On Aug 4, 2015, at 4:44 PM, AKASHI Takahiro wrote: Hi Akashi,
> On arm64, an exception handler use the same stack as in non-exception > contexts, but doesn't create a stack frame for elx_xx entry, only updating > sp register. This behavior results in save_stace_trace() missing a function > that is the one when an exception happens. > > This patch creates a stack frame for this case, and puts an additional > entry for the function in a stack trace list. > > Signed-off-by: AKASHI Takahiro <[email protected]> > --- > arch/arm64/kernel/entry.S | 4 ++++ > arch/arm64/kernel/stacktrace.c | 17 +++++++++++++++++ > 2 files changed, 21 insertions(+) > > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index f860bfd..aacb6c6 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -107,6 +107,8 @@ > str x21, [sp, #S_SYSCALLNO] > .endif > > + /* create a stack frame for stack tracer */ > + mov x29, sp > /* > * Registers that may be useful after this macro is invoked: > * > @@ -737,3 +739,5 @@ ENTRY(sys_rt_sigreturn_wrapper) > mov x0, sp > b sys_rt_sigreturn > ENDPROC(sys_rt_sigreturn_wrapper) > + > +ENTRY(end_of_vectors) > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index d1790eb..22ce7c9 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -25,6 +25,10 @@ > #include <asm/stacktrace.h> > > #define S_FRAME_SIZE sizeof(struct pt_regs) /* asm-offsets.h */ > +#define S_FP offsetof(struct pt_regs, regs[29]) > +#define S_LR offsetof(struct pt_regs, regs[30]) > + > +extern unsigned int *vectors, *end_of_vectors; > > /* > * AArch64 PCS assigns the frame pointer to x29. > @@ -50,6 +54,19 @@ int notrace unwind_frame(struct stackframe *frame) > if (fp < low || fp > high - 0x18 || fp & 0xf) > return -EINVAL; > > + if ((frame->pc >= (unsigned long)&vectors) && > + (frame->pc < (unsigned long)&end_of_vectors)) { > + /* > + * Expection handler does not use a normal format of > + * stack frame, but allocates struct pt_regs. > + */ > + frame->sp = frame->sp + S_FRAME_SIZE; > + frame->fp = *(unsigned long *)(fp + S_FP); > + frame->pc = *(unsigned long *)(fp + S_LR); Not frame->pc = *(unsigned long *)(fp + S_PC)? Don't we need to look up elr_el1 since this is an exception? > + > + return 0; > + } > + > frame->sp = fp + 0x10; I'm just curious about this constant, 0x10. Do you have an idea on this value? As reviewing objdump of vmlinux, it looks needed to analyze the first store-pair instruction of each function. Please correct me if I'm wrong. Best Regards Jungseok Lee-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
