| Message ID | 1444298504-10392-2-git-send-email-takahiro.akashi@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Oct 8, 2015, at 7:01 PM, AKASHI Takahiro wrote: Hi Akashi, > On arm64, no PC values returned by save_stack_trace() will match to LR > values saved in stack frames on a stack after the following commit: > commit e306dfd06fcb ("ARM64: unwind: Fix PC calculation") > As a result, the output from stack tracer will be messed up. > > This patch introduces an arch-defined macro, FTRACE_STACK_FRAME_OFFSET, > so that check_stack() can handle this case correctly. > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> > --- > arch/arm64/include/asm/ftrace.h | 5 +++-- > arch/arm64/kernel/stacktrace.c | 7 ++++--- > include/linux/ftrace.h | 7 +++++++ > kernel/trace/trace_stack.c | 5 +++-- > 4 files changed, 17 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index c5534fa..2b43e20 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -13,8 +13,9 @@ > > #include <asm/insn.h> > > -#define MCOUNT_ADDR ((unsigned long)_mcount) > -#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE > +#define MCOUNT_ADDR ((unsigned long)_mcount) > +#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE > +#define FTRACE_STACK_FRAME_OFFSET AARCH64_INSN_SIZE > > #ifndef __ASSEMBLY__ > #include <linux/compat.h> > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 407991b..bc0689a 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -20,6 +20,7 @@ > #include <linux/sched.h> > #include <linux/stacktrace.h> > > +#include <asm/insn.h> > #include <asm/stacktrace.h> > > /* > @@ -49,10 +50,10 @@ int notrace unwind_frame(struct stackframe *frame) > frame->sp = fp + 0x10; > frame->fp = *(unsigned long *)(fp); > /* > - * -4 here because we care about the PC at time of bl, > - * not where the return will go. > + * decrement PC by AARCH64_INSN_SIZE here because we care about > + * the PC at time of bl, not where the return will go. > */ > - frame->pc = *(unsigned long *)(fp + 8) - 4; > + frame->pc = *(unsigned long *)(fp + 8) - AARCH64_INSN_SIZE; > > return 0; > } > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index 6cd8c0e..d77b195 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -263,6 +263,13 @@ static inline void ftrace_kill(void) { } > #endif /* CONFIG_FUNCTION_TRACER */ > > #ifdef CONFIG_STACK_TRACER > +/* > + * the offset value to add to return address from save_stack_trace() > + */ > +#ifndef FTRACE_STACK_FRAME_OFFSET > +#define FTRACE_STACK_FRAME_OFFSET 0 > +#endif > + > extern int stack_tracer_enabled; > int > stack_trace_sysctl(struct ctl_table *table, int write, > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c > index b746399..30521ea 100644 > --- a/kernel/trace/trace_stack.c > +++ b/kernel/trace/trace_stack.c > @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) > > /* Skip over the overhead of the stack tracer itself */ > for (i = 0; i < max_stack_trace.nr_entries; i++) { > - if (stack_dump_trace[i] == ip) > + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) > break; > } > > @@ -133,7 +133,8 @@ check_stack(unsigned long ip, unsigned long *stack) > for (; p < top && i < max_stack_trace.nr_entries; p++) { > if (stack_dump_trace[i] == ULONG_MAX) > break; > - if (*p == stack_dump_trace[i]) { > + if (*p == (stack_dump_trace[i] > + + FTRACE_STACK_FRAME_OFFSET)) { > stack_dump_trace[x] = stack_dump_trace[i++]; > this_size = stack_dump_index[x++] = > (top - p) * sizeof(unsigned long); > -- This change is always on my tree for IRQ stack feature development. It makes stack_trace prints out useful info although it can't give an accurate data. I believe this hunk helps to figure out max stack depth context. Acked-by: Jungseok Lee <jungseoklee85@gmail.com> Thanks! 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/
On Thu, 8 Oct 2015 19:01:38 +0900 AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > extern int stack_tracer_enabled; > int > stack_trace_sysctl(struct ctl_table *table, int write, > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c > index b746399..30521ea 100644 > --- a/kernel/trace/trace_stack.c > +++ b/kernel/trace/trace_stack.c > @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) > > /* Skip over the overhead of the stack tracer itself */ > for (i = 0; i < max_stack_trace.nr_entries; i++) { > - if (stack_dump_trace[i] == ip) > + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) > break; > } > > @@ -133,7 +133,8 @@ check_stack(unsigned long ip, unsigned long *stack) > for (; p < top && i < max_stack_trace.nr_entries; p++) { > if (stack_dump_trace[i] == ULONG_MAX) > break; > - if (*p == stack_dump_trace[i]) { > + if (*p == (stack_dump_trace[i] > + + FTRACE_STACK_FRAME_OFFSET)) { I'm fine with the patch, but this is one of those cases that I think the 80 column max limit produces uglier code than just going a little over. Or, we can add a helper variable in both locations: addr = stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET; if (*p == addr) { gcc should be smart enough to optimize out the addr variable. -- Steve > stack_dump_trace[x] = stack_dump_trace[i++]; > this_size = stack_dump_index[x++] = > (top - p) * sizeof(unsigned long); -- 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/
