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[PATCH v8 0/7] arm64: Add kernel probes (kprobes) support

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  [PATCH v8 0/7] arm64: Add kernel probes (kprobes) support David Long <dave.long@linaro.org> - 2015-08-11 03:00 +0200
    Re: [PATCH v8 0/7] arm64: Add kernel probes (kprobes) support Will Deacon <will.deacon@arm.com> - 2015-08-11 19:00 +0200
      Re: [PATCH v8 0/7] arm64: Add kernel probes (kprobes) support David Long <dave.long@linaro.org> - 2015-08-11 19:10 +0200
        Re: [PATCH v8 0/7] arm64: Add kernel probes (kprobes) support Will Deacon <will.deacon@arm.com> - 2015-08-11 19:40 +0200

#1204663 — [PATCH v8 0/7] arm64: Add kernel probes (kprobes) support

From: "David A. Long" <dave.long@linaro.org>

This patchset is heavily based on Sandeepa Prabhu's ARM v8 kprobes patches,
first seen in October 2013. This version attempts to address concerns raised by
reviewers and also fixes problems discovered during testing.

This patchset adds support for kernel probes(kprobes), jump probes(jprobes)
and return probes(kretprobes) support for ARM64.

The kprobes mechanism makes use of software breakpoint and single stepping
support available in the ARM v8 kernel.

This patch depends on:
	[PATCH 1/2] Move the pt_regs_offset struct definition from arch to common include file
	[PATCH 2/2] Consolidate redundant register/stack access code

Changes since v2 include:

1) Removal of NOP padding in kprobe XOL slots. Slots are now exactly one
instruction long.
2) Disabling of interrupts during execution in single-step mode.
3) Fixing of numerous problems in instruction simulation code (mostly
thanks to Will Cohen).
4) Support for the HAVE_REGS_AND_STACK_ACCESS_API feature is added, to allow
access to kprobes through debugfs.
5) kprobes is *not* enabled in defconfig.
6) Numerous complaints from checkpatch have been cleaned up, although a couple
remain as removing the function pointer typedefs results in ugly code.

Changes since v3 include:

1) Remove table-driven instruction parsing and replace with an if statement
calling out to old and new instruction test functions in insn.c.
2) I removed the addition of orig_x0 to ptrace.h.
3) Reorder the patches.
4) Replace the previous interrupt disabling (from Will Cohen) with
an improved solution (from Steve Capper).

Changes since v4 include:

1) Added insn.c functions to detect exception instructions and DAIF
   read/write instructions, and use them to reject probing same.
2) Changed adr detect function to also recognize adrp. Reject both.
3) Added missing __kprobes for some new functions.
4) Added call to kprobes_fault_handler from mm do_page_fault.
5) Reject all non-simulated branch/ret instructions, not just those
   that use an immediate offset.
6) Moved software breakpoint definitions into debug-monitors.h.
7) Removed "!XIP_KERNEL" from Kconfig.
8) changed kprobes_condition_check_t and kprobes_prepare_t to probes_*,
   for future sharing with uprobes.
9) Removed bogus call to kprobes_restore_local_irqflag() from 
   trampoline_probe_handler().

Changes since v5 include:

1) Replaced installation of breakpoint hook with direct call from the
handlers in debug-monitors.c, as requested.
2) Reject probing of instructions that read the interrupt mask, in
addition to instructions that set it.
3) Cleaned up comments describing usage of Debug Mask.
4) Added KPROBE_REENTER case in reenter_kprobe.
5) Corrected the ifdef'd definitions for notify_page_fault() to be
consistent when KPROBES is not configed.
6) Changed "cpsr" to "pstate" for HAVE_REGS_AND_STACK_ACCESS_API feature.
7) Added back in missing new files in previous patch.
8) Changed two instances of pr_warning() to pr_warn().

