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

[Masami Hiramatsu <mhiramat@kernel.org>]

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>