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linux_dsm_epyc7002/include/linux/linkage.h
Nick Desaulniers 4c973f7507 x86/entry: Emit a symbol for register restoring thunk 
commit 5e6dca82bcaa49348f9e5fcb48df4881f6d6c4ae upstream.

Arnd found a randconfig that produces the warning:

  arch/x86/entry/thunk_64.o: warning: objtool: missing symbol for insn at
  offset 0x3e

when building with LLVM_IAS=1 (Clang's integrated assembler). Josh
notes:

  With the LLVM assembler not generating section symbols, objtool has no
  way to reference this code when it generates ORC unwinder entries,
  because this code is outside of any ELF function.

  The limitation now being imposed by objtool 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.

Fangrui notes that this optimization is helpful for reducing image size
when compiling with -ffunction-sections and -fdata-sections. I have
observed on the order of tens of thousands of symbols for the kernel
images built with those flags.

A patch has been authored against GNU binutils to match this behavior
of not generating unused section symbols ([1]), so this will
also become a problem for users of GNU binutils once they upgrade to 2.36.

Omit the .L prefix on a label so that the assembler will emit an entry
into the symbol table for the label, with STB_LOCAL binding. This
enables objtool to generate proper unwind info here with LLVM_IAS=1 or
GNU binutils 2.36+.

 [ bp: Massage commit message. ]

Reported-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Suggested-by: Borislav Petkov <bp@alien8.de>
Suggested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20210112194625.4181814-1-ndesaulniers@google.com
Link: https://github.com/ClangBuiltLinux/linux/issues/1209
Link: https://reviews.llvm.org/D93783
Link: https://sourceware.org/binutils/docs/as/Symbol-Names.html
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1408485ce69f844dcd7ded093a8 [1]
Cc: Chris Clayton <chris2553@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-02-03 23:28:40 +01:00

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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 .align 4,0x90
#define __ALIGN_STR ".align 4,0x90"
#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 \
.size name, .-name
#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_LOCAL_ALIAS -- use where there are two local names for one
* function
*/
#ifndef SYM_FUNC_START_LOCAL_ALIAS
#define SYM_FUNC_START_LOCAL_ALIAS(name) \
SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)
#endif
/*
* SYM_FUNC_START_ALIAS -- use where there are two global names for one
* function
*/
#ifndef SYM_FUNC_START_ALIAS
#define SYM_FUNC_START_ALIAS(name) \
SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)
#endif
/* SYM_FUNC_START -- use for global functions */
#ifndef SYM_FUNC_START
/*
* The same as SYM_FUNC_START_ALIAS, but we will need to distinguish these two
* later.
*/
#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
/* the same as SYM_FUNC_START_LOCAL_ALIAS, see comment near SYM_FUNC_START */
#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_ALIAS -- the end of LOCAL_ALIASed or ALIASed function */
#ifndef SYM_FUNC_END_ALIAS
#define SYM_FUNC_END_ALIAS(name) \
SYM_END(name, SYM_T_FUNC)
#endif
/*
* SYM_FUNC_END -- the end of SYM_FUNC_START_LOCAL, SYM_FUNC_START,
* SYM_FUNC_START_WEAK, ...
*/
#ifndef SYM_FUNC_END
/* the same as SYM_FUNC_END_ALIAS, see comment near SYM_FUNC_START */
#define SYM_FUNC_END(name) \
SYM_END(name, SYM_T_FUNC)
#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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