Note that there seems to be at least a potential issue with kprobes
on multiple (possibly all) platforms having to do with use of kfree
inside of the kretprobes trampoline handler.  This has manifested
occasionally in systemtap testing on arm64.  There does not appear to
be an simple solution to the problem.

Changes since v6 include:

1) New trampoline code from Will Cohen fixes the occasional failure seen
when processing kretprobes by replacing the software breakpoint with
assembly code to implement the return to the original execution stream.
2) Changed ip0, ip1, fp, and lr to plain numbered registers for purposes
of recognizing them as an ascii string in the stack/reg access code.
3) Removed orig_x0.
4) Moved ARM_x* defines from arch/arm64/include/uapi/asm/ptrace.h to
arch/arm64/kernel/ptrace.c.

Changes since v7 include:

1) Move trampoline entry/return code into separate ".S" file instead
of making it a macro in a header file.
2) Add missing register name definitions in asm-offsets.c and use them
in place of hard-coded integer offsets in the trampoline code.
3) Correct the values used to decode MSR immediate instructions, in insn.h.
4) Remove the currently unused simulate_none() function.

David A. Long (2):
  arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature
  arm64: Add more test functions to insn.c

Sandeepa Prabhu (4):
  arm64: Kprobes with single stepping support
  arm64: kprobes instruction simulation support
  arm64: Add kernel return probes support (kretprobes)
  kprobes: Add arm64 case in kprobe example module

William Cohen (1):
  arm64: Add trampoline code for kretprobes

 arch/arm64/Kconfig                       |   3 +
 arch/arm64/include/asm/debug-monitors.h  |   5 +
 arch/arm64/include/asm/insn.h            |  18 +
 arch/arm64/include/asm/kprobes.h         |  64 +++
 arch/arm64/include/asm/probes.h          |  50 +++
 arch/arm64/include/asm/ptrace.h          |  28 +-
 arch/arm64/kernel/Makefile               |   4 +
 arch/arm64/kernel/asm-offsets.c          |  22 ++
 arch/arm64/kernel/debug-monitors.c       |  35 +-
 arch/arm64/kernel/insn.c                 |  28 ++
 arch/arm64/kernel/kprobes-arm64.c        | 166 ++++++++
 arch/arm64/kernel/kprobes-arm64.h        |  30 ++
 arch/arm64/kernel/kprobes.c              | 644 +++++++++++++++++++++++++++++++
 arch/arm64/kernel/kprobes.h              |  24 ++
 arch/arm64/kernel/kprobes_trampoline.S   |  61 +++
 arch/arm64/kernel/probes-condn-check.c   | 122 ++++++
 arch/arm64/kernel/probes-simulate-insn.c | 170 ++++++++
 arch/arm64/kernel/probes-simulate-insn.h |  32 ++
 arch/arm64/kernel/ptrace.c               |  77 ++++
 arch/arm64/kernel/vmlinux.lds.S          |   1 +
 arch/arm64/mm/fault.c                    |  25 ++
 samples/kprobes/kprobe_example.c         |   8 +
 22 files changed, 1606 insertions(+), 11 deletions(-)
 create mode 100644 arch/arm64/include/asm/kprobes.h
 create mode 100644 arch/arm64/include/asm/probes.h
 create mode 100644 arch/arm64/kernel/kprobes-arm64.c
 create mode 100644 arch/arm64/kernel/kprobes-arm64.h
 create mode 100644 arch/arm64/kernel/kprobes.c
 create mode 100644 arch/arm64/kernel/kprobes.h
 create mode 100644 arch/arm64/kernel/kprobes_trampoline.S
 create mode 100644 arch/arm64/kernel/probes-condn-check.c
 create mode 100644 arch/arm64/kernel/probes-simulate-insn.c
 create mode 100644 arch/arm64/kernel/probes-simulate-insn.h

