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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 <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.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2018-03-22 13:00:37 -05:00 committed by Ingo Molnar
parent d8ba61ba58
commit 3c1f05835c
1 changed files with 11 additions and 0 deletions
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11
tools/objtool/check.c
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@ -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 */