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Mon, 18 Mar 2019 15:52:43 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id E53DB238A0160; Mon, 18 Mar 2019 16:52:38 +0100 (CET) Message-Id: <20190318155141.743508038@infradead.org> User-Agent: quilt/0.65 Date: Mon, 18 Mar 2019 16:39:00 +0100 From: Peter Zijlstra To: torvalds@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com, julien.thierry@arm.com, will.deacon@arm.com, luto@amacapital.net, mingo@kernel.org, catalin.marinas@arm.com, james.morse@arm.com, valentin.schneider@arm.com, brgerst@gmail.com, jpoimboe@redhat.com, luto@kernel.org, bp@alien8.de, dvlasenk@redhat.com Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, dvyukov@google.com, rostedt@goodmis.org Subject: [PATCH 20/25] objtool: Add --backtrace support References: <20190318153840.906404905@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For when you want to know the path that reached your fail state. $ ./objtool check --no-fp --backtrace arch/x86/lib/usercopy_64.o arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0x3: UACCESS disable without MEMOPs: __clear_user() arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x3a: (alt) arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x2e: (branch) arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x18: (branch) arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch) arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x5: (alt) arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x0: <=== (func) 0000000000000000 <__clear_user>: 0: e8 00 00 00 00 callq 5 <__clear_user+0x5> 1: R_X86_64_PLT32 __fentry__-0x4 5: 90 nop 6: 90 nop 7: 90 nop 8: 48 89 f0 mov %rsi,%rax b: 48 c1 ee 03 shr $0x3,%rsi f: 83 e0 07 and $0x7,%eax 12: 48 89 f1 mov %rsi,%rcx 15: 48 85 c9 test %rcx,%rcx 18: 74 0f je 29 <__clear_user+0x29> 1a: 48 c7 07 00 00 00 00 movq $0x0,(%rdi) 21: 48 83 c7 08 add $0x8,%rdi 25: ff c9 dec %ecx 27: 75 f1 jne 1a <__clear_user+0x1a> 29: 48 89 c1 mov %rax,%rcx 2c: 85 c9 test %ecx,%ecx 2e: 74 0a je 3a <__clear_user+0x3a> 30: c6 07 00 movb $0x0,(%rdi) 33: 48 ff c7 inc %rdi 36: ff c9 dec %ecx 38: 75 f6 jne 30 <__clear_user+0x30> 3a: 90 nop 3b: 90 nop 3c: 90 nop 3d: 48 89 c8 mov %rcx,%rax 40: c3 retq Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/builtin-check.c | 3 ++- tools/objtool/builtin.h | 2 +- tools/objtool/check.c | 18 ++++++++++++++---- tools/objtool/warn.h | 8 ++++++++ 4 files changed, 25 insertions(+), 6 deletions(-) --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -29,7 +29,7 @@ #include "builtin.h" #include "check.h" -bool no_fp, no_unreachable, retpoline, module; +bool no_fp, no_unreachable, retpoline, module, backtrace; static const char * const check_usage[] = { "objtool check [] file.o", @@ -41,6 +41,7 @@ const struct option check_options[] = { OPT_BOOLEAN('u', "no-unreachable", &no_unreachable, "Skip 'unreachable instruction' warnings"), OPT_BOOLEAN('r', "retpoline", &retpoline, "Validate retpoline assumptions"), OPT_BOOLEAN('m', "module", &module, "Indicates the object will be part of a kernel module"), + OPT_BOOLEAN('b', "backtrace", &backtrace, "unwind on error"), OPT_END(), }; --- a/tools/objtool/builtin.h +++ b/tools/objtool/builtin.h @@ -20,7 +20,7 @@ #include extern const struct option check_options[]; -extern bool no_fp, no_unreachable, retpoline, module; +extern bool no_fp, no_unreachable, retpoline, module, backtrace; extern int cmd_check(int argc, const char **argv); extern int cmd_orc(int argc, const char **argv); --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1885,8 +1885,11 @@ static int validate_branch(struct objtoo if (!insn->ignore_alts) { list_for_each_entry(alt, &insn->alts, list) { ret = validate_branch(file, alt->insn, state); - if (ret) - return 1; + if (ret) { + if (backtrace) + BT_FUNC("(alt)", insn); + return ret; + } } } @@ -1933,8 +1936,11 @@ static int validate_branch(struct objtoo insn->jump_dest->func->pfunc == func)) { ret = validate_branch(file, insn->jump_dest, state); - if (ret) - return 1; + if (ret) { + if (backtrace) + BT_FUNC("(branch)", insn); + return ret; + } } else if (func && has_modified_stack_frame(&state)) { WARN_FUNC("sibling call from callable instruction with modified stack frame", @@ -2005,6 +2011,8 @@ static int validate_unwind_hints(struct for_each_insn(file, insn) { if (insn->hint && !insn->visited) { ret = validate_branch(file, insn, state); + if (ret && backtrace) + BT_FUNC("<=== (hint)", insn); warnings += ret; } } @@ -2133,6 +2141,8 @@ static int validate_functions(struct obj continue; ret = validate_branch(file, insn, state); + if (ret && backtrace) + BT_FUNC("<=== (func)", insn); warnings += ret; } } --- a/tools/objtool/warn.h +++ b/tools/objtool/warn.h @@ -64,6 +64,14 @@ static inline char *offstr(struct sectio free(_str); \ }) +#define BT_FUNC(format, insn, ...) \ +({ \ + struct instruction *_insn = (insn); \ + char *_str = offstr(_insn->sec, _insn->offset); \ + WARN(" %s: " format, _str, ##__VA_ARGS__); \ + free(_str); \ +}) + #define WARN_ELF(format, ...) \ WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))