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Date: Fri, 19 Feb 2016 05:45:53 -0800 From: "Luis R. Rodriguez" <mcgrof@...nel.org> To: hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de Cc: x86@...nel.org, linux-kernel@...r.kernel.org, luto@...capital.net, boris.ostrovsky@...cle.com, rusty@...tcorp.com.au, david.vrabel@...rix.com, konrad.wilk@...cle.com, mcb30@...e.org, jgross@...e.com, ming.lei@...onical.com, gregkh@...uxfoundation.org, arnd@...db.de, linux-arch@...r.kernel.org, linux@....linux.org.uk, benh@...nel.crashing.org, jbaron@...mai.com, ananth@...ibm.com, anil.s.keshavamurthy@...el.com, davem@...emloft.net, masami.hiramatsu.pt@...achi.com, andriy.shevchenko@...ux.intel.com, dwmw2@...radead.org, xen-devel@...ts.xensource.com, "Luis R. Rodriguez" <mcgrof@...nel.org> Subject: [RFC v2 1/7] sections.h: add sections header to collect all section info Linux makes extensive use of custom ELF header sections, documentation for these are well scatterred. Unify this documentation in a central place. Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org> --- Documentation/DocBook/Makefile | 3 +- Documentation/DocBook/sections.tmpl | 99 ++++++++++++++++ include/linux/sections.h | 224 ++++++++++++++++++++++++++++++++++++ 3 files changed, 325 insertions(+), 1 deletion(-) create mode 100644 Documentation/DocBook/sections.tmpl create mode 100644 include/linux/sections.h diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index d70f9b68174e..f2dfd46bf30a 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -15,7 +15,8 @@ DOCBOOKS := z8530book.xml device-drivers.xml \ 80211.xml debugobjects.xml sh.xml regulator.xml \ alsa-driver-api.xml writing-an-alsa-driver.xml \ tracepoint.xml gpu.xml media_api.xml w1.xml \ - writing_musb_glue_layer.xml crypto-API.xml iio.xml + writing_musb_glue_layer.xml crypto-API.xml iio.xml \ + sections.xml include Documentation/DocBook/media/Makefile diff --git a/Documentation/DocBook/sections.tmpl b/Documentation/DocBook/sections.tmpl new file mode 100644 index 000000000000..96d8d88c1b93 --- /dev/null +++ b/Documentation/DocBook/sections.tmpl @@ -0,0 +1,99 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE set PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" + "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> +<set> + <setinfo> + <title>Linux ELF sections</title> + <subtitle> + Explains Linux ELF sections + </subtitle> + + <copyright> + <year>2016</year> + <holder>Luis R. Rodriguez</holder> + </copyright> + + <authorgroup> + <author> + <firstname>Luis</firstname> + <surname>Rodriguez</surname> + <affiliation> + <address><email>mcgrof@...nel.org</email></address> + </affiliation> + </author> + </authorgroup> + + <legalnotice> + <para> + This documentation is free software; you can redistribute + it and/or modify it under the terms of the GNU General Public + License version 2 as published by the Free Software Foundation. + </para> + <para> + This documentation is distributed in the hope that it will be + useful, but WITHOUT ANY WARRANTY; without even the implied + warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. + See the GNU General Public License for more details. + </para> + <para> + You should have received a copy of the GNU General Public + License along with this documentation; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, + MA 02111-1307 USA + </para> + <para> + For more details see the file COPYING in the source + distribution of Linux. + </para> + </legalnotice> + + <abstract> + <para> + This book documents the different custom ELF sections used on the Linux + kernel and defined on Linux's custom linker script. + </para> + </abstract> + </setinfo> + <book id="linux-elf-sections"> + <bookinfo> + <title>Linux kernel ELF sections</title> + + <abstract> +!Pinclude/linux/sections.h Introduction + </abstract> + </bookinfo> + + <chapter> + <title>Core Linux kernel sections</title> +!Pinclude/linux/sections.h Core Linux kernel sections +!Finclude/linux/sections.h SECTION_RODATA +!Pinclude/linux/sections.h SECTION_TEXT +!Pinclude/linux/sections.h SECTION_DATA + </chapter> + + <chapter> + <title>Linux .init* sections</title> +!Pinclude/linux/sections.h Linux init sections +!Finclude/linux/sections.h SECTION_INIT_DATA +!Finclude/linux/sections.h SECTION_INIT_RODATA +!Finclude/linux/sections.h SECTION_INIT_CALL + </chapter> + + <chapter> + <title>Linux .exit* sections</title> +!Pinclude/linux/sections.h Linux exit sections +!Finclude/linux/sections.h SECTION_EXIT +!Finclude/linux/sections.h SECTION_EXIT_DATA +!Finclude/linux/sections.h SECTION_EXIT_CALL + </chapter> + + <chapter> + <title>Linux .ref* sections</title> +!Pinclude/linux/sections.h Linux references to init sections +!Finclude/linux/sections.h SECTION_REF +!Finclude/linux/sections.h SECTION_REF_DATA +!Finclude/linux/sections.h SECTION_REF_RODATA + </chapter> + + </book> +</set> diff --git a/include/linux/sections.h b/include/linux/sections.h new file mode 100644 index 000000000000..7b47bea4956a --- /dev/null +++ b/include/linux/sections.h @@ -0,0 +1,224 @@ +#ifndef _LINUX_SECTIONS_H +#define _LINUX_SECTIONS_H +/* + * Linux ELF sections + * + * Copyright (C) 2016 Luis R. Rodriguez <mcgrof@...nel.