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Groups > linux.kernel > #1694740 > unrolled thread
| Started by | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| First post | 2017-07-24 16:00 +0200 |
| Last post | 2017-07-25 03:50 +0200 |
| Articles | 3 — 1 participant |
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[PATCH -tip] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code Masami Hiramatsu <mhiramat@kernel.org> - 2017-07-24 16:00 +0200
Re: [PATCH -tip] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code Masami Hiramatsu <mhiramat@kernel.org> - 2017-07-25 02:20 +0200
Re: [PATCH -tip] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code Masami Hiramatsu <mhiramat@kernel.org> - 2017-07-25 03:50 +0200
| From | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| Date | 2017-07-24 16:00 +0200 |
| Subject | [PATCH -tip] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code |
| Message-ID | <u6M3T-5Cy-7@gated-at.bofh.it> |
Since the kernel segment registers are not prepared at the
entry of irq-entry code, if a kprobe on such code is
jump-optimized, accessing per-cpu variables may cause
kernel panic.
However, if the kprobe is not optimized, it kicks int3
exception and set segment registers correctly.
This checks probe-address and if it is in irq-entry code,
it prohibits optimizing such kprobes. This means we can
continuously probing such interrupt handlers by kprobes
but it is not optimized anymore.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reported-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Tested-by: Francis Deslauriers <francis.deslauriers@efficios.com>
---
arch/x86/entry/entry_64.S | 2 +-
arch/x86/include/asm/unwind.h | 1 +
arch/x86/kernel/kprobes/opt.c | 4 ++--
arch/x86/kernel/unwind_frame.c | 4 ++--
4 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index aa58155..9652c34 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -766,7 +766,7 @@ apicinterrupt3 \num trace(\sym) smp_trace(\sym)
#endif
/* Make sure APIC interrupt handlers end up in the irqentry section: */
-#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || defined(CONFIG_KPROBES)
# define PUSH_SECTION_IRQENTRY .pushsection .irqentry.text, "ax"
# define POP_SECTION_IRQENTRY .popsection
#else
diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index e667649..a9896fb9 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -28,6 +28,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
bool unwind_next_frame(struct unwind_state *state);
unsigned long unwind_get_return_address(struct unwind_state *state);
+bool in_entry_code(unsigned long ip);
static inline bool unwind_done(struct unwind_state *state)
{
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 69ea0bc..a51c144 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -39,6 +39,7 @@
#include <asm/insn.h>
#include <asm/debugreg.h>
#include <asm/set_memory.h>
+#include <asm/unwind.h>
#include "common.h"
@@ -253,8 +254,7 @@ static int can_optimize(unsigned long paddr)
* Do not optimize in the entry code due to the unstable
* stack handling.
*/
- if ((paddr >= (unsigned long)__entry_text_start) &&
- (paddr < (unsigned long)__entry_text_end))
+ if (in_entry_code(paddr))
return 0;
/* Check there is enough space for a relative jump. */
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index b9389d7..95123ce 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -84,14 +84,14 @@ static size_t regs_size(struct pt_regs *regs)
return sizeof(*regs);
}
-static bool in_entry_code(unsigned long ip)
+bool in_entry_code(unsigned long ip)
{
char *addr = (char *)ip;
if (addr >= __entry_text_start && addr < __entry_text_end)
return true;
-#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || defined(CONFIG_KPROBES)
if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
return true;
#endif
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| From | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| Date | 2017-07-25 02:20 +0200 |
| Subject | Re: [PATCH -tip] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code |
| Message-ID | <u6VJT-400-1@gated-at.bofh.it> |
| In reply to | #1694740 |
On Mon, 24 Jul 2017 14:28:36 +0000 (UTC)
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
> ----- On Jul 24, 2017, at 9:50 AM, Masami Hiramatsu mhiramat@kernel.org wrote:
>
> > Since the kernel segment registers are not prepared at the
> > entry of irq-entry code, if a kprobe on such code is
> > jump-optimized, accessing per-cpu variables may cause
> > kernel panic.
> > However, if the kprobe is not optimized, it kicks int3
> > exception and set segment registers correctly.
> >
> > This checks probe-address and if it is in irq-entry code,
> > it prohibits optimizing such kprobes. This means we can
> > continuously probing such interrupt handlers by kprobes
> > but it is not optimized anymore.
