releases/4.14.34/objtool-add-clang-support.patch

   1 From 3c1f05835cbf9fdfe60b81c718d82ceb94b6c55e Mon Sep 17 00:00:00 2001
   2 From: Josh Poimboeuf <jpoimboe@redhat.com>
   3 Date: Thu, 22 Mar 2018 13:00:37 -0500
   4 Subject: objtool: Add Clang support
   5
   6 From: Josh Poimboeuf <jpoimboe@redhat.com>
   7
   8 commit 3c1f05835cbf9fdfe60b81c718d82ceb94b6c55e upstream.
   9
  10 Since the ORC unwinder was made the default on x86_64, Clang-built
  11 defconfig kernels have triggered some new objtool warnings:
  12
  13   drivers/gpu/drm/i915/i915_gpu_error.o: warning: objtool: i915_error_printf()+0x6c: return with modified stack frame
  14   drivers/gpu/drm/i915/intel_display.o: warning: objtool: pipe_config_err()+0xa6: return with modified stack frame
  15
  16 The problem is that objtool has never seen clang-built binaries before.
  17
  18 Shockingly enough, objtool is apparently able to follow the code flow
  19 mostly fine, except for one instruction sequence.  Instead of a LEAVE
  20 instruction, clang restores RSP and RBP the long way:
  21
  22    67c:   48 89 ec                mov    %rbp,%rsp
  23    67f:   5d                      pop    %rbp
  24
  25 Teach objtool about this new code sequence.
  26
  27 Reported-and-test-by: Matthias Kaehlcke <mka@chromium.org>
  28 Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
  29 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  30 Cc: Matthias Kaehlcke <mka@chromium.org>
  31 Cc: Peter Zijlstra <peterz@infradead.org>
  32 Cc: Thomas Gleixner <tglx@linutronix.de>
  33 Link: http://lkml.kernel.org/r/fce88ce81c356eedcae7f00ed349cfaddb3363cc.1521741586.git.jpoimboe@redhat.com
  34 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  35 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  36
  37 ---
  38  tools/objtool/check.c |   11 +++++++++++
  39  1 file changed, 11 insertions(+)
  40
  41 --- a/tools/objtool/check.c
  42 +++ b/tools/objtool/check.c
  43 @@ -1385,6 +1385,17 @@ static int update_insn_state(struct inst
  44                                 state->vals[op->dest.reg].offset = -state->stack_size;
  45                         }
  46
  47 +                       else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
  48 +                                cfa->base == CFI_BP) {
  49 +
  50 +                               /*
  51 +                                * mov %rbp, %rsp
  52 +                                *
  53 +                                * Restore the original stack pointer (Clang).
  54 +                                */
  55 +                               state->stack_size = -state->regs[CFI_BP].offset;
  56 +                       }
  57 +
  58                         else if (op->dest.reg == cfa->base) {
  59
  60                                 /* mov %reg, %rsp */