1. 根目录:
2. include
3. asm-generic
4. sections.h

#ifndef _ASM_GENERIC_SECTIONS_H_
#define _ASM_GENERIC_SECTIONS_H_

/* References to section boundaries */

#include <linux/compiler.h>

/*
 * Usage guidelines:
 * _text, _data: architecture specific, don't use them in arch-independent code
 * [_stext, _etext]: contains .text.* sections, may also contain .rodata.*
 *                   and/or .init.* sections
 * [_sdata, _edata]: contains .data.* sections, may also contain .rodata.*
 *                   and/or .init.* sections.
 * [__start_rodata, __end_rodata]: contains .rodata.* sections
 * [__init_begin, __init_end]: contains .init.* sections, but .init.text.*
 *                   may be out of this range on some architectures.
 * [_sinittext, _einittext]: contains .init.text.* sections
 * [__bss_start, __bss_stop]: contains BSS sections
 *
 * Following global variables are optional and may be unavailable on some
 * architectures and/or kernel configurations.
 *	_text, _data
 *	__kprobes_text_start, __kprobes_text_end
 *	__entry_text_start, __entry_text_end
 *	__ctors_start, __ctors_end
 */
extern char _text[], _stext[], _etext[];
extern char _data[], _sdata[], _edata[];
extern char __bss_start[], __bss_stop[];
extern char __init_begin[], __init_end[];
extern char _sinittext[], _einittext[];
extern char _end[];
extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[];
extern char __kprobes_text_start[], __kprobes_text_end[];
extern char __entry_text_start[], __entry_text_end[];
extern char __start_rodata[], __end_rodata[];

/* Start and end of .ctors section - used for constructor calls. */
extern char __ctors_start[], __ctors_end[];

extern __visible const void __nosave_begin, __nosave_end;

/* function descriptor handling (if any).  Override
 * in asm/sections.h */
#ifndef dereference_function_descriptor
#define dereference_function_descriptor(p) (p)
#endif

/* random extra sections (if any).  Override
 * in asm/sections.h */
#ifndef arch_is_kernel_text
static inline int arch_is_kernel_text(unsigned long addr)
{
	return 0;
}
#endif

#ifndef arch_is_kernel_data
static inline int arch_is_kernel_data(unsigned long addr)
{
	return 0;
}
#endif

#endif /* _ASM_GENERIC_SECTIONS_H_ */