[-tip,v4,00/12] kprobes: Fix stacktrace with kretprobes on x86

Message

Masami Hiramatsu (Google) March 22, 2021, 6:39 a.m. UTC

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) <[e-mail]>