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| author | Petri Gynther | 2014-07-24 07:55:02 +0200 |
|---|---|---|
| committer | Ralf Baechle | 2014-07-30 20:37:42 +0200 |
| commit | dce0e7d54a710400c0056d86d0f0ed972133b25d (patch) | |
| tree | 09c4e4a9ff99b1d11150e62c21f519264513254c /arch/mips/kernel/mcount.S | |
| parent | MIPS: Prevent user from setting FCSR cause bits (diff) | |
| download | kernel-qcow2-linux-dce0e7d54a710400c0056d86d0f0ed972133b25d.tar.gz kernel-qcow2-linux-dce0e7d54a710400c0056d86d0f0ed972133b25d.tar.xz kernel-qcow2-linux-dce0e7d54a710400c0056d86d0f0ed972133b25d.zip | |
MIPS: ftrace: Fix dynamic tracing of kernel modules
Dynamic tracing of kernel modules is broken on 32-bit MIPS. When modules
are loaded, the kernel crashes when dynamic tracing is enabled with:
cd /sys/kernel/debug/tracing
echo > set_ftrace_filter
echo function > current_tracer
1) arch/mips/kernel/ftrace.c
When the kernel boots, or when a module is initialized, ftrace_make_nop()
modifies every _mcount call site to eliminate the ftrace overhead.
However, when ftrace is later enabled for a call site, ftrace_make_call()
does not currently restore the _mcount call correctly for module call sites.
Added ftrace_modify_code_2r() and modified ftrace_make_call() to fix this.
2) arch/mips/kernel/mcount.S
_mcount assembly routine is supposed to have the caller's _mcount call site
address in register a0. However, a0 is currently not calculated correctly for
module call sites. a0 should be (ra - 20) or (ra - 24), depending on whether
the kernel was built with KBUILD_MCOUNT_RA_ADDRESS or not.
This fix has been tested on Broadcom BMIPS5000 processor. Dynamic tracing
now works for both built-in functions and module functions.
Signed-off-by: Petri Gynther <pgynther@google.com>
Cc: linux-mips@linux-mips.org
Cc: rostedt@goodmis.org
Cc: alcooperx@gmail.com
Cc: cminyard@mvista.com
Patchwork: https://patchwork.linux-mips.org/patch/7476/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/kernel/mcount.S')
| -rw-r--r-- | arch/mips/kernel/mcount.S | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S index 539b6294b613..26ceb3c0eca9 100644 --- a/arch/mips/kernel/mcount.S +++ b/arch/mips/kernel/mcount.S @@ -84,6 +84,19 @@ _mcount: #endif PTR_SUBU a0, ra, 8 /* arg1: self address */ + PTR_LA t1, _stext + sltu t2, a0, t1 /* t2 = (a0 < _stext) */ + PTR_LA t1, _etext + sltu t3, t1, a0 /* t3 = (a0 > _etext) */ + or t1, t2, t3 + beqz t1, ftrace_call + nop +#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT) + PTR_SUBU a0, a0, 16 /* arg1: adjust to module's recorded callsite */ +#else + PTR_SUBU a0, a0, 12 +#endif + .globl ftrace_call ftrace_call: nop /* a placeholder for the call to a real tracing function */ |