All of lore.kernel.org
 help / color / mirror / Atom feed
From: Nick Desaulniers <ndesaulniers@google.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Mark Brown <broonie@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] Documentation: asm-annotation: clarify .L local symbol names
Date: Wed, 13 Jan 2021 09:46:20 -0800	[thread overview]
Message-ID: <20210113174620.958429-1-ndesaulniers@google.com> (raw)
In-Reply-To: <20210113165923.acvycpcu5tzksbbi@treble>

Use more precise language and move the text to a region in the docs to
show that this constraint is not just for SYM_CODE_START*.

Suggested-by: Mark Brown <broonie@kernel.org>
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 Documentation/asm-annotations.rst | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/Documentation/asm-annotations.rst b/Documentation/asm-annotations.rst
index e711ff98102a..76424e0431f4 100644
--- a/Documentation/asm-annotations.rst
+++ b/Documentation/asm-annotations.rst
@@ -100,6 +100,11 @@ Instruction Macros
 ~~~~~~~~~~~~~~~~~~
 This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above.
 
+``objtool`` requires that all code must be contained in an ELF symbol. Symbol
+names that have a ``.L`` prefix do not emit symbol table entries. ``.L``
+prefixed symbols can be used within a code region, but should be avoided for
+denoting a range of code via ``SYM_*_START/END`` annotations.
+
 * ``SYM_FUNC_START`` and ``SYM_FUNC_START_LOCAL`` are supposed to be **the
   most frequent markings**. They are used for functions with standard calling
   conventions -- global and local. Like in C, they both align the functions to
@@ -153,15 +158,6 @@ This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above.
   To some extent, this category corresponds to deprecated ``ENTRY`` and
   ``END``. Except ``END`` had several other meanings too.
 
-  Developers should avoid using local symbol names that are prefixed with
-  ``.L``, as this has special meaning for the assembler; a symbol entry will
-  not be emitted into the symbol table. This can prevent ``objtool`` from
-  generating correct unwind info. Symbols with STB_LOCAL binding may still be
-  used, and ``.L`` prefixed local symbol names are still generally useable
-  within a function, but ``.L`` prefixed local symbol names should not be used
-  to denote the beginning or end of code regions via
-  ``SYM_CODE_START_LOCAL``/``SYM_CODE_END``.
-
 * ``SYM_INNER_LABEL*`` is used to denote a label inside some
   ``SYM_{CODE,FUNC}_START`` and ``SYM_{CODE,FUNC}_END``.  They are very similar
   to C labels, except they can be made global. An example of use::
-- 
2.30.0.284.gd98b1dd5eaa7-goog


  reply	other threads:[~2021-01-13 17:47 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
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                           ` Nick Desaulniers [this message]
2021-01-13 19:56                             ` [PATCH] Documentation: asm-annotation: clarify .L local symbol names 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210113174620.958429-1-ndesaulniers@google.com \
    --to=ndesaulniers@google.com \
    --cc=bp@alien8.de \
    --cc=broonie@kernel.org \
    --cc=corbet@lwn.net \
    --cc=jpoimboe@redhat.com \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=mingo@redhat.com \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.