Messages in this thread Patch in this message | | | Date | Wed, 20 Oct 2021 12:44:44 +0200 | From | Peter Zijlstra <> | Subject | [PATCH v2 02/14] objtool: Explicitly avoid self modifying code in .altinstr_replacement |
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Assume ALTERNATIVE()s know what they're doing and do not change, or cause to change, instructions in .altinstr_replacement sections.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- tools/objtool/check.c | 42 +++++++++++++++++++++++++++++++----------- 1 file changed, 31 insertions(+), 11 deletions(-)
--- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -993,18 +993,27 @@ static void remove_insn_ops(struct instr } } -static void add_call_dest(struct objtool_file *file, struct instruction *insn, - struct symbol *dest, bool sibling) +static void annotate_call_site(struct objtool_file *file, + struct instruction *insn, bool sibling) { struct reloc *reloc = insn_reloc(file, insn); + struct symbol *sym = insn->call_dest; - insn->call_dest = dest; - if (!dest) + if (!sym) + sym = reloc->sym; + + /* + * Alternative replacement code is just template code which is + * sometimes copied to the original instruction, For now, don't + * annotate it. (In the future we might consider annotating the + * original instruction if/when it ever makes sense to do so.). + */ + if (!strcmp(insn->sec->name, ".altinstr_replacement")) return; - if (insn->call_dest->static_call_tramp) { - list_add_tail(&insn->call_node, - &file->static_call_list); + if (sym->static_call_tramp) { + list_add_tail(&insn->call_node, &file->static_call_list); + return; } /* @@ -1013,7 +1022,7 @@ static void add_call_dest(struct objtool * text. */ if (insn->sec->noinstr && - !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) { + !strncmp(sym->name, "__sanitizer_cov_", 16)) { if (reloc) { reloc->type = R_NONE; elf_write_reloc(file->elf, reloc); @@ -1025,9 +1034,10 @@ static void add_call_dest(struct objtool : arch_nop_insn(insn->len)); insn->type = sibling ? INSN_RETURN : INSN_NOP; + return; } - if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) { + if (mcount && !strcmp(sym->name, "__fentry__")) { if (sibling) WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset); @@ -1042,9 +1052,17 @@ static void add_call_dest(struct objtool insn->type = INSN_NOP; - list_add_tail(&insn->mcount_loc_node, - &file->mcount_loc_list); + list_add_tail(&insn->mcount_loc_node, &file->mcount_loc_list); + return; } +} + +static void add_call_dest(struct objtool_file *file, struct instruction *insn, + struct symbol *dest, bool sibling) +{ + insn->call_dest = dest; + if (!dest) + return; /* * Whatever stack impact regular CALLs have, should be undone @@ -1054,6 +1072,8 @@ static void add_call_dest(struct objtool * are converted to JUMP, see read_intra_function_calls(). */ remove_insn_ops(insn); + + annotate_call_site(file, insn, sibling); } /*
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