lkml.org 
[lkml]   [2018]   [Apr]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.14 083/138] objtool: Add Clang support
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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.git.jpoimboe@redhat.com
    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 */

    \
     
     \ /
      Last update: 2018-04-11 00:54    [W:4.164 / U:0.252 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site