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From: Borislav Petkov <bp@alien8.de>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: "Nick Desaulniers" <ndesaulniers@google.com>,
	"Fāng-ruì Sòng" <maskray@google.com>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>, "Arnd Bergmann" <arnd@arndb.de>,
	"X86 ML" <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	"Nathan Chancellor" <natechancellor@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v3] x86/entry: emit a symbol for register restoring thunk
Date: Tue, 12 Jan 2021 12:54:21 +0100	[thread overview]
Message-ID: <20210112115421.GB13086@zn.tnic> (raw)
In-Reply-To: <20210112015952.jdystnwkvuxsrwa2@treble>

On Mon, Jan 11, 2021 at 07:59:52PM -0600, Josh Poimboeuf wrote:
> Right.  In the vast majority of cases, .L symbols are totally fine.
> 
> The limitation now being imposed by objtool (due to these assembler
> changes) is that all code must be contained in an ELF symbol.  And .L
> symbols don't create such symbols.
> 
> So basically, you can use an .L symbol *inside* a function or a code
> segment, you just can't use the .L symbol to contain the code using a
> SYM_*_START/END annotation pair.
> 
> It only affects a tiny fraction of all .L usage.  Just a handful of code
> sites I think.

@Nick, this belongs into the commit message too pls.

Also,

Documentation/asm-annotations.rst
include/linux/linkage.h

would need some of that blurb added explaining to users *why* they
should not use .L local symbols as SYM_* macro arguments.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  reply	other threads:[~2021-01-12 11:55 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-23 23:21 [PATCH] x86/entry: use STB_GLOBAL for register restoring thunk Nick Desaulniers
2020-12-24  4:55 ` Josh Poimboeuf
2021-01-06  0:43   ` [PATCH v2] " Nick Desaulniers
2021-01-06  1:58     ` Josh Poimboeuf
2021-01-11 20:38       ` [PATCH v3] x86/entry: emit a symbol " Nick Desaulniers
2021-01-11 20:58         ` Fangrui Song
2021-01-11 22:09           ` Josh Poimboeuf
2021-01-11 22:16             ` Fāng-ruì Sòng
2021-01-11 22:12         ` Josh Poimboeuf
2021-01-12  0:38         ` Borislav Petkov
2021-01-12  0:41           ` Fāng-ruì Sòng
2021-01-12  1:00             ` Borislav Petkov
2021-01-12  1:13               ` Nick Desaulniers
2021-01-12  1:59                 ` Josh Poimboeuf
2021-01-12 11:54                   ` Borislav Petkov [this message]
2021-01-12 19:46                     ` [PATCH v4] " Nick Desaulniers
2021-01-12 21:01                       ` Mark Brown
2021-01-13 16:59                         ` Josh Poimboeuf
2021-01-13 17:46                           ` [PATCH] Documentation: asm-annotation: clarify .L local symbol names Nick Desaulniers
2021-01-13 19:56                             ` Mark Brown
2021-01-13 17:56                           ` [PATCH v4] x86/entry: emit a symbol for register restoring thunk Nick Desaulniers
2021-01-14 10:39                             ` Borislav Petkov
2021-01-14 11:36                               ` Peter Zijlstra
2021-01-14 13:28                                 ` [PATCH] x86/entry: Remove put_ret_addr_in_rdi THUNK macro argument Borislav Petkov
2021-01-14 15:53                                   ` Peter Zijlstra
2021-01-19 10:12                                 ` [tip: x86/entry] " tip-bot2 for Borislav Petkov
2021-01-14 15:14                               ` [PATCH v4] x86/entry: emit a symbol for register restoring thunk Josh Poimboeuf
2021-01-14 11:49                         ` [Linux-kernel-mentees] Fwd: " Lukas Bulwahn
2021-01-14 14:21                           ` Aditya
2021-01-14 14:35                             ` Lukas Bulwahn
2021-01-13 11:52                       ` [tip: x86/entry] x86/entry: Emit " tip-bot2 for Nick Desaulniers
2021-01-19 10:12                       ` tip-bot2 for Nick Desaulniers
2021-01-12 11:47                 ` [PATCH v3] x86/entry: emit " Borislav Petkov

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