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
next prev parent reply other threads:[~2021-01-13 17:47 UTC|newest]
Thread overview: 30+ 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
2021-01-13 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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