On 10/14/2015 12:37 AM, Steven Rostedt wrote: > On Thu, 8 Oct 2015 19:01:38 +0900 > AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > >> extern int stack_tracer_enabled; >> int >> stack_trace_sysctl(struct ctl_table *table, int write, >> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c >> index b746399..30521ea 100644 >> --- a/kernel/trace/trace_stack.c >> +++ b/kernel/trace/trace_stack.c >> @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) >> >> /* Skip over the overhead of the stack tracer itself */ >> for (i = 0; i < max_stack_trace.nr_entries; i++) { >> - if (stack_dump_trace[i] == ip) >> + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) >> break; >> } >> >> @@ -133,7 +133,8 @@ check_stack(unsigned long ip, unsigned long *stack) >> for (; p < top && i < max_stack_trace.nr_entries; p++) { >> if (stack_dump_trace[i] == ULONG_MAX) >> break; >> - if (*p == stack_dump_trace[i]) { >> + if (*p == (stack_dump_trace[i] >> + + FTRACE_STACK_FRAME_OFFSET)) { > > I'm fine with the patch, but this is one of those cases that I think > the 80 column max limit produces uglier code than just going a little > over. > > Or, we can add a helper variable in both locations: > > addr = stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET; > if (*p == addr) { > > gcc should be smart enough to optimize out the addr variable. Thanks, I will take this. (please note that this patch won't be necessary if my patch5,6 and 7 are accepted.) -Takahiro AKASHI > -- Steve > >> stack_dump_trace[x] = stack_dump_trace[i++]; >> this_size = stack_dump_index[x++] = >> (top - p) * sizeof(unsigned long); > -- 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/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h index c5534fa..2b43e20 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h @@ -13,8 +13,9 @@ #include <asm/insn.h> -#define MCOUNT_ADDR ((unsigned long)_mcount) -#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE +#define MCOUNT_ADDR ((unsigned long)_mcount) +#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE +#define FTRACE_STACK_FRAME_OFFSET AARCH64_INSN_SIZE #ifndef __ASSEMBLY__ #include <linux/compat.h> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 407991b..bc0689a 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -20,6 +20,7 @@ #include <linux/sched.h> #include <linux/stacktrace.h> +#include <asm/insn.h> #include <asm/stacktrace.h> /* @@ -49,10 +50,10 @@ int notrace unwind_frame(struct stackframe *frame) frame->sp = fp + 0x10; frame->fp = *(unsigned long *)(fp); /* - * -4 here because we care about the PC at time of bl, - * not where the return will go. + * decrement PC by AARCH64_INSN_SIZE here because we care about + * the PC at time of bl, not where the return will go. */ - frame->pc = *(unsigned long *)(fp + 8) - 4; + frame->pc = *(unsigned long *)(fp + 8) - AARCH64_INSN_SIZE; return 0; } diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 6cd8c0e..d77b195 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -263,6 +263,13 @@ static inline void ftrace_kill(void) { } #endif /* CONFIG_FUNCTION_TRACER */ #ifdef CONFIG_STACK_TRACER +/* + * the offset value to add to return address from save_stack_trace() + */ +#ifndef FTRACE_STACK_FRAME_OFFSET +#define FTRACE_STACK_FRAME_OFFSET 0 +#endif + extern int stack_tracer_enabled; int stack_trace_sysctl(struct ctl_table *table, int write, diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index b746399..30521ea 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) /* Skip over the overhead of the stack tracer itself */ for (i = 0; i < max_stack_trace.nr_entries; i++) { - if (stack_dump_trace[i] == ip) + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) break; } @@ -133,7 +133,8 @@ check_stack(unsigned long ip, unsigned long *stack) for (; p < top && i < max_stack_trace.nr_entries; p++) { if (stack_dump_trace[i] == ULONG_MAX) break; - if (*p == stack_dump_trace[i]) { + if (*p == (stack_dump_trace[i] + + FTRACE_STACK_FRAME_OFFSET)) { stack_dump_trace[x] = stack_dump_trace[i++]; this_size = stack_dump_index[x++] = (top - p) * sizeof(unsigned long);
On arm64, no PC values returned by save_stack_trace() will match to LR values saved in stack frames on a stack after the following commit: commit e306dfd06fcb ("ARM64: unwind: Fix PC calculation") As a result, the output from stack tracer will be messed up. This patch introduces an arch-defined macro, FTRACE_STACK_FRAME_OFFSET, so that check_stack() can handle this case correctly. Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> --- arch/arm64/include/asm/ftrace.h | 5 +++-- arch/arm64/kernel/stacktrace.c | 7 ++++--- include/linux/ftrace.h | 7 +++++++ kernel/trace/trace_stack.c | 5 +++-- 4 files changed, 17 insertions(+), 7 deletions(-)