diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2017-09-20 16:24:32 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-09-23 15:06:19 +0200 |
| commit | 0d0970eef3b03ef08b19da5bc3044410731cf38f (patch) | |
| tree | 3cbc6c409fce79dddb54b110a557a78dc8720086 | |
| parent | 4ba55e65f471d011d3ba2ac2022180ea0877d68e (diff) | |
objtool: Handle another GCC stack pointer adjustment bug
The kbuild bot reported the following warning with GCC 4.4 and a
randconfig:
net/socket.o: warning: objtool: compat_sock_ioctl()+0x1083: stack state mismatch: cfa1=7+160 cfa2=-1+0
This is caused by another GCC non-optimization, where it backs up and
restores the stack pointer for no apparent reason:
2f91: 48 89 e0 mov %rsp,%rax
2f94: 4c 89 e7 mov %r12,%rdi
2f97: 4c 89 f6 mov %r14,%rsi
2f9a: ba 20 00 00 00 mov $0x20,%edx
2f9f: 48 89 c4 mov %rax,%rsp
This issue would have been happily ignored before the following commit:
dd88a0a0c861 ("objtool: Handle GCC stack pointer adjustment bug")
But now that objtool is paying attention to such stack pointer writes
to/from a register, it needs to understand them properly. In this case
that means recognizing that the "mov %rsp, %rax" instruction is
potentially a backup of the stack pointer.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: dd88a0a0c861 ("objtool: Handle GCC stack pointer adjustment bug")
Link: http://lkml.kernel.org/r/8c7aa8e9a36fbbb6655d9d8e7cea58958c912da8.1505942196.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | tools/objtool/arch/x86/decode.c | 6 | ||||
| -rw-r--r-- | tools/objtool/check.c | 43 |
2 files changed, 32 insertions, 17 deletions
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 0e8c8ec4fd4e..0f22768c0d4d 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -208,14 +208,14 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, break; case 0x89: - if (rex == 0x48 && modrm == 0xe5) { + if (rex_w && !rex_r && modrm_mod == 3 && modrm_reg == 4) { - /* mov %rsp, %rbp */ + /* mov %rsp, reg */ *type = INSN_STACK; op->src.type = OP_SRC_REG; op->src.reg = CFI_SP; op->dest.type = OP_DEST_REG; - op->dest.reg = CFI_BP; + op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b]; break; } diff --git a/tools/objtool/check.c b/tools/objtool/check.c index f744617c9946..a0c518ecf085 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1203,24 +1203,39 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state) switch (op->src.type) { case OP_SRC_REG: - if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP) { + if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && + cfa->base == CFI_SP && + regs[CFI_BP].base == CFI_CFA && + regs[CFI_BP].offset == -cfa->offset) { + + /* mov %rsp, %rbp */ + cfa->base = op->dest.reg; + state->bp_scratch = false; + } - if (cfa->base == CFI_SP && - regs[CFI_BP].base == CFI_CFA && - regs[CFI_BP].offset == -cfa->offset) { + else if (op->src.reg == CFI_SP && + op->dest.reg == CFI_BP && state->drap) { - /* mov %rsp, %rbp */ - cfa->base = op->dest.reg; - state->bp_scratch = false; - } + /* drap: mov %rsp, %rbp */ + regs[CFI_BP].base = CFI_BP; + regs[CFI_BP].offset = -state->stack_size; + state->bp_scratch = false; + } - else if (state->drap) { + else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { - /* drap: mov %rsp, %rbp */ - regs[CFI_BP].base = CFI_BP; - regs[CFI_BP].offset = -state->stack_size; - state->bp_scratch = false; - } + /* + * mov %rsp, %reg + * + * This is needed for the rare case where GCC + * does: + * + * mov %rsp, %rax + * ... + * mov %rax, %rsp + */ + state->vals[op->dest.reg].base = CFI_CFA; + state->vals[op->dest.reg].offset = -state->stack_size; } else if (op->dest.reg == cfa->base) { |