[PATCH -tip 0/4][BUGFIX] Fix ftrace-based kprobes

Masami Hiramatsu
2012-09-05T14:32:20Z

Hi,

This series of patches fixes some bugs and corrects behaviors
of ftrace and ftrace-based kprobe.

As Fengguang reported at https://lkml.org/lkml/2012/8/24/45
ftrace-based kprobes and -mfentry option caused failures
on kprobe smoke test. This basically comes from the initial
design of ftrace-based kprobe which prohibits jprobe on
ftraced kprobe.
Without -mfentry support, this works well because NO mcount
call is at the first instruction of any function. However,
-mfentry calls it at the first one and it conflicts with
jprobe.

On this series, kprobe allows jprobe even if it is based on
ftrace. For this fix, I need following fixes.

- Make ftrace-handler interface same on x86/x86-64
On x86, ftrace_regs_caller puts a same address on ip and
regs.ip, however those are different on x86-64. I've
modified x86 to fit to x86-64 ABI.
- Fix kprobe ftrace handler for above ABI change
Current kprobe_ftrace_handler expects ip == regs.ip, but
it's not correct on x86-64 (and now on x86 too). This should
be fixed.
- Use regs.ip for return address on ftrace
From Steven, this change is suggested. Thanks!

Thank you,

---

Masami Hiramatsu (3):
[BUGFIX] kprobes/x86: Fix to support jprobes on ftrace-based kprobe
[BUGFIX] kprobes/x86: Fix kprobes to collectly handle IP on ftrace
[BUGFIX] ftrace/x86: Adjust x86 regs.ip as like as x86-64

Steven Rostedt (1):
ftrace/x86-64: Allow to change RIP in handlers

arch/x86/kernel/entry_32.S | 3 +--
arch/x86/kernel/entry_64.S | 4 ++++
arch/x86/kernel/kprobes.c | 43 +++++++++++++++++++++++++++++++------------
kernel/kprobes.c | 3 ---
4 files changed, 36 insertions(+), 17 deletions(-)

--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com