From: hpa@zytor.com
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
torvalds@linux-foundation.org, tglx@linutronix.de,
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, luto@kernel.org,
bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org,
dvyukov@google.com, rostedt@goodmis.org
Subject: Re: [PATCH 00/20] objtool: UACCESS validation v3
Date: Thu, 07 Mar 2019 09:29:17 -0800 [thread overview]
Message-ID: <714E9D57-CCAE-4A69-AC3E-E6AFC525834E@zytor.com> (raw)
In-Reply-To: <20190307171829.xww7is5qja32r7ux@treble>
On March 7, 2019 9:18:29 AM PST, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>On Thu, Mar 07, 2019 at 09:04:36AM -0800, hpa@zytor.com wrote:
>> On March 7, 2019 8:47:05 AM PST, Josh Poimboeuf <jpoimboe@redhat.com>
>wrote:
>> >On Thu, Mar 07, 2019 at 02:13:12PM +0100, Peter Zijlstra wrote:
>> >> On Thu, Mar 07, 2019 at 01:55:26PM +0100, Peter Zijlstra wrote:
>> >> > On Thu, Mar 07, 2019 at 01:03:17PM +0100, Peter Zijlstra wrote:
>> >>
>> >>
>> >> > > 01be 20d3: 31 c0 xor %eax,%eax
>> >> > > 01c0 20d5: 4c 39 eb cmp %r13,%rbx
>> >> > > 01c3 20d8: 77 08 ja 20e2
>> ><__do_sys_waitid+0x1cd>
>> >>
>> >> randconfig-build/kernel/exit.o: warning: objtool:
>> >__do_sys_waitid()+0x1c3: (branch)
>> >>
>> >> > > 01cd 20e2: 83 f0 01 xor $0x1,%eax
>> >> > > 01d0 20e5: 48 89 c2 mov %rax,%rdx
>> >> > > 01d3 20e8: 83 e2 01 and $0x1,%edx
>> >> > > 01d6 20eb: 48 83 c2 02 add $0x2,%rdx
>> >> > > 01da 20ef: 48 ff 04 d5 00 00 00 incq 0x0(,%rdx,8)
>> >> > > 01e1 20f6: 00
>> >> > > 01de 20f3: R_X86_64_32S _ftrace_branch+0x148
>> >> > > 01e2 20f7: 84 c0 test %al,%al
>> >> > > 01e4 20f9: 75 2d jne 2128
>> ><__do_sys_waitid+0x213>
>> >> >
>> >> > we do not take this branch and fall-through.
>> >>
>> >> And that is the error, I think. We should've taken it and went to:
>> >>
>> >> return -EFAULT;
>> >>
>> >> because:
>> >>
>> >> +1be xor %eax,%eax eax=0
>> >> +1cd xor $0x1,%eax eax=1
>> >> +1e2 test %al,%al 1&1==1 -> ZF=0
>> >> +1e4 jnz
>> >>
>> >> Is an unconditional code sequence, but there's no way objtool can
>do
>> >> that without becoming a full blown interpreter :/
>> >>
>> >> > > 0213 2128: 49 c7 c7 f2 ff ff ff mov
>> >$0xfffffffffffffff2,%r15
>> >> > > ffffffffffffe0eb }
>> >> > > 021a 212f: 48 8d 65 d8 lea
>-0x28(%rbp),%rsp
>> >> > > 021e 2133: 4c 89 f8 mov %r15,%rax
>> >> > > 0221 2136: 5b pop %rbx
>> >> > > 0222 2137: 41 5c pop %r12
>> >> > > 0224 2139: 41 5d pop %r13
>> >> > > 0226 213b: 41 5e pop %r14
>> >> > > 0228 213d: 41 5f pop %r15
>> >> > > 022a 213f: 5d pop %rbp
>> >> > > 022b 2140: c3 retq
>> >
>> >This "fixes" it, and also seems to help -Os make much code:
>> >
>> >diff --git a/include/linux/compiler.h b/include/linux/compiler.h
>> >index 445348facea9..8de63db58fdd 100644
>> >--- a/include/linux/compiler.h
>> >+++ b/include/linux/compiler.h
>> >@@ -67,7 +67,7 @@ void ftrace_likely_update(struct
>ftrace_likely_data
>> >*f, int val,
>> > .line = __LINE__, \
>> > }; \
>> > ______r = !!(cond); \
>> >- ______f.miss_hit[______r]++; \
>> >+ if (______r) ______f.miss_hit[1]++; else ______f.miss_hit[0]++; \
>> > ______r; \
>> > }))
>> > #endif /* CONFIG_PROFILE_ALL_BRANCHES */
>>
>> if (cond)? Or is ___r used elsewhere?
