Messages in this thread Patch in this message | | | From | Tiezhu Yang <> | Subject | [PATCH] objtool: Check local label in is_sibling_call() and add_jump_destinations() | Date | Tue, 15 Aug 2023 16:36:02 +0800 |
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When update the latest upstream gcc and binutils which enables linker relaxation by default, it generates more objtool warnings on LoongArch, like this:
init/version.o: warning: objtool: early_hostname+0x20: sibling call from callable instruction with modified stack frame
We can see that the branch and jump operation about local label ".L2" is not sibling call, because a sibling call is a tail-call to another symbol. In this case, make is_sibling_call() return false, set dest_sec and dest_off to calculate jump_dest in add_jump_destinations().
Here are some detailed info: [fedora@linux 6.5.test]$ gcc --version gcc (GCC) 14.0.0 20230803 (experimental) [fedora@linux 6.5.test]$ as --version GNU assembler (GNU Binutils) 2.41.50.20230803 [fedora@linux 6.5.test]$ objdump -M no-aliases -D init/version.o 0000000000000000 <early_hostname>: 0: 00150085 or $a1, $a0, $zero 4: 1a000004 pcalau12i $a0, 0 8: 02ffc063 addi.d $sp, $sp, -16 c: 02810406 addi.w $a2, $zero, 65 10: 02c00084 addi.d $a0, $a0, 0 14: 29c02061 st.d $ra, $sp, 8 18: 54000000 bl 0 # 18 <early_hostname+0x18> 1c: 0281000c addi.w $t0, $zero, 64 20: 6c001584 bgeu $t0, $a0, 20 # 34 <.L2> 24: 1a000004 pcalau12i $a0, 0 28: 02810005 addi.w $a1, $zero, 64 2c: 02c00084 addi.d $a0, $a0, 0 30: 54000000 bl 0 # 30 <early_hostname+0x30>
0000000000000034 <.L2>: 34: 28c02061 ld.d $ra, $sp, 8 38: 00150004 or $a0, $zero, $zero 3c: 02c04063 addi.d $sp, $sp, 16 40: 4c000020 jirl $zero, $ra, 0
By the way, it need to move insn_reloc() before is_sibling_call() to avoid implicit declaration build error.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> --- tools/objtool/check.c | 69 ++++++++++++++++++++++++++++++--------------------- 1 file changed, 41 insertions(+), 28 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 8936a05..fea3675 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -161,12 +161,39 @@ static bool is_jump_table_jump(struct instruction *insn) insn_jump_table(alt_group->orig_group->first_insn); } -static bool is_sibling_call(struct instruction *insn) +static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) +{ + struct reloc *reloc; + + if (insn->no_reloc) + return NULL; + + if (!file) + return NULL; + + reloc = find_reloc_by_dest_range(file->elf, insn->sec, + insn->offset, insn->len); + if (!reloc) { + insn->no_reloc = 1; + return NULL; + } + + return reloc; +} + +static bool is_sibling_call(struct objtool_file *file, struct instruction *insn) { /* * Assume only STT_FUNC calls have jump-tables. */ if (insn_func(insn)) { + struct reloc *reloc = insn_reloc(file, insn); + + /* Disallow sibling calls into STT_NOTYPE if it is local lable */ + if (reloc && reloc->sym->type == STT_NOTYPE && + strncmp(reloc->sym->name, ".L", 2) == 0) + return false; + /* An indirect jump is either a sibling call or a jump to a table. */ if (insn->type == INSN_JUMP_DYNAMIC) return !is_jump_table_jump(insn); @@ -232,7 +259,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, * of the sibling call returns. */ func_for_each_insn(file, func, insn) { - if (is_sibling_call(insn)) { + if (is_sibling_call(file, insn)) { struct instruction *dest = insn->jump_dest; if (!dest) @@ -743,7 +770,7 @@ static int create_static_call_sections(struct objtool_file *file) if (!elf_init_reloc_data_sym(file->elf, sec, idx * sizeof(*site) + 4, (idx * 2) + 1, key_sym, - is_sibling_call(insn) * STATIC_CALL_SITE_TAIL)) + is_sibling_call(file, insn) * STATIC_CALL_SITE_TAIL)) return -1; idx++; @@ -1298,26 +1325,6 @@ __weak bool arch_is_rethunk(struct symbol *sym) return false; } -static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) -{ - struct reloc *reloc; - - if (insn->no_reloc) - return NULL; - - if (!file) - return NULL; - - reloc = find_reloc_by_dest_range(file->elf, insn->sec, - insn->offset, insn->len); - if (!reloc) { - insn->no_reloc = 1; - return NULL; - } - - return reloc; -} - static void remove_insn_ops(struct instruction *insn) { struct stack_op *op, *next; @@ -1560,8 +1567,14 @@ static int add_jump_destinations(struct objtool_file *file) * External sibling call or internal sibling call with * STT_FUNC reloc. */ - add_call_dest(file, insn, reloc->sym, true); - continue; + if (reloc->sym->type == STT_NOTYPE && + strncmp(reloc->sym->name, ".L", 2) == 0) { + dest_sec = insn->sec; + dest_off = arch_jump_destination(insn); + } else { + add_call_dest(file, insn, reloc->sym, true); + continue; + } } else if (reloc->sym->sec->idx) { dest_sec = reloc->sym->sec; dest_off = reloc->sym->sym.st_value + @@ -3649,7 +3662,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, case INSN_JUMP_CONDITIONAL: case INSN_JUMP_UNCONDITIONAL: - if (is_sibling_call(insn)) { + if (is_sibling_call(file, insn)) { ret = validate_sibling_call(file, insn, &state); if (ret) return ret; @@ -3670,7 +3683,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, case INSN_JUMP_DYNAMIC: case INSN_JUMP_DYNAMIC_CONDITIONAL: - if (is_sibling_call(insn)) { + if (is_sibling_call(file, insn)) { ret = validate_sibling_call(file, insn, &state); if (ret) return ret; @@ -3834,7 +3847,7 @@ static int validate_unret(struct objtool_file *file, struct instruction *insn) case INSN_JUMP_UNCONDITIONAL: case INSN_JUMP_CONDITIONAL: - if (!is_sibling_call(insn)) { + if (!is_sibling_call(file, insn)) { if (!insn->jump_dest) { WARN_INSN(insn, "unresolved jump target after linking?!?"); return -1; -- 2.1.0
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