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kernel/include/linux/linkage.h
Peter Zijlstra d49a062621 arch: Introduce CONFIG_FUNCTION_ALIGNMENT 
Generic function-alignment infrastructure.

Architectures can select FUNCTION_ALIGNMENT_xxB symbols; the
FUNCTION_ALIGNMENT symbol is then set to the largest such selected
size, 0 otherwise.

From this the -falign-functions compiler argument and __ALIGN macro
are set.

This incorporates the DEBUG_FORCE_FUNCTION_ALIGN_64B knob and future
alignment requirements for x86_64 (later in this series) into a single
place.

NOTE: also removes the 0x90 filler byte from the generic __ALIGN
      primitive, that value makes no sense outside of x86.

NOTE: .balign 0 reverts to a no-op.

Requested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111143.719248727@infradead.org
2022-10-17 16:40:58 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_LINKAGE_H
#define _LINUX_LINKAGE_H
#include <linux/compiler_types.h>
#include <linux/stringify.h>
#include <linux/export.h>
#include <asm/linkage.h>
/* Some toolchains use other characters (e.g. '`') to mark new line in macro */
#ifndef ASM_NL
#define ASM_NL ;
#endif
#ifdef __cplusplus
#define CPP_ASMLINKAGE extern "C"
#else
#define CPP_ASMLINKAGE
#endif
#ifndef asmlinkage
#define asmlinkage CPP_ASMLINKAGE
#endif
#ifndef cond_syscall
#define cond_syscall(x) asm( \
".weak " __stringify(x) "\n\t" \
".set " __stringify(x) "," \
__stringify(sys_ni_syscall))
#endif
#ifndef SYSCALL_ALIAS
#define SYSCALL_ALIAS(alias, name) asm( \
".globl " __stringify(alias) "\n\t" \
".set " __stringify(alias) "," \
__stringify(name))
#endif
#define __page_aligned_data __section(".data..page_aligned") __aligned(PAGE_SIZE)
#define __page_aligned_bss __section(".bss..page_aligned") __aligned(PAGE_SIZE)
/*
* For assembly routines.
*
* Note when using these that you must specify the appropriate
* alignment directives yourself
*/
#define __PAGE_ALIGNED_DATA .section ".data..page_aligned", "aw"
#define __PAGE_ALIGNED_BSS .section ".bss..page_aligned", "aw"
/*
* This is used by architectures to keep arguments on the stack
* untouched by the compiler by keeping them live until the end.
* The argument stack may be owned by the assembly-language
* caller, not the callee, and gcc doesn't always understand
* that.
*
* We have the return value, and a maximum of six arguments.
*
* This should always be followed by a "return ret" for the
* protection to work (ie no more work that the compiler might
* end up needing stack temporaries for).
*/
/* Assembly files may be compiled with -traditional .. */
#ifndef __ASSEMBLY__
#ifndef asmlinkage_protect
# define asmlinkage_protect(n, ret, args...) do { } while (0)
#endif
#endif
#ifndef __ALIGN
#define __ALIGN .balign CONFIG_FUNCTION_ALIGNMENT
#define __ALIGN_STR __stringify(__ALIGN)
#endif
#ifdef __ASSEMBLY__
/* SYM_T_FUNC -- type used by assembler to mark functions */
#ifndef SYM_T_FUNC
#define SYM_T_FUNC STT_FUNC
#endif
/* SYM_T_OBJECT -- type used by assembler to mark data */
#ifndef SYM_T_OBJECT
#define SYM_T_OBJECT STT_OBJECT
#endif
/* SYM_T_NONE -- type used by assembler to mark entries of unknown type */
#ifndef SYM_T_NONE
#define SYM_T_NONE STT_NOTYPE
#endif
/* SYM_A_* -- align the symbol? */
#define SYM_A_ALIGN ALIGN
#define SYM_A_NONE /* nothing */
/* SYM_L_* -- linkage of symbols */
#define SYM_L_GLOBAL(name) .globl name
#define SYM_L_WEAK(name) .weak name
