[-tip,v9,00/14] kprobes: Fix stacktrace with kretprobes on x86

Message

Masami Hiramatsu (Google) July 11, 2021, 1:34 p.m. UTC

Hello,

This is the 9th version of the series to fix the stacktrace with kretprobe on x86.

The previous version is;

 https://lore.kernel.org/bpf/162399992186.506599.8457763707951687195.stgit@devnote2/

This version is mostly cleaning up changelogs, comments, and coding styles
accoding to Ingo's comment. This series also depends on my kprobe cleanup
series (*1) and Josh's objtool update series (*2)(*3)

(*1) https://lore.kernel.org/bpf/162598881438.1222130.11530594038964049135.stgit@devnote2/
(*2) https://lore.kernel.org/bpf/20210710192433.x5cgjsq2ksvaqnss@treble/
(*3) https://lore.kernel.org/bpf/20210710192514.ghvksi3ozhez4lvb@treble/

Changes from v8:
 [1/14]
      - Update changelog and add stable to Cc.
 [2/14]
      - Update changelog.
 [3/14]
      - Update changelog.
 [4/14]
      - Newly added accoding to Ingo's suggestion.
 [5/14]
      - Update changelog and comments.
      - Consolidate the prototypes in the header file.
      - Make __kretprobe_find_ret_addr() return 'kprobe_opcode_t *'.
 [6/14]
      - Update changelog and comments.
      - Use STACK_FRAME_NON_STANDARD_FP().
 [8/14]
      - Fix "space at the start of a line" checkpatch warnings.
 [9/14]
      - Update changelog.
 [10/14]
      - Update comments to explain why this is needed.
 [11/14]
      - Update changelog and comments.
      - Remove unneeded type casting.
 [12/14]
      - Update comments.
 [14/14]
      - Fix the changelog and add more comments.

All over this series, I fixed my typo on Andrii's name (I'm sorry).


With this series, unwinder can unwind stack correctly from ftrace as below;

  # cd /sys/kernel/debug/tracing
  # echo > trace
  # echo 1 > options/sym-offset
  # 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
  # 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
#              | |         |   ||||      |         |
           <...>-134     [007] ...1    16.185877: r_full_proxy_read_0: (vfs_read+0x98/0x180 <- full_proxy_read)
           <...>-134     [007] ...1    16.185901: <stack trace>
 => kretprobe_trace_func+0x209/0x300
 => kretprobe_dispatcher+0x4a/0x70
 => __kretprobe_trampoline_handler+0xd4/0x170
 => trampoline_handler+0x43/0x60
 => kretprobe_trampoline+0x2a/0x50
 => vfs_read+0x98/0x180
 => ksys_read+0x5f/0xe0
 => do_syscall_64+0x37/0x90
 => entry_SYSCALL_64_after_hwframe+0x44/0xae
           <...>-134     [007] ...1    16.185902: r_vfs_read_0: (ksys_read+0x5f/0xe0 <- vfs_read)

This shows the double return probes (vfs_read() and full_proxy_read()) on the stack
correctly unwinded. (vfs_read() returns to 'ksys_read+0x5f' and full_proxy_read()
returns to 'vfs_read+0x98')

This also 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, and can use
stack_trace_save_regs().

You can also get this series from 
 git://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/kretprobe-stackfix-v9


Thank you,

---

Josh Poimboeuf (1):
      x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline()

Masami Hiramatsu (13):
      ia64: kprobes: Fix to pass correct trampoline address to the handler
      kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_descriptor()
      kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler()
      kprobes: treewide: Make it harder to refer kretprobe_trampoline directly
      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 space for instruction pointer on stack
      kprobes: Enable stacktrace from pt_regs in kretprobe 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
      x86/kprobes: Fixup return address in generic trampoline handler


 arch/arc/include/asm/kprobes.h                |    2 
 arch/arc/include/asm/ptrace.h                 |    5 +
 arch/arc/kernel/kprobes.c                     |   13 ++-
 arch/arm/probes/kprobes/core.c                |   11 +-
 arch/arm64/include/asm/kprobes.h              |    2 
 arch/arm64/kernel/probes/kprobes.c            |    5 -
 arch/arm64/kernel/probes/kprobes_trampoline.S |    4 -
 arch/csky/include/asm/kprobes.h               |    2 
 arch/csky/kernel/probes/kprobes.c             |    4 -
 arch/csky/kernel/probes/kprobes_trampoline.S  |    4 -
 arch/ia64/include/asm/ptrace.h                |    5 +
 arch/ia64/kernel/kprobes.c                    |   15 +--
 arch/mips/kernel/kprobes.c                    |   15 ++-
 arch/parisc/kernel/kprobes.c                  |    6 +
 arch/powerpc/include/asm/kprobes.h            |    2 
 arch/powerpc/kernel/kprobes.c                 |   29 ++----
 arch/powerpc/kernel/optprobes.c               |    2 
 arch/powerpc/kernel/stacktrace.c              |    2 
 arch/riscv/include/asm/kprobes.h              |    2 
 arch/riscv/kernel/probes/kprobes.c            |    4 -
 arch/riscv/kernel/probes/kprobes_trampoline.S |    4 -
 arch/s390/include/asm/kprobes.h               |    2 
 arch/s390/kernel/kprobes.c                    |   12 +--
 arch/s390/kernel/stacktrace.c                 |    2 
 arch/sh/include/asm/kprobes.h                 |    2 
 arch/sh/kernel/kprobes.c                      |   12 +--
 arch/sparc/include/asm/kprobes.h              |    2 
 arch/sparc/kernel/kprobes.c                   |   12 +--
 arch/x86/include/asm/kprobes.h                |    1 
 arch/x86/include/asm/unwind.h                 |   23 +++++
 arch/x86/include/asm/unwind_hints.h           |    5 +
 arch/x86/kernel/kprobes/core.c                |   71 ++++++++++++---
 arch/x86/kernel/unwind_frame.c                |    3 -
 arch/x86/kernel/unwind_guess.c                |    3 -
 arch/x86/kernel/unwind_orc.c                  |   21 ++++-
 include/linux/kprobes.h                       |   44 ++++++++--
 kernel/kprobes.c                              |  115 ++++++++++++++++++-------
 kernel/trace/trace_output.c                   |   17 +---
 lib/error-inject.c                            |    3 -
 39 files changed, 317 insertions(+), 171 deletions(-)

--
Masami Hiramatsu (Linaro) <[e-mail]>