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Date: Thu, 20 Aug 2020 11:22:19 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Miles Chen <miles.chen@...iatek.com>, Nick Desaulniers <ndesaulniers@...gle.com>, Nathan Huckleberry <nhuck@...gle.com>, Russell King <rmk+kernel@...linux.org.uk> Subject: [PATCH 4.9 166/212] ARM: 8992/1: Fix unwind_frame for clang-built kernels From: Nathan Huckleberry <nhuck@...gle.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@...iatek.com> Tested-by: Miles Chen <miles.chen@...iatek.com> Cc: stable@...r.kernel.org Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com> Signed-off-by: Nathan Huckleberry <nhuck@...gle.com> Signed-off-by: Russell King <rmk+kernel@...linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/arm/kernel/stacktrace.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) --- a/arch/arm/kernel/stacktrace.c +++ b/arch/arm/kernel/stacktrace.c @@ -19,6 +19,19 @@ * 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. */ @@ -31,6 +44,16 @@ 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; @@ -39,6 +62,7 @@ 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; }
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