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > Reported-by: Francis Deslauriers <francis.deslauriers@efficios.com>
> > Tested-by: Francis Deslauriers <francis.deslauriers@efficios.com>
> > ---
> > arch/x86/entry/entry_64.S | 2 +-
> > arch/x86/include/asm/unwind.h | 1 +
> > arch/x86/kernel/kprobes/opt.c | 4 ++--
> > arch/x86/kernel/unwind_frame.c | 4 ++--
> > 4 files changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> > index aa58155..9652c34 100644
> > --- a/arch/x86/entry/entry_64.S
> > +++ b/arch/x86/entry/entry_64.S
> > @@ -766,7 +766,7 @@ apicinterrupt3 \num trace(\sym) smp_trace(\sym)
> > #endif
> >
> > /* Make sure APIC interrupt handlers end up in the irqentry section: */
> > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
> > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) ||
> > defined(CONFIG_KPROBES)
> > # define PUSH_SECTION_IRQENTRY .pushsection .irqentry.text, "ax"
> > # define POP_SECTION_IRQENTRY .popsection
> > #else
> > diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
> > index e667649..a9896fb9 100644
> > --- a/arch/x86/include/asm/unwind.h
> > +++ b/arch/x86/include/asm/unwind.h
> > @@ -28,6 +28,7 @@ void __unwind_start(struct unwind_state *state, struct
> > task_struct *task,
> > bool unwind_next_frame(struct unwind_state *state);
> >
> > unsigned long unwind_get_return_address(struct unwind_state *state);
> > +bool in_entry_code(unsigned long ip);
> >
> > static inline bool unwind_done(struct unwind_state *state)
> > {
> > diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
> > index 69ea0bc..a51c144 100644
> > --- a/arch/x86/kernel/kprobes/opt.c
> > +++ b/arch/x86/kernel/kprobes/opt.c
> > @@ -39,6 +39,7 @@
> > #include <asm/insn.h>
> > #include <asm/debugreg.h>
> > #include <asm/set_memory.h>
> > +#include <asm/unwind.h>
> >
> > #include "common.h"
> >
> > @@ -253,8 +254,7 @@ static int can_optimize(unsigned long paddr)
> > * Do not optimize in the entry code due to the unstable
> > * stack handling.
> > */
> > - if ((paddr >= (unsigned long)__entry_text_start) &&
> > - (paddr < (unsigned long)__entry_text_end))
> > + if (in_entry_code(paddr))
> > return 0;
> >
> > /* Check there is enough space for a relative jump. */
> > diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
> > index b9389d7..95123ce 100644
> > --- a/arch/x86/kernel/unwind_frame.c
> > +++ b/arch/x86/kernel/unwind_frame.c
> > @@ -84,14 +84,14 @@ static size_t regs_size(struct pt_regs *regs)
> > return sizeof(*regs);
> > }
> >
> > -static bool in_entry_code(unsigned long ip)
> > +bool in_entry_code(unsigned long ip)
> > {
> > char *addr = (char *)ip;
> >
> > if (addr >= __entry_text_start && addr < __entry_text_end)
> > return true;
> >
> > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
> > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) ||
> > defined(CONFIG_KPROBES)
>
> Hi Masami,
>
> With this patch applied on top of v4.12.3, I can generate a configuration
> with CONFIG_KPROBES=y and CONFIG_FRAME_POINTER=n, which leads to:
>
> arch/x86/built-in.o: In function `can_optimize':
> /home/efficios/git/linux/arch/x86/kernel/kprobes/opt.c:250: undefined reference to `in_entry_code'
>
> (see attached .config)
Oops, right.
> arch/x86/kernel/unwind_frame.c is only compiled when CONFIG_FRAME_POINTER
> is enabled, but CONFIG_KPROBES does not depend on it.
>
> Is unwind_frame.c really where in_entry_code() should be implemented, now
> that its symbol becomes exposed to other compile units ?
At least kprobes needs it. (as far
It seems we can move it in arch/x86/entry/common.c or
somewhere in header. (arm has arch/arm/include/asm/traps.h for
that purpose)
Thanks,
>
> Thanks,
>
> Mathieu
>
>
> > if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
> > return true;
> > #endif
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
--
Masami Hiramatsu <mhiramat@kernel.org>
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| From | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| Date | 2017-07-25 03:50 +0200 |
| Subject | Re: [PATCH -tip] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code |
| Message-ID | <u6X8Z-4OV-3@gated-at.bofh.it> |
| In reply to | #1695295 |
On Tue, 25 Jul 2017 09:15:29 +0900 Masami Hiramatsu <mhiramat@kernel.org> wrote: > > arch/x86/kernel/unwind_frame.c is only compiled when CONFIG_FRAME_POINTER > > is enabled, but CONFIG_KPROBES does not depend on it. > > > > Is unwind_frame.c really where in_entry_code() should be implemented, now > > that its symbol becomes exposed to other compile units ? > > At least kprobes needs it. (as far > It seems we can move it in arch/x86/entry/common.c or > somewhere in header. (arm has arch/arm/include/asm/traps.h for > that purpose) As far as I can see, that code is only for unwinder or kprobes, and only arm/arm64 has similar code. I've decided to make this fix kprobe/opt.c local, since this fix is also needed for stable. I'll send v2 patch soon. Thanks, -- Masami Hiramatsu <mhiramat@kernel.org>
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