From 0d0970eef3b03ef08b19da5bc3044410731cf38f Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Wed, 20 Sep 2017 16:24:32 -0500 Subject: 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 Signed-off-by: Josh Poimboeuf Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Dmitriy Vyukov Cc: Linus Torvalds Cc: Matthias Kaehlcke Cc: Miguel Bernal Marin Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- tools/objtool/arch/x86/decode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'tools/objtool/arch') 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; } -- cgit v1.2.3 From 607a4029d439cdfa258aff5da32bb9cd6ed1a66d Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Wed, 27 Sep 2017 10:36:38 -0500 Subject: objtool: Support unoptimized frame pointer setup Arnd Bergmann reported a bunch of warnings like: crypto/jitterentropy.o: warning: objtool: jent_fold_time()+0x3b: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_stuck()+0x1d: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_unbiased_bit()+0x15: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_read_entropy()+0x32: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_entropy_collector_free()+0x19: call without frame pointer save/setup and arch/x86/events/core.o: warning: objtool: collect_events uses BP as a scratch register arch/x86/events/core.o: warning: objtool: events_ht_sysfs_show()+0x22: call without frame pointer save/setup With certain rare configurations, GCC sometimes sets up the frame pointer with: lea (%rsp),%rbp instead of: mov %rsp,%rbp The instructions are equivalent, so treat the former like the latter. Reported-by: Arnd Bergmann Signed-off-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/a468af8b28a69b83fffc6d7668be9b6fcc873699.1506526584.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- tools/objtool/arch/x86/decode.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'tools/objtool/arch') diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 0f22768c0d4d..34a579f806e3 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -284,11 +284,16 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, case 0x8d: if (sib == 0x24 && rex_w && !rex_b && !rex_x) { - /* lea disp(%rsp), reg */ *type = INSN_STACK; - op->src.type = OP_SRC_ADD; + if (!insn.displacement.value) { + /* lea (%rsp), reg */ + op->src.type = OP_SRC_REG; + } else { + /* lea disp(%rsp), reg */ + op->src.type = OP_SRC_ADD; + op->src.offset = insn.displacement.value; + } op->src.reg = CFI_SP; - op->src.offset = insn.displacement.value; op->dest.type = OP_DEST_REG; op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r]; -- cgit v1.2.3