[PATCH -tip v11 00/27] kprobes: Fix stacktrace with kretprobes on x86

Masami Hiramatsu
2021-09-14T14:38:27Z

Hello,

This is the 11th version of the series to fix the stacktrace with kretprobe on x86.

The previous version is here;

https://lore.kernel.org/all/162756755600.301564.4957591913842010341.stgit@devnote2/

This version is rebased on the latest tip/master branch and includes the kprobe cleanup
series[1][2]. No code change.

[1] https://lore.kernel.org/bpf/162748615977.59465.13262421617578791515.stgit@devnote2/
[2] https://lore.kernel.org/linux-csky/20210727133426.2919710-1-punitagrawal@gmail.com/

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
ffffffff813bedf0 r full_proxy_read+0x0 [FTRACE]
ffffffff812c13e0 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
# ||| / _-=> migrate-disable
# |||| / delay
# TASK-PID CPU# ||||| TIMESTAMP FUNCTION
# | | | ||||| | |
cat-136 [000] ...1. 14.474966: r_full_proxy_read_0: (vfs_read+0x99/0x190 <- full_proxy_read)
cat-136 [000] ...1. 14.474970: <stack trace>
=> kretprobe_trace_func+0x209/0x300
=> kretprobe_dispatcher+0x9d/0xb0
=> __kretprobe_trampoline_handler+0xd4/0x1b0
=> trampoline_handler+0x43/0x60
=> __kretprobe_trampoline+0x2a/0x50
=> vfs_read+0x99/0x190
=> ksys_read+0x68/0xe0
=> do_syscall_64+0x3b/0x90
=> entry_SYSCALL_64_after_hwframe+0x44/0xae
cat-136 [000] ...1. 14.474971: r_vfs_read_0: (ksys_read+0x68/0xe0 <- 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+0x68' and full_proxy_read()
returns to 'vfs_read+0x99')

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-v11

Thank you,

---

Josh Poimboeuf (3):
objtool: Add frame-pointer-specific function ignore
objtool: Ignore unwind hints for ignored functions
x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline()

Masami Hiramatsu (19):
kprobes: treewide: Cleanup the error messages for kprobes
kprobes: Fix coding style issues
kprobes: Use IS_ENABLED() instead of kprobes_built_in()
kprobes: Add assertions for required lock
kprobes: treewide: Use 'kprobe_opcode_t *' for the code address in get_optimized_kprobe()
kprobes: Use bool type for functions which returns boolean value
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

Punit Agrawal (5):
kprobes: Do not use local variable when creating debugfs file
kprobes: Use helper to parse boolean input from userspace
kprobe: Simplify prepare_kprobe() by dropping redundant version
csky: ftrace: Drop duplicate implementation of arch_check_ftrace_location()
kprobes: Make arch_check_ftrace_location static

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 | 15 -
arch/arm/probes/kprobes/opt-arm.c | 7
arch/arm64/include/asm/kprobes.h | 2
arch/arm64/kernel/probes/kprobes.c | 10
arch/arm64/kernel/probes/kprobes_trampoline.S | 4
arch/csky/include/asm/kprobes.h | 2
arch/csky/kernel/probes/ftrace.c | 7
arch/csky/kernel/probes/kprobes.c | 14 -
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 | 26 +
arch/parisc/kernel/kprobes.c | 6
arch/powerpc/include/asm/kprobes.h | 2
arch/powerpc/kernel/kprobes.c | 29 -
arch/powerpc/kernel/optprobes.c | 8
arch/powerpc/kernel/stacktrace.c | 2
arch/riscv/include/asm/kprobes.h | 2
arch/riscv/kernel/probes/kprobes.c | 15 -
arch/riscv/kernel/probes/kprobes_trampoline.S | 4
arch/s390/include/asm/kprobes.h | 2
arch/s390/kernel/kprobes.c | 16 -
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/kprobes/opt.c | 6
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 | 113 ++++--
include/linux/objtool.h | 12 +
kernel/kprobes.c | 502 ++++++++++++++-----------
kernel/trace/trace_kprobe.c | 2
kernel/trace/trace_output.c | 17 -
lib/error-inject.c | 3
tools/include/linux/objtool.h | 12 +
tools/objtool/check.c | 2
46 files changed, 607 insertions(+), 436 deletions(-)

--
Masami Hiramatsu (Linaro) <mhiramat@kernel.org>