Messages in this thread | | | From | Sedat Dilek <> | Date | Wed, 17 Jun 2020 06:23:48 +0200 | Subject | Re: [PATCH] Fix unwind_frame for clang-built kernels |
| |
On Wed, Jun 17, 2020 at 12:36 AM 'Nathan Huckleberry' via Clang Built Linux <clang-built-linux@googlegroups.com> wrote: > > Since clang does not push pc and sp in function prologues, the current > implementation of unwind_frame does not work. By using the previous > frame's lr/fp instead of saved pc/sp we get valid unwinds on clang-built > kernels. > > The bounds check on next frame pointer must be changed as well since > there are 8 less bytes between frames. > > This fixes /proc/<pid>/stack. > > Link: https://github.com/ClangBuiltLinux/linux/issues/912 > Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Just a small nit.
Please label your patch with: "arm/stacktrace: ..." or "arm: stacktrace: ..."
git log --oneline arch/arm/kernel/stacktrace.c ...is your friend :-).
- Sedat -
> --- > arch/arm/kernel/stacktrace.c | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c > index cc726afea023..76ea4178a55c 100644 > --- a/arch/arm/kernel/stacktrace.c > +++ b/arch/arm/kernel/stacktrace.c > @@ -22,6 +22,19 @@ > * A simple function epilogue looks like this: > * ldm sp, {fp, sp, pc} > * > + * When compiled with clang, pc and sp are not pushed. A simple function > + * prologue looks like this when built with clang: > + * > + * stmdb {..., fp, lr} > + * add fp, sp, #x > + * sub sp, sp, #y > + * > + * A simple function epilogue looks like this when built with clang: > + * > + * sub sp, fp, #x > + * ldm {..., fp, pc} > + * > + * > * Note that with framepointer enabled, even the leaf functions have the same > * prologue and epilogue, therefore we can ignore the LR value in this case. > */ > @@ -34,6 +47,16 @@ int notrace unwind_frame(struct stackframe *frame) > low = frame->sp; > high = ALIGN(low, THREAD_SIZE); > > +#ifdef CONFIG_CC_IS_CLANG > + /* check current frame pointer is within bounds */ > + if (fp < low + 4 || fp > high - 4) > + return -EINVAL; > + > + frame->sp = frame->fp; > + frame->fp = *(unsigned long *)(fp); > + frame->pc = frame->lr; > + frame->lr = *(unsigned long *)(fp + 4); > +#else > /* check current frame pointer is within bounds */ > if (fp < low + 12 || fp > high - 4) > return -EINVAL; > @@ -42,6 +65,7 @@ int notrace unwind_frame(struct stackframe *frame) > frame->fp = *(unsigned long *)(fp - 12); > frame->sp = *(unsigned long *)(fp - 8); > frame->pc = *(unsigned long *)(fp - 4); > +#endif > > return 0; > } > -- > 2.27.0.290.gba653c62da-goog > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200616223633.73971-1-nhuck%40google.com.
| |