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

Masami Hiramatsu
2021-07-11T13:34:40Z

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) <mhiramat@kernel.org>