Messages in this thread Patch in this message | | | From | Alexandre Chartre <> | Subject | [PATCH 3/7] objtool: Add support for intra-function calls | Date | Thu, 2 Apr 2020 10:22:16 +0200 |
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Change objtool to support intra-function calls. An intra-function call is represented in objtool as a push onto the stack (of the return address), and a jump to the destination address. That way the stack information is correctly updated and the call flow is still accurate.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> --- tools/objtool/check.c | 73 ++++++++++++++++++++++++++++++++++++++++++- tools/objtool/check.h | 1 + 2 files changed, 73 insertions(+), 1 deletion(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 214809ac2776..0cec91291d46 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -657,6 +657,18 @@ static int add_call_destinations(struct objtool_file *file) if (insn->type != INSN_CALL) continue; + if (insn->intra_function_call) { + dest_off = insn->offset + insn->len + insn->immediate; + insn->jump_dest = find_insn(file, insn->sec, dest_off); + if (insn->jump_dest) + continue; + + WARN_FUNC("can't find call dest at %s+0x%lx", + insn->sec, insn->offset, + insn->sec->name, dest_off); + return -1; + } + rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); if (!rela) { @@ -1289,6 +1301,49 @@ static int read_retpoline_hints(struct objtool_file *file) return 0; } +static int read_intra_function_call(struct objtool_file *file) +{ + struct section *sec; + struct instruction *insn; + struct rela *rela; + + sec = find_section_by_name(file->elf, + ".rela.discard.intra_function_call"); + if (!sec) + return 0; + + list_for_each_entry(rela, &sec->rela_list, list) { + if (rela->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", + sec->name); + return -1; + } + + insn = find_insn(file, rela->sym->sec, rela->addend); + if (!insn) { + WARN("bad .discard.intra_function_call entry"); + return -1; + } + + if (insn->type != INSN_CALL) { + WARN_FUNC("intra_function_call not a call", + insn->sec, insn->offset); + return -1; + } + + insn->intra_function_call = true; + /* + * For the impact on the stack, make an intra-function + * call behaves like a push of an immediate value (the + * return address). + */ + insn->stack_op.src.type = OP_SRC_CONST; + insn->stack_op.dest.type = OP_DEST_PUSH; + } + + return 0; +} + static void mark_rodata(struct objtool_file *file) { struct section *sec; @@ -1344,6 +1399,10 @@ static int decode_sections(struct objtool_file *file) if (ret) return ret; + ret = read_intra_function_call(file); + if (ret) + return ret; + ret = add_call_destinations(file); if (ret) return ret; @@ -2092,7 +2151,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, return ret; if (!no_fp && func && !is_fentry_call(insn) && - !has_valid_stack_frame(&state)) { + !has_valid_stack_frame(&state) && + !insn->intra_function_call) { WARN_FUNC("call without frame pointer save/setup", sec, insn->offset); return 1; @@ -2101,6 +2161,17 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, if (dead_end_function(file, insn->call_dest)) return 0; + if (insn->intra_function_call) { + update_insn_state(insn, &state); + ret = validate_branch(file, func, insn, + insn->jump_dest, state); + if (ret) { + if (backtrace) + BT_FUNC("(intra-call)", insn); + return ret; + } + } + break; case INSN_JUMP_CONDITIONAL: diff --git a/tools/objtool/check.h b/tools/objtool/check.h index cffb23d81782..2bd6d2f46baa 100644 --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -35,6 +35,7 @@ struct instruction { unsigned long immediate; unsigned int alt_group; bool dead_end, ignore, hint, save, restore, ignore_alts; + bool intra_function_call; bool retpoline_safe; u8 visited; struct symbol *call_dest; -- 2.18.2
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