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Subject[RFC PATCH -tip 0/3] x86/kprobes,orc: Fix ORC unwinder to unwind stack with optimized probe
Date
Hello,

These patches fixes the ORC unwinder to unwind optprobe trampoline
code on the stack correctly.
This patchset is based on the kretporbe and stacktrace fix series v5
which I sent last week.

https://lore.kernel.org/bpf/161676170650.330141.6214727134265514123.stgit@devnote2/

Note that I just confirmed the it fixes the case where the
stacktrace called from the optprobe handler. So this should be
carefully reviewed.


Here is the test code;

cd /sys/kernel/debug/tracing
echo > trace
echo p full_proxy_read+5 >> kprobe_events
echo 1 > events/kprobes/enable
sleep 1 # wait for optimization
echo stacktrace:1 > events/kprobes/p_full_proxy_read_5/trigger
echo 1 > options/sym-offset
cat /sys/kernel/debug/kprobes/list


Without this,

cat-138 [001] ...1 6.567662: p_full_proxy_read_5: (full_proxy_read+0x5/0x80)
cat-138 [001] ...1 6.567711: <stack trace>
=> kprobe_trace_func+0x1d0/0x2c0
=> kprobe_dispatcher+0x39/0x60
=> opt_pre_handler+0x4f/0x80
=> optimized_callback+0xc3/0xf0
=> 0xffffffffa0006032
=> 0
=> 0


With this patch,

cat-137 [007] ...1 17.542848: p_full_proxy_read_5: (full_proxy_read+0x5/0x80)
cat-137 [007] ...1 17.542963: <stack trace>
=> kprobe_trace_func+0x1d0/0x2c0
=> kprobe_dispatcher+0x39/0x60
=> opt_pre_handler+0x4f/0x80
=> optimized_callback+0xc3/0xf0
=> full_proxy_read+0x5/0x80
=> vfs_read+0xab/0x1a0
=> ksys_read+0x5f/0xe0
=> do_syscall_64+0x33/0x40
=> entry_SYSCALL_64_after_hwframe+0x44/0xae
=> 0
=> 0


Thank you,

---

Masami Hiramatsu (3):
x86/kprobes: Add ORC information to optprobe template
kprobes: Add functions to find instruction buffer entry address
x86/kprobes,orc: Unwind optprobe trampoline correctly


arch/x86/include/asm/kprobes.h | 6 +++
arch/x86/kernel/kprobes/opt.c | 72 +++++++++++++++++++++++++++++++++++++---
arch/x86/kernel/unwind_orc.c | 15 +++++++-
include/linux/kprobes.h | 8 ++++
kernel/kprobes.c | 25 ++++++++++----
5 files changed, 111 insertions(+), 15 deletions(-)

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

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