ARM: 8992/1: Fix unwind_frame for clang-built kernels (b4d5ec9b) · Commits · 戴 / test

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>

arch/arm/kernel/stacktrace.c

+24 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}

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