4.14-stable review patch. If anyone has any objections, please let me know.
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From: Josh Poimboeuf jpoimboe@redhat.com
commit 3c1f05835cbf9fdfe60b81c718d82ceb94b6c55e upstream.
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 mka@chromium.org Signed-off-by: Josh Poimboeuf jpoimboe@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matthias Kaehlcke mka@chromium.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/fce88ce81c356eedcae7f00ed349cfaddb3363cc.1521741586... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- tools/objtool/check.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
--- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1385,6 +1385,17 @@ static int update_insn_state(struct inst 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 */