From: Andy Lutomirski <luto@kernel.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
live-patching@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>, Jiri Slaby <jslaby@suse.cz>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH 05/10] objtool, x86: add facility for asm code to provide CFI hints
Date: Thu, 1 Jun 2017 06:57:24 -0700 [thread overview]
Message-ID: <CALCETrXsLqsqYWFcjQBw-F_booEAfLKhG+EEZtBfrDcntEgjvg@mail.gmail.com> (raw)
In-Reply-To: <5ec63cefd2093152464b7bb1383938f6970e65eb.1496293620.git.jpoimboe@redhat.com>
On Wed, May 31, 2017 at 10:44 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> Some asm (and inline asm) code does special things to the stack which
> objtool can't understand. (Nor can GCC or GNU assembler, for that
> matter.) In such cases we need a facility for the code to provide
> annotations, so the unwinder can unwind through it.
>
> This provides such a facility, in the form of CFI hints. They're
> similar to the GNU assembler .cfi* directives, but they give more
> information, and are needed in far fewer places, because objtool can
> fill in the blanks by following branches and adjusting the stack pointer
> for pushes and pops.
Two minor suggestions:
Could you prefix these with something other than "CFI_"? For those of
use who have read the binutils manual, using "CFI_" sounds awfully
like .cfi_, and people might expect the semantics to be the same.
> +#define CFI_HINT(cfa_reg, cfa_offset, type) \
> + "999: \n\t" \
Have you checked if 999 is used elsewhere? My personal preference is to use:
.Ldescriptive_text_\@:
instead of a hopefully-unique number. I never researched the history,
but I suspect that the convention of using large numbers came from
early binutils versions that didn't have \@, but we use \@ fairly
extensively in the kernel these days, so it would seem that we no
longer support binutils versions that old.
next prev parent reply other threads:[~2017-06-01 13:57 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 5:44 [RFC PATCH 00/10] x86: undwarf unwinder Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 01/10] objtool: move checking code to check.c Josh Poimboeuf
2017-06-14 7:22 ` Jiri Slaby
2017-06-01 5:44 ` [RFC PATCH 02/10] objtool, x86: add several functions and files to the objtool whitelist Josh Poimboeuf
2017-06-14 7:24 ` Jiri Slaby
2017-06-14 13:03 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 03/10] objtool: stack validation 2.0 Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 04/10] objtool: add undwarf debuginfo generation Josh Poimboeuf
2017-06-14 8:42 ` Jiri Slaby
2017-06-14 13:27 ` Josh Poimboeuf
2017-06-22 7:47 ` Jiri Slaby
2017-06-22 12:49 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 05/10] objtool, x86: add facility for asm code to provide CFI hints Josh Poimboeuf
2017-06-01 13:57 ` Andy Lutomirski [this message]
2017-06-01 14:16 ` Josh Poimboeuf
2017-06-01 14:40 ` Andy Lutomirski
2017-06-01 15:02 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 06/10] x86/entry: add CFI hint undwarf annotations Josh Poimboeuf
2017-06-01 14:03 ` Andy Lutomirski
2017-06-01 14:23 ` Josh Poimboeuf
2017-06-01 14:28 ` Josh Poimboeuf
2017-06-01 14:39 ` Andy Lutomirski
2017-06-01 15:01 ` Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 07/10] x86/asm: add CFI hint annotations to sync_core() Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 08/10] extable: rename 'sortextable' script to 'sorttable' Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 09/10] extable: add undwarf table sorting ability to sorttable script Josh Poimboeuf
2017-06-01 5:44 ` [RFC PATCH 10/10] x86/unwind: add undwarf unwinder Josh Poimboeuf
2017-06-01 11:05 ` Peter Zijlstra
2017-06-01 12:26 ` Josh Poimboeuf
2017-06-01 12:47 ` Jiri Slaby
2017-06-01 13:02 ` Josh Poimboeuf
2017-06-01 13:42 ` Peter Zijlstra
2017-06-01 13:10 ` Peter Zijlstra
2017-06-01 12:13 ` Peter Zijlstra
2017-06-01 12:36 ` Josh Poimboeuf
2017-06-01 13:12 ` Peter Zijlstra
2017-06-01 15:03 ` Josh Poimboeuf
2017-06-14 11:45 ` Jiri Slaby
2017-06-14 13:44 ` Josh Poimboeuf
2017-06-01 6:08 ` [RFC PATCH 00/10] x86: " Ingo Molnar
2017-06-01 11:58 ` Josh Poimboeuf
2017-06-01 12:17 ` Peter Zijlstra
2017-06-01 12:33 ` Jiri Slaby
2017-06-01 12:52 ` Josh Poimboeuf
2017-06-01 12:57 ` Jiri Slaby
2017-06-01 12:47 ` Josh Poimboeuf
2017-06-01 13:25 ` Peter Zijlstra
2017-06-06 14:14 ` Sergey Senozhatsky
2017-06-01 13:50 ` Andy Lutomirski
2017-06-01 13:50 ` Ingo Molnar
2017-06-01 13:58 ` Jiri Slaby
2017-06-02 8:30 ` Jiri Slaby
2017-06-01 14:05 ` Josh Poimboeuf
2017-06-01 14:08 ` Jiri Slaby
2017-06-02 10:40 ` Mel Gorman
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