>
>______r is also the return value. And it's needed because cond should
>only be evaluated once.
So put a true; and false; inside the if.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2019-03-07 17:30 UTC|newest]
Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-07 11:45 [PATCH 00/20] objtool: UACCESS validation v3 Peter Zijlstra
2019-03-07 11:45 ` [PATCH 01/20] x86/ia32: Fix ia32_restore_sigcontext AC leak Peter Zijlstra
2019-03-07 11:45 ` [PATCH 02/20] i915,uaccess: Fix redundant CLAC Peter Zijlstra
2019-03-07 11:45 ` [PATCH 03/20] x86/uaccess: Move copy_user_handle_tail into asm Peter Zijlstra
2019-03-08 18:53 ` Josh Poimboeuf
2019-03-08 19:48 ` Peter Zijlstra
2019-03-08 19:53 ` Josh Poimboeuf
2019-03-10 13:22 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 04/20] x86/uaccess: Fix up the fixup Peter Zijlstra
2019-03-07 11:45 ` [PATCH 05/20] x86/uaccess/xen: Suppress SMAP warnings Peter Zijlstra
2019-03-07 12:22 ` Juergen Gross
2019-03-07 12:32 ` Peter Zijlstra
2019-03-07 12:36 ` Juergen Gross
2019-03-08 19:00 ` Josh Poimboeuf
2019-03-08 19:03 ` Josh Poimboeuf
2019-03-10 13:19 ` Peter Zijlstra
2019-03-11 17:59 ` Josh Poimboeuf
2019-03-08 19:50 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 06/20] x86/uaccess: Always inline user_access_begin() Peter Zijlstra
2019-03-07 11:45 ` [PATCH 07/20] x86/uaccess: Always inline force_valid_ss() Peter Zijlstra
2019-03-07 13:50 ` Peter Zijlstra
2019-03-07 18:05 ` Andy Lutomirski
2019-03-07 18:59 ` Peter Zijlstra
2019-03-07 19:06 ` Andy Lutomirski
2019-03-07 11:45 ` [PATCH 08/20] x86/uaccess: Introduce user_access_{save,restore}() Peter Zijlstra
2019-03-07 11:45 ` [PATCH 09/20] x86/uaccess,kasan: Fix KASAN vs SMAP Peter Zijlstra
2019-03-07 11:45 ` [PATCH 10/20] x86/uaccess,ubsan: Fix UBSAN " Peter Zijlstra
2019-03-07 11:45 ` [PATCH 11/20] x86/uaccess,ftrace: Fix ftrace_likely_update() " Peter Zijlstra
2019-03-07 11:45 ` [PATCH 12/20] objtool: Set insn->func for alternatives Peter Zijlstra
2019-03-08 19:16 ` Josh Poimboeuf
2019-03-08 19:51 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 13/20] objtool: Hande function aliases Peter Zijlstra
2019-03-08 19:23 ` Josh Poimboeuf
2019-03-08 19:52 ` Peter Zijlstra
2019-03-08 20:00 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 14/20] objtool: Rewrite add_ignores() Peter Zijlstra
2019-03-08 19:29 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 15/20] objtool: Add --backtrace support Peter Zijlstra
2019-03-08 19:33 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 16/20] objtool: Rewrite alt->skip_orig Peter Zijlstra
