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    Subject[PATCH 4.19 214/245] objtool: Fix noreturn detection for ignored functions
    Date
    From: Josh Poimboeuf <jpoimboe@redhat.com>

    [ Upstream commit db6c6a0df840e3f52c84cc302cc1a08ba11a4416 ]

    When a function is annotated with STACK_FRAME_NON_STANDARD, objtool
    doesn't validate its code paths. It also skips sibling call detection
    within the function.

    But sibling call detection is actually needed for the case where the
    ignored function doesn't have any return instructions. Otherwise
    objtool naively marks the function as implicit static noreturn, which
    affects the reachability of its callers, resulting in "unreachable
    instruction" warnings.

    Fix it by just enabling sibling call detection for ignored functions.
    The 'insn->ignore' check in add_jump_destinations() is no longer needed
    after

    e6da9567959e ("objtool: Don't use ignore flag for fake jumps").

    Fixes the following warning:

    arch/x86/kvm/vmx/vmx.o: warning: objtool: vmx_handle_exit_irqoff()+0x142: unreachable instruction

    which triggers on an allmodconfig with CONFIG_GCOV_KERNEL unset.

    Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
    Link: https://lkml.kernel.org/r/5b1e2536cdbaa5246b60d7791b76130a74082c62.1599751464.git.jpoimboe@redhat.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/objtool/check.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/tools/objtool/check.c b/tools/objtool/check.c
    index fd3071d83deae..c0ab27368a345 100644
    --- a/tools/objtool/check.c
    +++ b/tools/objtool/check.c
    @@ -503,7 +503,7 @@ static int add_jump_destinations(struct objtool_file *file)
    insn->type != INSN_JUMP_UNCONDITIONAL)
    continue;

    - if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
    + if (insn->offset == FAKE_JUMP_OFFSET)
    continue;

    rela = find_rela_by_dest_range(insn->sec, insn->offset,
    --
    2.25.1


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