Message-Id: <161639518354.895304.15627519393073806809.stgit@devnote2>
Date:   Mon, 22 Mar 2021 15:39:43 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     X86 ML <x86@...nel.org>, Masami Hiramatsu <mhiramat@...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,
        Abhishek Sagar <sagar.abhishek@...il.com>
Subject: [PATCH -tip v4 00/12] kprobes: Fix stacktrace with kretprobes on x86

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>

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