syscalls.h

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

#ifndef _BITS_SYSCALLS_H
#define _BITS_SYSCALLS_H
#ifndef _SYSCALL_H
# error "Never use <bits/syscalls.h> directly; include <sys/syscall.h> instead."
#endif

/* This includes the `__NR_<name>' syscall numbers taken from the Linux kernel
 * header files.  It also defines the traditional `SYS_<name>' macros for older
 * programs.  */
#include <bits/sysnum.h>

#ifndef __set_errno
# define __set_errno(val) (*__errno_location ()) = (val)
#endif

/*
   Some of the sneaky macros in the code were taken from 
   glibc-2.2.5/sysdeps/unix/sysv/linux/i386/sysdep.h
*/

#ifndef __ASSEMBLER__

/* We need some help from the assembler to generate optimal code.  We
   define some macros here which later will be used.  */
asm (".L__X'%ebx = 1\n\t"
     ".L__X'%ecx = 2\n\t"
     ".L__X'%edx = 2\n\t"
     ".L__X'%eax = 3\n\t"
     ".L__X'%esi = 3\n\t"
     ".L__X'%edi = 3\n\t"
     ".L__X'%ebp = 3\n\t"
     ".L__X'%esp = 3\n\t"
     ".macro bpushl name reg\n\t"
     ".if 1 - \\name\n\t"
     ".if 2 - \\name\n\t"
     "pushl %ebx\n\t"
     ".else\n\t"
     "xchgl \\reg, %ebx\n\t"
     ".endif\n\t"
     ".endif\n\t"
     ".endm\n\t"
     ".macro bpopl name reg\n\t"
     ".if 1 - \\name\n\t"
     ".if 2 - \\name\n\t"
     "popl %ebx\n\t"
     ".else\n\t"
     "xchgl \\reg, %ebx\n\t"
     ".endif\n\t"
     ".endif\n\t"
     ".endm\n\t"
     ".macro bmovl name reg\n\t"
     ".if 1 - \\name\n\t"
     ".if 2 - \\name\n\t"
     "movl \\reg, %ebx\n\t"
     ".endif\n\t"
     ".endif\n\t"
     ".endm\n\t");


#undef _syscall0
#define _syscall0(type,name) \
type name(void) \
{ \
return (type) (INLINE_SYSCALL(name, 0)); \
}

#undef _syscall1
#define _syscall1(type,name,type1,arg1) \
type name(type1 arg1) \
{ \
return (type) (INLINE_SYSCALL(name, 1, arg1)); \
}

#undef _syscall2
#define _syscall2(type,name,type1,arg1,type2,arg2) \
type name(type1 arg1,type2 arg2) \
{ \
return (type) (INLINE_SYSCALL(name, 2, arg1, arg2)); \
}

#undef _syscall3
#define _syscall3(type,name,type1,arg1,type2,arg2,type3,arg3) \
type name(type1 arg1,type2 arg2,type3 arg3) \
{ \
return (type) (INLINE_SYSCALL(name, 3, arg1, arg2, arg3)); \
}

#undef _syscall4
#define _syscall4(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4) \
type name (type1 arg1, type2 arg2, type3 arg3, type4 arg4) \
{ \
return (type) (INLINE_SYSCALL(name, 4, arg1, arg2, arg3, arg4)); \
} 

#undef _syscall5
#define _syscall5(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4, \
	  type5,arg5) \
type name (type1 arg1,type2 arg2,type3 arg3,type4 arg4,type5 arg5) \
{ \
return (type) (INLINE_SYSCALL(name, 5, arg1, arg2, arg3, arg4, arg5)); \
}

#define INLINE_SYSCALL(name, nr, args...) \
  ({									      \
    unsigned int resultvar;						      \
    asm volatile (							      \
    LOADARGS_##nr							      \
    "movl %1, %%eax\n\t"						      \
    "int $0x80\n\t"							      \
    RESTOREARGS_##nr							      \
    : "=a" (resultvar)							      \
    : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc");		      \
    if (resultvar >= 0xfffff001)					      \
      {									      \
	__set_errno (-resultvar);					      \
	resultvar = 0xffffffff;						      \
      }									      \
    (int) resultvar; })

#define LOADARGS_0
#define LOADARGS_1 \
    "bpushl .L__X'%k2, %k2\n\t"						      \
    "bmovl .L__X'%k2, %k2\n\t"
#define LOADARGS_2	LOADARGS_1
#define LOADARGS_3	LOADARGS_1
#define LOADARGS_4	LOADARGS_1
#define LOADARGS_5	LOADARGS_1

#define RESTOREARGS_0
#define RESTOREARGS_1 \
    "bpopl .L__X'%k2, %k2\n\t"
#define RESTOREARGS_2	RESTOREARGS_1
#define RESTOREARGS_3	RESTOREARGS_1
#define RESTOREARGS_4	RESTOREARGS_1
#define RESTOREARGS_5	RESTOREARGS_1

#define ASMFMT_0()
#define ASMFMT_1(arg1) \
	, "acdSD" (arg1)
#define ASMFMT_2(arg1, arg2) \
	, "adCD" (arg1), "c" (arg2)
#define ASMFMT_3(arg1, arg2, arg3) \
	, "aCD" (arg1), "c" (arg2), "d" (arg3)
#define ASMFMT_4(arg1, arg2, arg3, arg4) \
	, "aD" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
#define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
	, "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)


#endif /* __ASSEMBLER__ */
#endif /* _BITS_SYSCALLS_H */