Unlike the jump_label bits, static_cpu_has is implemented with alternatives. We use the new type field to distinguish them from any other alternatives
Like jump_labels, make static_cpu_has set static_jump_dest on the instructions after the static branch such that we can assert on it. Cc: Borislav Petkov <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Josh Poimboeuf <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> --- tools/objtool/check.c | 21 +++++++++++++++++++++ tools/objtool/special.c | 11 +++++++++++ tools/objtool/special.h | 1 + 3 files changed, 33 insertions(+) --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -636,6 +636,12 @@ static int handle_group_alt(struct objto fake_jump->ignore = true; if (!special_alt->new_len) { + /* + * The NOP case for _static_cpu_has() + */ + if (special_alt->static_feat) + fake_jump->jump_dest->static_jump_dest = true; + *new_insn = fake_jump; return 0; } @@ -664,6 +670,21 @@ static int handle_group_alt(struct objto insn->sec, insn->offset); return -1; } + + if (special_alt->static_feat) { + if (insn->type != INSN_JUMP_UNCONDITIONAL) { + WARN_FUNC("not an unconditional jump in _static_cpu_has()", + insn->sec, insn->offset); + } + if (insn->jump_dest == fake_jump) { + WARN_FUNC("jump inside alternative for _static_cpu_has()", + insn->sec, insn->offset); + } + /* + * The JMP+disp case for _static_cpu_has() + */ + insn->jump_dest->static_jump_dest = true; + } } if (!last_new_insn) { --- a/tools/objtool/special.c +++ b/tools/objtool/special.c @@ -40,6 +40,11 @@ #define ALT_FEATURE_OFFSET 8 #define ALT_ORIG_LEN_OFFSET 10 #define ALT_NEW_LEN_OFFSET 11 +#define ALT_PADDING_OFFSET 12 +#define ALT_TYPE_OFFSET 13 + +#define ALT_TYPE_DEFAULT 0 +#define ALT_TYPE_STATIC_CPU_HAS 1 #define X86_FEATURE_POPCNT (4*32+23) @@ -99,10 +104,13 @@ static int get_alt_entry(struct elf *elf if (entry->feature) { unsigned short feature; + unsigned char type; feature = *(unsigned short *)(sec->data->d_buf + offset + entry->feature); + type = *(unsigned char *)(sec->data->d_buf + offset + ALT_TYPE_OFFSET); + /* * It has been requested that we don't validate the !POPCNT * feature path which is a "very very small percentage of @@ -110,6 +118,9 @@ static int get_alt_entry(struct elf *elf */ if (feature == X86_FEATURE_POPCNT) alt->skip_orig = true; + + if (type == ALT_TYPE_STATIC_CPU_HAS) + alt->static_feat = true; } orig_rela = find_rela_by_dest(sec, offset + entry->orig); --- a/tools/objtool/special.h +++ b/tools/objtool/special.h @@ -27,6 +27,7 @@ struct special_alt { bool group; bool skip_orig; bool jump_or_nop; + bool static_feat; struct section *orig_sec; unsigned long orig_off;
