linux-kernel - Re: [PATCH v4 0/6] arm64: Add kernel probes (kprobes) support

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Message-ID: <20150112140918.GD24728@linaro.org>
Date:	Mon, 12 Jan 2015 14:09:19 +0000
From:	Steve Capper <steve.capper@...aro.org>
To:	David Long <dave.long@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>,
	William Cohen <wcohen@...hat.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"Jon Medhurst (Tixy)" <tixy@...aro.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	davem@...emloft.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/6] arm64: Add kernel probes (kprobes) support

On Sat, Jan 10, 2015 at 11:03:15PM -0500, David Long wrote:
> From: "David A. Long" <dave.long@...aro.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, particularly during
> SMP 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.
> 
> 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).

Hi David,
I've left feedback on the patches in the series.

I ran into two major issues:
  1) trampoline_probe_handler had an errant call to:
      kprobes_restore_local_irqflag (this caused crashes for me until
      I removed it).

  2) I couldn't see how kprobe_fault_handler is called.

I've performed my memcpy tests on Juno running 3.19-rc3, and it appears
stable once trampoline_probe_handler is adjusted.

Cheers,
-- 
Steve

> 
> 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
> 
>  arch/arm64/Kconfig                       |   3 +
>  arch/arm64/include/asm/insn.h            |  21 +-
>  arch/arm64/include/asm/kprobes.h         |  61 +++
>  arch/arm64/include/asm/probes.h          |  50 +++
>  arch/arm64/include/asm/ptrace.h          |  32 +-
>  arch/arm64/include/uapi/asm/ptrace.h     |  36 ++
>  arch/arm64/kernel/Makefile               |   3 +
>  arch/arm64/kernel/insn.c                 |  18 +
>  arch/arm64/kernel/kprobes-arm64.c        | 161 +++++++
>  arch/arm64/kernel/kprobes-arm64.h        |  30 ++
>  arch/arm64/kernel/kprobes.c              | 692 +++++++++++++++++++++++++++++++
>  arch/arm64/kernel/kprobes.h              |  30 ++
>  arch/arm64/kernel/probes-condn-check.c   | 122 ++++++
>  arch/arm64/kernel/probes-simulate-insn.c | 174 ++++++++
>  arch/arm64/kernel/probes-simulate-insn.h |  33 ++
>  arch/arm64/kernel/ptrace.c               | 119 ++++++
>  arch/arm64/kernel/vmlinux.lds.S          |   1 +
>  samples/kprobes/kprobe_example.c         |   8 +
>  18 files changed, 1591 insertions(+), 3 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/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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