Messages in this thread | | | Subject | Re: [PATCH] arm64: ftrace: fix function_graph tracer panic | From | AKASHI Takahiro <> | Date | Thu, 1 Oct 2015 15:11:29 +0900 |
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On 09/30/2015 11:49 AM, Li Bin wrote: > 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 ([0x-07]), return_to_handler > may corrupt them. So in return_to_handler, the parameter regs should > be protected properly.
You're right. we should preserve x0-x7 around a call to ftrace_return_to_handler() just in case they might be used as a "composite type" (ie. struct) of return value.
Thanks, -Takahiro AKASHI
> Cc: <stable@vger.kernel.org> # 3.18+ > Signed-off-by: Li Bin <huawei.libin@huawei.com> > --- > arch/arm64/kernel/entry-ftrace.S | 22 ++++++++++++++++++++-- > 1 files changed, 20 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S > index 08cafc5..0f03a8f 100644 > --- 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 */ >
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