeeping_mask, GFP_KERNEL)) {
WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n");
--
2.7.2
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| From | Chris Metcalf <cmetcalf@mellanox.com> |
|---|---|
| Date | 2016-08-09 22:40 +0200 |
| Subject | [PATCH v14 07/14] arm64: factor work_pending state machine to C |
| Message-ID | <s4lYC-3WM-27@gated-at.bofh.it> |
| In reply to | #1459107 |
Currently ret_fast_syscall, work_pending, and ret_to_user form an ad-hoc
state machine that can be difficult to reason about due to duplicated
code and a large number of branch targets.
This patch factors the common logic out into the existing
do_notify_resume function, converting the code to C in the process,
making the code more legible.
This patch tries to closely mirror the existing behaviour while using
the usual C control flow primitives. As local_irq_{disable,enable} may
be instrumented, we balance exception entry (where we will almost most
likely enable IRQs) with a call to trace_hardirqs_on just before the
return to userspace.
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
(Note: Will Deacon has said he will look at queueing this separately for 4.9)
arch/arm64/kernel/entry.S | 12 ++++--------
arch/arm64/kernel/signal.c | 36 ++++++++++++++++++++++++++----------
2 files changed, 30 insertions(+), 18 deletions(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 96e4a2b64cc1..4af25bb7f116 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -700,18 +700,13 @@ ret_fast_syscall_trace:
* Ok, we need to do extra processing, enter the slow path.
*/
work_pending:
- tbnz x1, #TIF_NEED_RESCHED, work_resched
- /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */
mov x0, sp // 'regs'
- enable_irq // enable interrupts for do_notify_resume()
bl do_notify_resume
- b ret_to_user
-work_resched:
#ifdef CONFIG_TRACE_IRQFLAGS
- bl trace_hardirqs_off // the IRQs are off here, inform the tracing code
+ bl trace_hardirqs_on // enabled while in userspace
#endif
- bl schedule
-
+ ldr x1, [tsk, #TI_FLAGS] // re-check for single-step
+ b finish_ret_to_user
/*
* "slow" syscall return path.
*/
@@ -720,6 +715,7 @@ ret_to_user:
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
+finish_ret_to_user:
enable_step_tsk x1, x2
kernel_exit 0
ENDPROC(ret_to_user)
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index a8eafdbc7cb8..404dd67080b9 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -402,15 +402,31 @@ static void do_signal(struct pt_regs *regs)
asmlinkage void do_notify_resume(struct pt_regs *regs,
unsigned int thread_flags)
{
- if (thread_flags & _TIF_SIGPENDING)
- do_signal(regs);
-
- if (thread_flags & _TIF_NOTIFY_RESUME) {
- clear_thread_flag(TIF_NOTIFY_RESUME);
- tracehook_notify_resume(regs);
- }
-
- if (thread_flags & _TIF_FOREIGN_FPSTATE)
- fpsimd_restore_current_state();
+ /*
+ * The assembly code enters us with IRQs off, but it hasn't
+ * informed the tracing code of that for efficiency reasons.
+ * Update the trace code with the current status.
+ */
+ trace_hardirqs_off();
+ do {
+ if (thread_flags & _TIF_NEED_RESCHED) {
+ schedule();
+ } else {
+ local_irq_enable();
+
+ if (thread_flags & _TIF_SIGPENDING)
+ do_signal(regs);
+
+ if (thread_flags & _TIF_NOTIFY_RESUME) {
+ clear_thread_flag(TIF_NOTIFY_RESUME);
+ tracehook_notify_resume(regs);
+ }
+
+ if (thread_flags & _TIF_FOREIGN_FPSTATE)
+ fpsimd_restore_current_state();
+ }
+ local_irq_disable();
+ thread_flags = READ_ONCE(current_thread_info()->flags);
+ } while (thread_flags & _TIF_WORK_MASK);
}
--
2.7.2
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