Messages in this thread | | | Subject | Re: [BUGFIX PATCH 3/3] kprobes/arm: Fix the return address of multiple kretprobes | From | "Jon Medhurst (Tixy)" <> | Date | Tue, 14 Feb 2017 13:47:07 +0000 |
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On Tue, 2017-02-14 at 10:32 +0000, Jon Medhurst (Tixy) wrote: > On Tue, 2017-02-14 at 00:05 +0900, Masami Hiramatsu wrote: > > This is arm port of commit 737480a0d525 ("kprobes/x86: > > Fix the return address of multiple kretprobes"). > > > > Fix the return address of subsequent kretprobes when multiple > > kretprobes are set on the same function. > > > > For example: > > > > # cd /sys/kernel/debug/tracing > > # echo "r:event1 sys_symlink" > kprobe_events > > # echo "r:event2 sys_symlink" >> kprobe_events > > # echo 1 > events/kprobes/enable > > # ln -s /tmp/foo /tmp/bar > > > > (without this patch) > > > > # cat trace | grep -v ^# > > ln-82 [000] dn.2 68.446525: event1: (kretprobe_trampoline+0x0/0x18 <- SyS_symlink) > > ln-82 [000] dn.2 68.447831: event2: (ret_fast_syscall+0x0/0x1c <- SyS_symlink) > > > > (with this patch) > > > > # cat trace | grep -v ^# > > ln-81 [000] dn.1 39.463469: event1: (ret_fast_syscall+0x0/0x1c <- SyS_symlink) > > ln-81 [000] dn.1 39.464701: event2: (ret_fast_syscall+0x0/0x1c <- SyS_symlink) > > > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > > Cc: KUMANO Syuhei <kumano.prog@gmail.com> > > --- > > I don't fully understand this function, but I've checked that the ARM > version now matches the x86 version (apart from the x86 specific > register fixup and some comments). So, FWIW > > Acked-by: Jon Medhurst <tixy@linaro.org> > > I ran the before and after test case in the commit log on ARM and > verified the result is correct. I also tried running the ARM kprobe > tests with these 3 fixes but the tests fail. However, they also fail > without any of these changes, so I'll investigate that further...
Bisecting the issue led me back to Linux 4.5 and commit 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
This sets CONFIG_DEBUG_RODATA to be enabled by default. If I disable that on 4.10-rc4, with the three patches in this series, then the ARM kprobes tests pass OK.
I'll stick the DEBUG_RODATA issue on my todo list (it's been around for a year, so can probably wait a little longer).
-- Tixy
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