From 3c1f05835cbf9fdfe60b81c718d82ceb94b6c55e Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Thu, 22 Mar 2018 13:00:37 -0500 Subject: [PATCH 1/2] objtool: Add Clang support Since the ORC unwinder was made the default on x86_64, Clang-built defconfig kernels have triggered some new objtool warnings: drivers/gpu/drm/i915/i915_gpu_error.o: warning: objtool: i915_error_printf()+0x6c: return with modified stack frame drivers/gpu/drm/i915/intel_display.o: warning: objtool: pipe_config_err()+0xa6: return with modified stack frame The problem is that objtool has never seen clang-built binaries before. Shockingly enough, objtool is apparently able to follow the code flow mostly fine, except for one instruction sequence. Instead of a LEAVE instruction, clang restores RSP and RBP the long way: 67c: 48 89 ec mov %rbp,%rsp 67f: 5d pop %rbp Teach objtool about this new code sequence. Reported-and-test-by: Matthias Kaehlcke Signed-off-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Matthias Kaehlcke Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/fce88ce81c356eedcae7f00ed349cfaddb3363cc.1521741586.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- tools/objtool/check.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 92b6a2c21631d8..5409f6f6c48d63 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1386,6 +1386,17 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state) state->vals[op->dest.reg].offset = -state->stack_size; } + else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && + cfa->base == CFI_BP) { + + /* + * mov %rbp, %rsp + * + * Restore the original stack pointer (Clang). + */ + state->stack_size = -state->regs[CFI_BP].offset; + } + else if (op->dest.reg == cfa->base) { /* mov %reg, %rsp */ From bd6271039ee6f0c9b468148fc2d73e0584af6b4f Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Sun, 14 Jan 2018 15:05:04 +0300 Subject: [PATCH 2/2] x86/alternatives: Fixup alternative_call_2 The following pattern fails to compile while the same pattern with alternative_call() does: if (...) alternative_call_2(...); else alternative_call_2(...); as it expands into if (...) { }; <=== else { }; Signed-off-by: Alexey Dobriyan Signed-off-by: Thomas Gleixner Acked-by: Borislav Petkov Link: https://lkml.kernel.org/r/20180114120504.GA11368@avx2 --- arch/x86/include/asm/alternative.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index cf5961ca867746..4cd6a3b7182429 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -218,13 +218,11 @@ static inline int alternatives_text_reserved(void *start, void *end) */ #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ output, input...) \ -{ \ asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ "call %P[new2]", feature2) \ : output, ASM_CALL_CONSTRAINT \ : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ - [new2] "i" (newfunc2), ## input); \ -} + [new2] "i" (newfunc2), ## input) /* * use this macro(s) if you need more than one output parameter