From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: 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, luto@kernel.org,
bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org,
dvyukov@google.com, rostedt@goodmis.org
Subject: Re: [PATCH 03/20] x86/uaccess: Move copy_user_handle_tail into asm
Date: Sun, 10 Mar 2019 14:22:14 +0100 [thread overview]
Message-ID: <20190310132214.GN2482@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20190308195302.popw53eqeoozg53r@treble>
On Fri, Mar 08, 2019 at 01:53:02PM -0600, Josh Poimboeuf wrote:
> On Fri, Mar 08, 2019 at 08:48:35PM +0100, Peter Zijlstra wrote:
> > On Fri, Mar 08, 2019 at 12:53:21PM -0600, Josh Poimboeuf wrote:
> > > On Thu, Mar 07, 2019 at 12:45:14PM +0100, Peter Zijlstra wrote:
> > > > /*
> > > > + * Try to copy last bytes and clear the rest if needed.
> > > > + * Since protection fault in copy_from/to_user is not a normal situation,
> > > > + * it is not necessary to optimize tail handling.
> > > > + *
> > > > + * Input:
> > > > + * rdi destination
> > > > + * rsi source
> > > > + * rdx count
> > > > + *
> > > > + * Output:
> > > > + * eax uncopied bytes or 0 if successful.
> > > > + */
> > > > +ALIGN;
> > > > +copy_user_handle_tail:
> > > > + movl %edx,%ecx
> > > > +1: rep movsb
> > > > +2: mov %ecx,%eax
> > > > + ASM_CLAC
> > > > + ret
> > > > +
> > > > + _ASM_EXTABLE_UA(1b, 2b)
> > > > +ENDPROC(copy_user_handle_tail)
> > >
> > > This is an unstructured piece of code rather than a callable function,
> > > END would probably be more appropriate. Or maybe it should just be a
> > > local label (.Lcopy_user_handle_tail) because I don't think the
> > > alignment and ELF symbol size are even needed.
> >
> > ENDPROC makes it STT_FUNC and gets us stricter AC tests.
>
> How so? I would have thought the opposite. Doesn't objtool only follow
> a jump if its destination is to a non-function? Otherwise it's
> considered a sibling call.
Normally yes, but we don't do that for .fixup I think. And by setting
STT_FUNC we enable the 'redundant CLAC' warning, which is ignored for
!STT_FUNC.
next prev parent reply other threads:[~2019-03-10 13:22 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 [this message]
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
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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