2019-03-08 20:15 ` Josh Poimboeuf
2019-03-08 21:34 ` Peter Zijlstra
2019-03-08 22:27 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 17/20] objtool: Fix sibling call detection Peter Zijlstra
2019-03-08 20:22 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 18/20] objtool: Add UACCESS validation Peter Zijlstra
2019-03-07 16:33 ` Linus Torvalds
2019-03-07 17:10 ` hpa
2019-03-07 17:41 ` Peter Zijlstra
2019-03-07 17:54 ` Linus Torvalds
2019-03-07 18:48 ` Peter Zijlstra
2019-03-07 18:51 ` hpa
2019-03-07 19:03 ` Peter Zijlstra
2019-03-08 15:01 ` Josh Poimboeuf
2019-03-08 15:07 ` Peter Zijlstra
2019-03-07 20:23 ` Peter Zijlstra
2019-03-07 20:40 ` Peter Zijlstra
2019-03-08 15:07 ` Josh Poimboeuf
2019-03-08 15:23 ` Peter Zijlstra
2019-03-07 20:15 ` Andrey Ryabinin
2019-03-07 20:33 ` Peter Zijlstra
2019-03-07 20:40 ` Andrey Ryabinin
2019-03-07 20:42 ` Peter Zijlstra
2019-03-08 21:02 ` Josh Poimboeuf
2019-03-08 21:31 ` Peter Zijlstra
2019-03-08 21:54 ` Josh Poimboeuf
2019-03-10 13:10 ` Peter Zijlstra
2019-03-11 18:01 ` Josh Poimboeuf
2019-03-07 11:45 ` [PATCH 19/20] objtool: uaccess PUSHF/POPF support Peter Zijlstra
2019-03-08 21:11 ` Josh Poimboeuf
2019-03-10 13:12 ` Peter Zijlstra
2019-03-07 11:45 ` [PATCH 20/20] objtool: Add Direction Flag validation Peter Zijlstra
2019-03-08 21:16 ` Josh Poimboeuf
2019-03-08 21:33 ` Peter Zijlstra
2019-03-08 21:56 ` Josh Poimboeuf
2019-03-10 13:13 ` Peter Zijlstra
2019-03-11 18:00 ` Josh Poimboeuf
2019-03-07 12:03 ` [PATCH 00/20] objtool: UACCESS validation v3 Peter Zijlstra
2019-03-07 12:55 ` Peter Zijlstra
2019-03-07 13:13 ` Peter Zijlstra
2019-03-07 16:47 ` Josh Poimboeuf
2019-03-07 16:50 ` Josh Poimboeuf
2019-03-07 17:00 ` Linus Torvalds
2019-03-07 17:17 ` Josh Poimboeuf
2019-03-07 17:38 ` Peter Zijlstra
2019-03-07 17:45 ` Linus Torvalds
2019-03-07 18:18 ` Steven Rostedt
2019-03-10 13:16 ` Peter Zijlstra
2019-04-19 10:08 ` [PATCH] compiler.h, tracing: Remove CONFIG_PROFILE_ALL_BRANCHES Ingo Molnar
2019-04-19 13:04 ` Steven Rostedt
2019-03-07 17:04 ` [PATCH 00/20] objtool: UACCESS validation v3 hpa
2019-03-07 17:18 ` Josh Poimboeuf
2019-03-07 17:29 ` hpa [this message]
2019-03-07 17:45 ` Josh Poimboeuf
2019-03-07 17:48 ` Linus Torvalds
2019-03-07 17:43 ` Peter Zijlstra
2019-03-07 17:48 ` Josh Poimboeuf
2019-04-03 8:21 ` [tip:core/objtool] tracing: Improve "if" macro code generation tip-bot for Josh Poimboeuf
2019-03-07 16:31 ` [PATCH 00/20] objtool: UACCESS validation v3 Linus Torvalds
2019-03-07 17:14 ` hpa
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