#define SYM_L_LOCAL(name) /* nothing */
#ifndef LINKER_SCRIPT
#define ALIGN __ALIGN
#define ALIGN_STR __ALIGN_STR
/* === DEPRECATED annotations === */
#ifndef CONFIG_ARCH_USE_SYM_ANNOTATIONS
#ifndef GLOBAL
/* deprecated, use SYM_DATA*, SYM_ENTRY, or similar */
#define GLOBAL(name) \
.globl name ASM_NL \
name:
#endif
#ifndef ENTRY
/* deprecated, use SYM_FUNC_START */
#define ENTRY(name) \
SYM_FUNC_START(name)
#endif
#endif /* CONFIG_ARCH_USE_SYM_ANNOTATIONS */
#endif /* LINKER_SCRIPT */
#ifndef CONFIG_ARCH_USE_SYM_ANNOTATIONS
#ifndef WEAK
/* deprecated, use SYM_FUNC_START_WEAK* */
#define WEAK(name) \
SYM_FUNC_START_WEAK(name)
#endif
#ifndef END
/* deprecated, use SYM_FUNC_END, SYM_DATA_END, or SYM_END */
#define END(name) \
.size name, .-name
#endif
/* If symbol 'name' is treated as a subroutine (gets called, and returns)
* then please use ENDPROC to mark 'name' as STT_FUNC for the benefit of
* static analysis tools such as stack depth analyzer.
*/
#ifndef ENDPROC
/* deprecated, use SYM_FUNC_END */
#define ENDPROC(name) \
SYM_FUNC_END(name)
#endif
#endif /* CONFIG_ARCH_USE_SYM_ANNOTATIONS */
/* === generic annotations === */
/* SYM_ENTRY -- use only if you have to for non-paired symbols */
#ifndef SYM_ENTRY
#define SYM_ENTRY(name, linkage, align...) \
linkage(name) ASM_NL \
align ASM_NL \
name:
#endif
/* SYM_START -- use only if you have to */
#ifndef SYM_START
#define SYM_START(name, linkage, align...) \
SYM_ENTRY(name, linkage, align)
#endif
/* SYM_END -- use only if you have to */
#ifndef SYM_END
#define SYM_END(name, sym_type) \
.type name sym_type ASM_NL \
.set .L__sym_size_##name, .-name ASM_NL \
.size name, .L__sym_size_##name
#endif
/* SYM_ALIAS -- use only if you have to */
#ifndef SYM_ALIAS
#define SYM_ALIAS(alias, name, linkage) \
linkage(alias) ASM_NL \
.set alias, name ASM_NL
#endif
/* === code annotations === */
/*
* FUNC -- C-like functions (proper stack frame etc.)
* CODE -- non-C code (e.g. irq handlers with different, special stack etc.)
*
* Objtool validates stack for FUNC, but not for CODE.
* Objtool generates debug info for both FUNC & CODE, but needs special
* annotations for each CODE's start (to describe the actual stack frame).
*
* 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.
*
* ALIAS -- does not generate debug info -- the aliased function will
*/
/* SYM_INNER_LABEL_ALIGN -- only for labels in the middle of code */
#ifndef SYM_INNER_LABEL_ALIGN
#define SYM_INNER_LABEL_ALIGN(name, linkage) \
.type name SYM_T_NONE ASM_NL \
SYM_ENTRY(name, linkage, SYM_A_ALIGN)
#endif
/* SYM_INNER_LABEL -- only for labels in the middle of code */
#ifndef SYM_INNER_LABEL
#define SYM_INNER_LABEL(name, linkage) \
.type name SYM_T_NONE ASM_NL \
SYM_ENTRY(name, linkage, SYM_A_NONE)
#endif
/* SYM_FUNC_START -- use for global functions */
#ifndef SYM_FUNC_START
#define SYM_FUNC_START(name) \
SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
#endif
/* SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment */
#ifndef SYM_FUNC_START_NOALIGN
#define SYM_FUNC_START_NOALIGN(name) \
SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
#endif
/* SYM_FUNC_START_LOCAL -- use for local functions */
#ifndef SYM_FUNC_START_LOCAL
#define SYM_FUNC_START_LOCAL(name) \
SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)
#endif
/* SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o alignment */
#ifndef SYM_FUNC_START_LOCAL_NOALIGN
#define SYM_FUNC_START_LOCAL_NOALIGN(name) \
SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
#endif
/* SYM_FUNC_START_WEAK -- use for weak functions */
#ifndef SYM_FUNC_START_WEAK
#define SYM_FUNC_START_WEAK(name) \
SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN)
#endif
/* SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment */
#ifndef SYM_FUNC_START_WEAK_NOALIGN
#define SYM_FUNC_START_WEAK_NOALIGN(name) \
SYM_START(name, SYM_L_WEAK, SYM_A_NONE)
#endif
/*
* SYM_FUNC_END -- the end of SYM_FUNC_START_LOCAL, SYM_FUNC_START,
* SYM_FUNC_START_WEAK, ...
*/
#ifndef SYM_FUNC_END
#define SYM_FUNC_END(name) \
SYM_END(name, SYM_T_FUNC)
#endif
/*
* SYM_FUNC_ALIAS -- define a global alias for an existing function
*/
#ifndef SYM_FUNC_ALIAS
#define SYM_FUNC_ALIAS(alias, name) \
SYM_ALIAS(alias, name, SYM_L_GLOBAL)
#endif
/*
* SYM_FUNC_ALIAS_LOCAL -- define a local alias for an existing function
*/
#ifndef SYM_FUNC_ALIAS_LOCAL
#define SYM_FUNC_ALIAS_LOCAL(alias, name) \
SYM_ALIAS(alias, name, SYM_L_LOCAL)
#endif
/*
* SYM_FUNC_ALIAS_WEAK -- define a weak global alias for an existing function
*/
#ifndef SYM_FUNC_ALIAS_WEAK
#define SYM_FUNC_ALIAS_WEAK(alias, name) \
SYM_ALIAS(alias, name, SYM_L_WEAK)
#endif
/* SYM_CODE_START -- use for non-C (special) functions */
#ifndef SYM_CODE_START
#define SYM_CODE_START(name) \
SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
#endif
/* SYM_CODE_START_NOALIGN -- use for non-C (special) functions, w/o alignment */
#ifndef SYM_CODE_START_NOALIGN
#define SYM_CODE_START_NOALIGN(name) \
SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
#endif
/* SYM_CODE_START_LOCAL -- use for local non-C (special) functions */
#ifndef SYM_CODE_START_LOCAL
#define SYM_CODE_START_LOCAL(name) \
SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)
#endif
/*
* SYM_CODE_START_LOCAL_NOALIGN -- use for local non-C (special) functions,
* w/o alignment
*/
#ifndef SYM_CODE_START_LOCAL_NOALIGN
#define SYM_CODE_START_LOCAL_NOALIGN(name) \
SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
#endif
/* SYM_CODE_END -- the end of SYM_CODE_START_LOCAL, SYM_CODE_START, ... */
#ifndef SYM_CODE_END
#define SYM_CODE_END(name) \
SYM_END(name, SYM_T_NONE)
#endif
/* === data annotations === */
/* SYM_DATA_START -- global data symbol */
#ifndef SYM_DATA_START
#define SYM_DATA_START(name) \
SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
#endif
/* SYM_DATA_START -- local data symbol */
#ifndef SYM_DATA_START_LOCAL
#define SYM_DATA_START_LOCAL(name) \
SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
#endif
/* SYM_DATA_END -- the end of SYM_DATA_START symbol */
#ifndef SYM_DATA_END
#define SYM_DATA_END(name) \
SYM_END(name, SYM_T_OBJECT)
#endif
/* SYM_DATA_END_LABEL -- the labeled end of SYM_DATA_START symbol */
#ifndef SYM_DATA_END_LABEL
#define SYM_DATA_END_LABEL(name, linkage, label) \
linkage(label) ASM_NL \
.type label SYM_T_OBJECT ASM_NL \
label: \
SYM_END(name, SYM_T_OBJECT)
#endif
/* SYM_DATA -- start+end wrapper around simple global data */
#ifndef SYM_DATA
#define SYM_DATA(name, data...) \
SYM_DATA_START(name) ASM_NL \
data ASM_NL \
SYM_DATA_END(name)
#endif
/* SYM_DATA_LOCAL -- start+end wrapper around simple local data */
#ifndef SYM_DATA_LOCAL
#define SYM_DATA_LOCAL(name, data...) \
SYM_DATA_START_LOCAL(name) ASM_NL \
data ASM_NL \
SYM_DATA_END(name)
#endif
#endif /* __ASSEMBLY__ */
#endif /* _LINUX_LINKAGE_H */
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