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Date: Mon, 22 Mar 2021 15:43:16 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...nel.org>, X86 ML <x86@...nel.org>,
Daniel Xu <dxu@...uu.xyz>, linux-kernel@...r.kernel.org,
bpf@...r.kernel.org, kuba@...nel.org, mingo@...hat.com,
ast@...nel.org, tglx@...utronix.de, kernel-team@...com, yhs@...com,
Josh Poimboeuf <jpoimboe@...hat.com>,
linux-ia64@...r.kernel.org
Subject: Re: [PATCH -tip v3 00/12] kprobes: Fix stacktrace with kretprobes
on x86
Oops, please ignore this. I missed updating the version.
Thanks,
On Mon, 22 Mar 2021 15:36:46 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:
> Hello,
>
> Here is the 4th version of the series to fix the stacktrace with kretprobe
> on x86. After merging this, I'll fix other architectures.
>
> The previous version is;
>
> https://lore.kernel.org/bpf/161615650355.306069.17260992641363840330.stgit@devnote2/
>
> This version fixes some build warnings/errors and a bug on arm. (I think
> arm's kretprobe implementation is a bit odd. anyway, that is off topic.)
> [5/12] fixes objtool warning when CONFIG_FRAME_POINTER=y. [7/12] fixes a
> build error on ia64. And add [8/12] for avoiding stack corruption by
> instruction_pointer_set() in kretprobe_trampoline_handler on arm.
>
> With this series, unwinder can unwind stack correctly from ftrace as below;
>
> # cd /sys/kernel/debug/tracing
> # echo > trace
> # echo r vfs_read >> kprobe_events
> # echo r full_proxy_read >> kprobe_events
> # echo traceoff:1 > events/kprobes/r_vfs_read_0/trigger
> # echo stacktrace:1 > events/kprobes/r_full_proxy_read_0/trigger
> # echo 1 > events/kprobes/enable
> # echo 1 > options/sym-offset
> # cat /sys/kernel/debug/kprobes/list
> ffffffff8133b740 r full_proxy_read+0x0 [FTRACE]
> ffffffff812560b0 r vfs_read+0x0 [FTRACE]
> # echo 0 > events/kprobes/enable
> # cat trace
> # tracer: nop
> #
> # entries-in-buffer/entries-written: 3/3 #P:8
> #
> # _-----=> irqs-off
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / delay
> # TASK-PID CPU# |||| TIMESTAMP FUNCTION
> # | | | |||| | |
> <...>-135 [005] ...1 9.422114: r_full_proxy_read_0: (vfs_read+0xab/0x1a0 <- full_proxy_read)
> <...>-135 [005] ...1 9.422158: <stack trace>
> => kretprobe_trace_func+0x209/0x2f0
> => kretprobe_dispatcher+0x4a/0x70
> => __kretprobe_trampoline_handler+0xca/0x150
> => trampoline_handler+0x44/0x70
> => kretprobe_trampoline+0x2a/0x50
> => vfs_read+0xab/0x1a0
> => ksys_read+0x5f/0xe0
> => do_syscall_64+0x33/0x40
> => entry_SYSCALL_64_after_hwframe+0x44/0xae
> => 0
>
> This shows the double return probes (vfs_read and full_proxy_read) on the stack
> correctly unwinded. (vfs_read was called from ksys_read+0x5f and full_proxy_read
> was called from vfs_read+0xab)
>
> This actually changes the kretprobe behavisor a bit, now the instraction pointer in
> the pt_regs passed to kretprobe user handler is correctly set the real return
> address. So user handlers can get it via instruction_pointer() API.
>
> You can also get this series from
> git://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/kretprobe-stackfix-v4
>
>
> Thank you,
>
> ---
>
> Josh Poimboeuf (1):
> x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code
>
> Masami Hiramatsu (11):
> ia64: kprobes: Fix to pass correct trampoline address to the handler
> kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor()
> kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler()
> kprobes: Add kretprobe_find_ret_addr() for searching return address
> ARC: Add instruction_pointer_set() API
> ia64: Add instruction_pointer_set() API
> arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline
> kprobes: Setup instruction pointer in __kretprobe_trampoline_handler
> x86/kprobes: Push a fake return address at kretprobe_trampoline
> x86/unwind: Recover kretprobe trampoline entry
> tracing: Show kretprobe unknown indicator only for kretprobe_trampoline
>
>
> arch/arc/include/asm/ptrace.h | 5 ++
> arch/arc/kernel/kprobes.c | 2 -
> arch/arm/probes/kprobes/core.c | 5 +-
> arch/arm64/kernel/probes/kprobes.c | 3 -
> arch/csky/kernel/probes/kprobes.c | 2 -
> arch/ia64/include/asm/ptrace.h | 5 ++
> arch/ia64/kernel/kprobes.c | 15 ++---
> arch/mips/kernel/kprobes.c | 3 -
> arch/parisc/kernel/kprobes.c | 4 +
> arch/powerpc/kernel/kprobes.c | 13 -----
> arch/riscv/kernel/probes/kprobes.c | 2 -
> arch/s390/kernel/kprobes.c | 2 -
> arch/sh/kernel/kprobes.c | 2 -
> arch/sparc/kernel/kprobes.c | 2 -
> arch/x86/include/asm/kprobes.h | 1
> arch/x86/include/asm/unwind.h | 17 ++++++
> arch/x86/include/asm/unwind_hints.h | 5 ++
> arch/x86/kernel/kprobes/core.c | 44 ++++++++++++----
> arch/x86/kernel/unwind_frame.c | 4 +
> arch/x86/kernel/unwind_guess.c | 3 -
> arch/x86/kernel/unwind_orc.c | 6 +-
> include/linux/kprobes.h | 41 ++++++++++++--
> kernel/kprobes.c | 99 ++++++++++++++++++++++++-----------
> kernel/trace/trace_output.c | 17 +-----
> lib/error-inject.c | 3 +
> 25 files changed, 200 insertions(+), 105 deletions(-)
>
> --
> Masami Hiramatsu (Linaro) <mhiramat@...nel.org>
--
Masami Hiramatsu <mhiramat@...nel.org>
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