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 <m...@chromium.org>
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
---
tools/objtool/check.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 92b6a2c21631..f02df714c18e 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 */
--
2.14.3
