This is a note to let you know that I've just added the patch titled
arm64: ftrace: fix function_graph tracer panic
to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-ftrace-fix-function_graph-tracer-panic.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ee556d00cf20012e889344a0adbbf809ab5015a3 Mon Sep 17 00:00:00 2001
From: Li Bin <huawei.libin@xxxxxxxxxx>
Date: Wed, 30 Sep 2015 10:49:55 +0800
Subject: arm64: ftrace: fix function_graph tracer panic
From: Li Bin <huawei.libin@xxxxxxxxxx>
commit ee556d00cf20012e889344a0adbbf809ab5015a3 upstream.
When function graph tracer is enabled, the following operation
will trigger panic:
mount -t debugfs nodev /sys/kernel
echo next_tgid > /sys/kernel/tracing/set_ftrace_filter
echo function_graph > /sys/kernel/tracing/current_tracer
ls /proc/
------------[ cut here ]------------
[ 198.501417] Unable to handle kernel paging request at virtual address cb88537fdc8ba316
[ 198.506126] pgd = ffffffc008f79000
[ 198.509363] [cb88537fdc8ba316] *pgd=00000000488c6003, *pud=00000000488c6003, *pmd=0000000000000000
[ 198.517726] Internal error: Oops: 94000005 [#1] SMP
[ 198.518798] Modules linked in:
[ 198.520582] CPU: 1 PID: 1388 Comm: ls Tainted: G
[ 198.521800] Hardware name: linux,dummy-virt (DT)
[ 198.522852] task: ffffffc0fa9e8000 ti: ffffffc0f9ab0000 task.ti: ffffffc0f9ab0000
[ 198.524306] PC is at next_tgid+0x30/0x100
[ 198.525205] LR is at return_to_handler+0x0/0x20
[ 198.526090] pc : [<ffffffc0002a1070>] lr : [<ffffffc0000907c0>] pstate: 60000145
[ 198.527392] sp : ffffffc0f9ab3d40
[ 198.528084] x29: ffffffc0f9ab3d40 x28: ffffffc0f9ab0000
[ 198.529406] x27: ffffffc000d6a000 x26: ffffffc000b786e8
[ 198.530659] x25: ffffffc0002a1900 x24: ffffffc0faf16c00
[ 198.531942] x23: ffffffc0f9ab3ea0 x22: 0000000000000002
[ 198.533202] x21: ffffffc000d85050 x20: 0000000000000002
[ 198.534446] x19: 0000000000000002 x18: 0000000000000000
[ 198.535719] x17: 000000000049fa08 x16: ffffffc000242efc
[ 198.537030] x15: 0000007fa472b54c x14: ffffffffff000000
[ 198.538347] x13: ffffffc0fada84a0 x12: 0000000000000001
[ 198.539634] x11: ffffffc0f9ab3d70 x10: ffffffc0f9ab3d70
[ 198.540915] x9 : ffffffc0000907c0 x8 : ffffffc0f9ab3d40
[ 198.542215] x7 : 0000002e330f08f0 x6 : 0000000000000015
[ 198.543508] x5 : 0000000000000f08 x4 : ffffffc0f9835ec0
[ 198.544792] x3 : cb88537fdc8ba316 x2 : cb88537fdc8ba306
[ 198.546108] x1 : 0000000000000002 x0 : ffffffc000d85050
[ 198.547432]
[ 198.547920] Process ls (pid: 1388, stack limit = 0xffffffc0f9ab0020)
[ 198.549170] Stack: (0xffffffc0f9ab3d40 to 0xffffffc0f9ab4000)
[ 198.582568] Call trace:
[ 198.583313] [<ffffffc0002a1070>] next_tgid+0x30/0x100
[ 198.584359] [<ffffffc0000907bc>] ftrace_graph_caller+0x6c/0x70
[ 198.585503] [<ffffffc0000907bc>] ftrace_graph_caller+0x6c/0x70
[ 198.586574] [<ffffffc0000907bc>] ftrace_graph_caller+0x6c/0x70
[ 198.587660] [<ffffffc0000907bc>] ftrace_graph_caller+0x6c/0x70
[ 198.588896] Code: aa0003f5 2a0103f4 b4000102 91004043 (885f7c60)
[ 198.591092] ---[ end trace 6a346f8f20949ac8 ]---
This is because when using function graph tracer, if the traced
function return value is in multi regs ([x0-x7]), return_to_handler
may corrupt them. So in return_to_handler, the parameter regs should
be protected properly.
Signed-off-by: Li Bin <huawei.libin@xxxxxxxxxx>
Acked-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/entry-ftrace.S | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -178,6 +178,24 @@ ENTRY(ftrace_stub)
ENDPROC(ftrace_stub)
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ /* save return value regs*/
+ .macro save_return_regs
+ sub sp, sp, #64
+ stp x0, x1, [sp]
+ stp x2, x3, [sp, #16]
+ stp x4, x5, [sp, #32]
+ stp x6, x7, [sp, #48]
+ .endm
+
+ /* restore return value regs*/
+ .macro restore_return_regs
+ ldp x0, x1, [sp]
+ ldp x2, x3, [sp, #16]
+ ldp x4, x5, [sp, #32]
+ ldp x6, x7, [sp, #48]
+ add sp, sp, #64
+ .endm
+
/*
* void ftrace_graph_caller(void)
*
@@ -204,11 +222,11 @@ ENDPROC(ftrace_graph_caller)
* only when CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST is enabled.
*/
ENTRY(return_to_handler)
- str x0, [sp, #-16]!
+ save_return_regs
mov x0, x29 // parent's fp
bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
mov x30, x0 // restore the original return address
- ldr x0, [sp], #16
+ restore_return_regs
ret
END(return_to_handler)
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
Patches currently in stable-queue which might be from huawei.libin@xxxxxxxxxx are
queue-4.2/arm64-ftrace-fix-function_graph-tracer-panic.patch
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