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    Subject[PATCH v2 12/14] objtool: Allow archs to rewrite retpolines
    When retpolines are employed, compilers typically emit calls to
    retpoline thunks. Objtool recognises these calls and marks them as
    dynamic calls.

    Provide infrastructure for architectures to rewrite/augment what the
    compiler wrote for us.

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    ---
    tools/objtool/check.c | 23 +++++++++++++++++++++--
    tools/objtool/include/objtool/arch.h | 3 +++
    2 files changed, 24 insertions(+), 2 deletions(-)

    --- a/tools/objtool/check.c
    +++ b/tools/objtool/check.c
    @@ -852,6 +852,14 @@ __weak bool arch_is_retpoline(struct sym
    return false;
    }

    +
    +__weak int arch_rewrite_retpoline(struct objtool_file *file,
    + struct instruction *insn,
    + struct reloc *reloc)
    +{
    + return 0;
    +}
    +
    /*
    * Find the destination instructions for all jumps.
    */
    @@ -885,6 +893,9 @@ static int add_jump_destinations(struct
    insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;

    insn->retpoline_safe = true;
    +
    + arch_rewrite_retpoline(file, insn, reloc);
    +
    continue;
    } else if (insn->func) {
    /* internal or external sibling call (with reloc) */
    @@ -1036,6 +1047,8 @@ static int add_call_destinations(struct
    insn->type = INSN_CALL_DYNAMIC;
    insn->retpoline_safe = true;

    + arch_rewrite_retpoline(file, insn, reloc);
    +
    remove_insn_ops(insn);
    continue;

    @@ -1212,6 +1225,8 @@ static int handle_group_alt(struct objto
    dest_off = arch_jump_destination(insn);
    if (dest_off == special_alt->new_off + special_alt->new_len)
    insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
    + else
    + insn->jump_dest = find_insn(file, insn->sec, dest_off);

    if (!insn->jump_dest) {
    WARN_FUNC("can't find alternative jump destination",
    @@ -1797,11 +1812,15 @@ static int decode_sections(struct objtoo
    if (ret)
    return ret;

    - ret = add_jump_destinations(file);
    + /*
    + * Must be before add_{jump,call}_destination; for they can add
    + * magic alternatives.
    + */
    + ret = add_special_section_alts(file);
    if (ret)
    return ret;

    - ret = add_special_section_alts(file);
    + ret = add_jump_destinations(file);
    if (ret)
    return ret;

    --- a/tools/objtool/include/objtool/arch.h
    +++ b/tools/objtool/include/objtool/arch.h
    @@ -82,6 +82,9 @@ unsigned long arch_jump_destination(stru
    unsigned long arch_dest_reloc_offset(int addend);

    const char *arch_nop_insn(int len);
    +int arch_rewrite_retpoline(struct objtool_file *file,
    + struct instruction *insn,
    + struct reloc *reloc);

    int arch_decode_hint_reg(struct instruction *insn, u8 sp_reg);


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