-- 
1.8.1.2

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#1205278

Hi David,

On Tue, Aug 11, 2015 at 01:52:37AM +0100, David Long wrote:
> From: "David A. Long" <dave.long@linaro.org>
> 
> This patchset is heavily based on Sandeepa Prabhu's ARM v8 kprobes patches,
> first seen in October 2013. This version attempts to address concerns raised by
> reviewers and also fixes problems discovered during testing.
> 
> This patchset adds support for kernel probes(kprobes), jump probes(jprobes)
> and return probes(kretprobes) support for ARM64.
> 
> The kprobes mechanism makes use of software breakpoint and single stepping
> support available in the ARM v8 kernel.
> 
> This patch depends on:
> 	[PATCH 1/2] Move the pt_regs_offset struct definition from arch to common include file
> 	[PATCH 2/2] Consolidate redundant register/stack access code

Are these two queued somewhere? This series doesn't even build without
them.

Will
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#1205286

On 08/11/15 12:56, Will Deacon wrote:
> Hi David,
>
> On Tue, Aug 11, 2015 at 01:52:37AM +0100, David Long wrote:
>> From: "David A. Long" <dave.long@linaro.org>
>>
>> This patchset is heavily based on Sandeepa Prabhu's ARM v8 kprobes patches,
>> first seen in October 2013. This version attempts to address concerns raised by
>> reviewers and also fixes problems discovered during testing.
>>
>> This patchset adds support for kernel probes(kprobes), jump probes(jprobes)
>> and return probes(kretprobes) support for ARM64.
>>
>> The kprobes mechanism makes use of software breakpoint and single stepping
>> support available in the ARM v8 kernel.
>>
>> This patch depends on:
>> 	[PATCH 1/2] Move the pt_regs_offset struct definition from arch to common include file
>> 	[PATCH 2/2] Consolidate redundant register/stack access code
>
> Are these two queued somewhere? This series doesn't even build without
> them.
>
> Will
>

I posted the last revision of that on July 27.  I don't know if they're 
"queued" somewhere.  They do affect multiple architectures so I'm not 
certain where they would get queued. They also live in a branch in my 
own Linaro repo.

Was there a better way for me to deal with this dependency?  I was 
reluctant to make this into one patch set as the other patch really does 
stand alone as a useful fix.

-dl

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#1205319

On Tue, Aug 11, 2015 at 06:03:46PM +0100, David Long wrote:
> On 08/11/15 12:56, Will Deacon wrote:
> > On Tue, Aug 11, 2015 at 01:52:37AM +0100, David Long wrote:
> >> From: "David A. Long" <dave.long@linaro.org>
> >>
> >> This patchset is heavily based on Sandeepa Prabhu's ARM v8 kprobes patches,
> >> first seen in October 2013. This version attempts to address concerns raised by
> >> reviewers and also fixes problems discovered during testing.
> >>
> >> This patchset adds support for kernel probes(kprobes), jump probes(jprobes)
> >> and return probes(kretprobes) support for ARM64.
> >>
> >> The kprobes mechanism makes use of software breakpoint and single stepping
> >> support available in the ARM v8 kernel.
> >>
> >> This patch depends on:
> >> 	[PATCH 1/2] Move the pt_regs_offset struct definition from arch to common include file
> >> 	[PATCH 2/2] Consolidate redundant register/stack access code
> >
> > Are these two queued somewhere? This series doesn't even build without
> > them.
> 
> I posted the last revision of that on July 27.  I don't know if they're 
> "queued" somewhere.  They do affect multiple architectures so I'm not 
> certain where they would get queued. They also live in a branch in my 
> own Linaro repo.

Well they're not in linux-next, so I guess they're not currently destined
for mainline :(

> Was there a better way for me to deal with this dependency?  I was 
> reluctant to make this into one patch set as the other patch really does 
> stand alone as a useful fix.

I agree (well, it's a cleanup not a fix). Perhaps it's worth reposting
them with akpm also on Cc, as he sometimes picks up tree-wide patches
like that.

Will
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