Commit 3c1f0583 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

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: default avatarMatthias Kaehlcke <mka@chromium.org>
Signed-off-by: default avatarJosh 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.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d8ba61ba

tools/objtool/check.c

+11 −0
Original line number Diff line number Diff line
@@ -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 */

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