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * Due to this file being licensed under the GPL there is controversy over + * whether this permits you to write a module that #includes this file + * without placing your module under the GPL. Please consult a lawyer for + * advice before doing this. + */ + +/** + * DOC: Introduction + * + * The Linux vmlinux binary uses a custom linker script which adds + * some custom specialized ELF sections. This aims to document those + * sections. Each section must document the goal of the section, and + * address concurrency considerations when applicable. + */ + +/** + * DOC: Core Linux kernel sections + * + * These are the core Linux kernel sections. + */ + +/** + * SECTION_RODATA - read only data + * + * Macro name for code which must be protected from write access. + */ +#define SECTION_RODATA .rodata + +/** + * SECTION_TEXT - kernel code execution section, read-only + * + * Macro name used to annotate code (functions) used during regular + * kernel run time. This is combined with SECTION_RODATA, only this + * section also gets execution allowed. + * + */ +#define SECTION_TEXT .text + +/** + * SECTION_DATA - for read-write data + * + * Macro name for read-write data. + */ +#define SECTION_DATA .data + +/** + * DOC: Linux init sections + * + * These sections are used for code and data structures used during boot or + * module initialization. On architectures that support it (x86, x86_64), all + * this code is freed up by the kernel right before the fist userspace init + * process is called when built-in to the kernel, and if modular it is freed + * after module initialization. Since the code is freed so early, in theory + * there should be no races against freeing this code with other CPUs. Init + * section code and data structures should never be exported with + * EXPORT_SYMBOL*() as the code will quickly become unavailable to the kernel + * after bootup. + */ + +/** + * SECTION_INIT - boot initialization code + * + * Macro name used to annotate code (functions) used only during boot or driver + * initialization. + * + */ +#define SECTION_INIT .init.text + +/** + * SECTION_INIT_DATA - boot initialization data + * + * Macro name used to annotate data structures used only during boot or driver + * initialization. + */ +#define SECTION_INIT_DATA .init.data + +/** + * SECTION_INIT_RODATA - boot read-only initialization data + * + * Macro name used to annotate read-only code (functions) used only during boot + * or driver initialization. + */ +#define SECTION_INIT_RODATA .init.rodata + +/** + * SECTION_INIT_CALL - special init call + * + * Special macro name used to annotate subsystem init call. These calls are + * are now grouped by functionality into separate subsections. Ordering inside + * the subsections is determined by link order. + */ +#define SECTION_INIT_CALL .initcall + +/** + * DOC: Linux exit sections + * + * These sections are used to declare a functions and data structures which + * are only required on exit, the function or data structure will be dropped + * if the code declaring this section is not compiled as a module on + * architectures that support this (x86, x86_64). There is no special case + * handling for this code when built-in to the kernel. + */ + +/** + * SECTION_EXIT - module exit code + * + * Macro name used to annotate code (functions) used only during module + * unload. + */ +#define SECTION_EXIT .exit.text + +/** + * SECTION_EXIT_DATA - module exit data structures + * + * Macro name used to annotate data structures used only during module + * unload. + */ +#define SECTION_EXIT_DATA .exit.data + +/** + * SECTION_EXIT_CALL - special exit call + * + * Special macro name used to annotate an exit exit routine, order + * is important and maintained by link order. + */ +#define SECTION_EXIT_CALL .exitcall.exit + +/** + * DOC: Linux references to init sections + * + * These sections are used to teach modpost to not warn about possible + * misuses of init section code from other sections. If you use this + * your use case should document why you are certain such use of init + * sectioned code is valid. For more details refer to include/linux/init.h + * __ref, __refdata, and __refconst documentation. + */ + +/** + * SECTION_REF - code referencing init is valid + * + * Macro name used to annotate that code (functions) declared with this section + * has been vetteed as valid for its reference or use of other code (functions) + * or data structures which are part of the init sections. + */ +#define SECTION_REF .ref.text + +/** + * SECTION_REF_DATA - reference data structure are valid + * + * Macro name used to annotate data structures declared with this section have + * been vetteed for its reference or use of other code (functions) or data + * structures part of the init sections. + */ +#define SECTION_REF_DATA .ref.data + +/** + * SECTION_REF_RODATA - const code or data structure referencing init is valid + * + * Macro name used to annotate const code (functions) const data structures which + * has been vetteed for its reference or use of other code (functions) or data + * structures part of the init sections. + */ +#define SECTION_REF_RODATA .ref.rodata + +/** + * DOC: Custom Linux sections + * + * These are very custom Linux sections. + */ + +#ifndef __ASSEMBLY__ + +/* + * Without this you end up with the section macro + * as part of the name + */ +#define __SECTION_TBL(section, name, level) \ + #section ".tbl." #name "." #level + +/** + * SECTION_TBL - Linux linker table section + * + * @section: respective section + * @name: used to describe the use case + * @level: the order-level for the linker table + * + * Macro name used to annotate a linker table. For more details refer to + * include/linux/tables.h. Linker tables use standard Linux sections defined + * in this file. + */ +#define SECTION_TBL(section, name, level) \ + __SECTION_TBL(section, name, level) + +/* + * For use on linker scripts and helpers + */ +#define ___SECTION_TBL(section, name) \ + section##.tbl.##name +/** + * SECTION_TBL_ALL - glob to capture all linker table uses for this section + * + * @section: respective section + * + * Macro name used by linker script to capture all linker tables uses for + * the given section. This is used by include/asm-generic/vmlinux.lds.h + */ +#define SECTION_TBL_ALL(section) \ + ___SECTION_TBL(section,*) + +#endif /* __ASSEMBLY__ */ + +#endif /* _LINUX_SECTIONS_H */ -- 2.7.0
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