| Message ID | 1438674249-3447-5-git-send-email-takahiro.akashi@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 08/11/2015 11:57 PM, Jungseok Lee wrote: > 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 <takahiro.akashi@linaro.org> >> --- >> 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? You are right. Will fix it if I submit the next version. >> + >> + 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. I don't know Catalin's intention here, but fp always points to saved pair of <fp, lr> and so, in general, "fp + 0x10" is the address of succeeding local variables in callee function. (Remember my acsii art :) This can be the easily-approximated (but not accurate) stack pointer of caller unless we decode function prologues. Thanks, -Takahiro AKASHI > Best Regards > Jungseok Lee > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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); + + return 0; + } + frame->sp = fp + 0x10; frame->fp = *(unsigned long *)(fp); /*
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 <takahiro.akashi@linaro.org> --- arch/arm64/kernel/entry.S | 4 ++++ arch/arm64/kernel/stacktrace.c | 17 +++++++++++++++++ 2 files changed, 21 insertions(+)