From b735bd3e68824316655252a931a3353a6ebc036f Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Thu, 21 Jan 2021 15:29:24 -0600 Subject: objtool: Combine UNWIND_HINT_RET_OFFSET and UNWIND_HINT_FUNC The ORC metadata generated for UNWIND_HINT_FUNC isn't actually very func-like. With certain usages it can cause stack state mismatches because it doesn't set the return address (CFI_RA). Also, users of UNWIND_HINT_RET_OFFSET no longer need to set a custom return stack offset. Instead they just need to specify a func-like situation, so the current ret_offset code is hacky for no good reason. Solve both problems by simplifying the RET_OFFSET handling and converting it into a more useful UNWIND_HINT_FUNC. If we end up needing the old 'ret_offset' functionality again in the future, we should be able to support it pretty easily with the addition of a custom 'sp_offset' in UNWIND_HINT_FUNC. Signed-off-by: Josh Poimboeuf Link: https://lore.kernel.org/r/db9d1f5d79dddfbb3725ef6d8ec3477ad199948d.1611263462.git.jpoimboe@redhat.com --- tools/objtool/check.c | 37 +++++++++++++++---------------------- 1 file changed, 15 insertions(+), 22 deletions(-) (limited to 'tools/objtool/check.c') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index b4e1655017de..f88f20327bf2 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1404,13 +1404,20 @@ static int add_jump_table_alts(struct objtool_file *file) return 0; } +static void set_func_state(struct cfi_state *state) +{ + state->cfa = initial_func_cfi.cfa; + memcpy(&state->regs, &initial_func_cfi.regs, + CFI_NUM_REGS * sizeof(struct cfi_reg)); + state->stack_size = initial_func_cfi.cfa.offset; +} + static int read_unwind_hints(struct objtool_file *file) { struct section *sec, *relocsec; struct reloc *reloc; struct unwind_hint *hint; struct instruction *insn; - struct cfi_reg *cfa; int i; sec = find_section_by_name(file->elf, ".discard.unwind_hints"); @@ -1445,22 +1452,20 @@ static int read_unwind_hints(struct objtool_file *file) return -1; } - cfa = &insn->cfi.cfa; + insn->hint = true; - if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) { - insn->ret_offset = bswap_if_needed(hint->sp_offset); + if (hint->type == UNWIND_HINT_TYPE_FUNC) { + set_func_state(&insn->cfi); continue; } - insn->hint = true; - if (arch_decode_hint_reg(insn, hint->sp_reg)) { WARN_FUNC("unsupported unwind_hint sp base reg %d", insn->sec, insn->offset, hint->sp_reg); return -1; } - cfa->offset = bswap_if_needed(hint->sp_offset); + insn->cfi.cfa.offset = bswap_if_needed(hint->sp_offset); insn->cfi.type = hint->type; insn->cfi.end = hint->end; } @@ -1716,27 +1721,18 @@ static bool is_fentry_call(struct instruction *insn) static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state) { - u8 ret_offset = insn->ret_offset; struct cfi_state *cfi = &state->cfi; int i; if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap) return true; - if (cfi->cfa.offset != initial_func_cfi.cfa.offset + ret_offset) + if (cfi->cfa.offset != initial_func_cfi.cfa.offset) return true; - if (cfi->stack_size != initial_func_cfi.cfa.offset + ret_offset) + if (cfi->stack_size != initial_func_cfi.cfa.offset) return true; - /* - * If there is a ret offset hint then don't check registers - * because a callee-saved register might have been pushed on - * the stack. - */ - if (ret_offset) - return false; - for (i = 0; i < CFI_NUM_REGS; i++) { if (cfi->regs[i].base != initial_func_cfi.regs[i].base || cfi->regs[i].offset != initial_func_cfi.regs[i].offset) @@ -2880,10 +2876,7 @@ static int validate_section(struct objtool_file *file, struct section *sec) continue; init_insn_state(&state, sec); - state.cfi.cfa = initial_func_cfi.cfa; - memcpy(&state.cfi.regs, &initial_func_cfi.regs, - CFI_NUM_REGS * sizeof(struct cfi_reg)); - state.cfi.stack_size = initial_func_cfi.cfa.offset; + set_func_state(&state.cfi); warnings += validate_symbol(file, sec, func, &state); } -- cgit v1.2.3