Messages in this thread Patch in this message | | | From | Alexandre Chartre <> | Subject | [PATCH V2 5/9] objtool: Add support for intra-function calls | Date | Tue, 7 Apr 2020 09:31:38 +0200 |
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Change objtool to support intra-function calls. On x86, 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> --- include/linux/frame.h | 11 +++ .../Documentation/stack-validation.txt | 8 ++ tools/objtool/arch.h | 2 + tools/objtool/arch/x86/decode.c | 12 +++ tools/objtool/check.c | 97 ++++++++++++++++--- tools/objtool/check.h | 1 + 6 files changed, 117 insertions(+), 14 deletions(-)
diff --git a/include/linux/frame.h b/include/linux/frame.h index 02d3ca2d9598..c7178e6c9d48 100644 --- a/include/linux/frame.h +++ b/include/linux/frame.h @@ -15,9 +15,20 @@ static void __used __section(.discard.func_stack_frame_non_standard) \ *__func_stack_frame_non_standard_##func = func +/* + * This macro indicates that the following intra-function call is valid. + * Any non-annotated intra-function call will cause objtool to issue warning. + */ +#define ANNOTATE_INTRA_FUNCTION_CALL \ + 999: \ + .pushsection .discard.intra_function_call; \ + .long 999b; \ + .popsection; + #else /* !CONFIG_STACK_VALIDATION */ #define STACK_FRAME_NON_STANDARD(func) +#define ANNOTATE_INTRA_FUNCTION_CALL #endif /* CONFIG_STACK_VALIDATION */ diff --git a/tools/objtool/Documentation/stack-validation.txt b/tools/objtool/Documentation/stack-validation.txt index de094670050b..09f863fd32d2 100644 --- a/tools/objtool/Documentation/stack-validation.txt +++ b/tools/objtool/Documentation/stack-validation.txt @@ -290,6 +290,14 @@ they mean, and suggestions for how to fix them. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646 +9. file.o: warning: unsupported intra-function call + + This warning means that a direct call is done to a destination which + is not at the beginning of a function. If this is a legit call, you + can remove this warning by putting the ANNOTATE_INTRA_FUNCTION_CALL + directive right before the call. + + If the error doesn't seem to make sense, it could be a bug in objtool. Feel free to ask the objtool maintainer for help. diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h index ced3765c4f44..4d42c12d9957 100644 --- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -75,4 +75,6 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, bool arch_callee_saved_reg(unsigned char reg); +void arch_configure_intra_function_call(struct stack_op *op); + #endif /* _ARCH_H */ diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index a62e032863a8..7ee1561bf7ad 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -497,3 +497,15 @@ void arch_initial_func_cfi_state(struct cfi_state *state) state->regs[16].base = CFI_CFA; state->regs[16].offset = -8; } + + +void arch_configure_intra_function_call(struct stack_op *op) +{ + /* + * For the impact on the stack, make an intra-function + * call behaves like a push of an immediate value (the + * return address). + */ + op->src.type = OP_SRC_CONST; + op->dest.type = OP_DEST_PUSH; +} diff --git a/tools/objtool/check.c b/tools/objtool/check.c index ab06e9bdd396..bf1e4e94d686 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -644,34 +644,50 @@ static int add_jump_destinations(struct objtool_file *file) return 0; } +static int configure_call(struct objtool_file *file, struct instruction *insn) +{ + unsigned long dest_off; + + dest_off = insn->offset + insn->len + insn->immediate; + insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); + if (insn->call_dest) { + /* regular call */ + return 0; + } + + /* intra-function call */ + if (!insn->intra_function_call) + WARN_FUNC("intra-function call", insn->sec, insn->offset); + + dest_off = insn->offset + insn->len + insn->immediate; + insn->jump_dest = find_insn(file, insn->sec, dest_off); + if (!insn->jump_dest) { + WARN_FUNC("can't find call dest at %s+0x%lx", + insn->sec, insn->offset, + insn->sec->name, dest_off); + return -1; + } + + return 0; +} + /* * Find the destination instructions for all calls. */ static int add_call_destinations(struct objtool_file *file) { struct instruction *insn; - unsigned long dest_off; struct rela *rela; for_each_insn(file, insn) { - if (insn->type != INSN_CALL) + if (insn->type != INSN_CALL || insn->ignore) continue; rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); if (!rela) { - dest_off = insn->offset + insn->len + insn->immediate; - insn->call_dest = find_symbol_by_offset(insn->sec, - dest_off); - - if (!insn->call_dest && !insn->ignore) { - WARN_FUNC("unsupported intra-function call", - insn->sec, insn->offset); - if (retpoline) - WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); + if (configure_call(file, insn)) return -1; - } - } else if (rela->sym->type == STT_SECTION) { insn->call_dest = find_symbol_by_offset(rela->sym->sec, rela->addend+4); @@ -1293,6 +1309,43 @@ 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 direct call", + insn->sec, insn->offset); + return -1; + } + + arch_configure_intra_function_call(&insn->stack_op); + insn->intra_function_call = true; + } + + return 0; +} + static void mark_rodata(struct objtool_file *file) { struct section *sec; @@ -1348,6 +1401,10 @@ 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; @@ -2110,7 +2167,8 @@ 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; @@ -2119,6 +2177,17 @@ 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 7a91497fee7e..7c7ec3d8fb00 100644 --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -36,6 +36,7 @@ struct instruction { unsigned int alt_group; bool dead_end, ignore, ignore_alts; bool hint, save, restore; + bool intra_function_call; bool retpoline_safe; u8 visited; u8 ret_offset; -- 2.18.2
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