From: Nathan Huckleberry nhuck@google.com
commit b4d5ec9b39f8b31d98f65bc5577b5d15d93795d7 upstream.
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
Reported-by: Miles Chen miles.chen@mediatek.com Tested-by: Miles Chen miles.chen@mediatek.com Cc: stable@vger.kernel.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Nathan Huckleberry nhuck@google.com Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm/kernel/stacktrace.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
--- a/arch/arm/kernel/stacktrace.c +++ b/arch/arm/kernel/stacktrace.c @@ -20,6 +20,19 @@ * 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. */ @@ -32,6 +45,16 @@ int notrace unwind_frame(struct stackfra 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; @@ -40,6 +63,7 @@ int notrace unwind_frame(struct stackfra frame->fp = *(unsigned long *)(fp - 12); frame->sp = *(unsigned long *)(fp - 8); frame->pc = *(unsigned long *)(fp - 4); +#endif
return 0; }