libc/sysdeps/linux/i386/bits/syscalls.h

   1 #ifndef _BITS_SYSCALLS_H
   2 #define _BITS_SYSCALLS_H
   3
   4 #ifndef _SYSCALL_H
   5 # error "Never use <bits/syscalls.h> directly; include <sys/syscall.h> instead."
   6 #endif
   7
   8 /*
   9  * Some of the sneaky macros in the code were taken from
  10  * glibc-2.2.5/sysdeps/unix/sysv/linux/i386/sysdep.h
  11  */
  12
  13 #ifndef __ASSEMBLER__
  14
  15 #include <errno.h>
  16
  17 #define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
  18 ({ \
  19         register unsigned int resultvar; \
  20         __asm__ __volatile__ ( \
  21                 LOADARGS_##nr                                   \
  22                 "movl   %1, %%eax\n\t"                          \
  23                 "int    $0x80\n\t"                              \
  24                 RESTOREARGS_##nr                                \
  25                 : "=a" (resultvar)                              \
  26                 : "i" (name) ASMFMT_##nr(args) : "memory", "cc" \
  27         ); \
  28         (int) resultvar; \
  29 })
  30
  31
  32 #if 1 /* defined __PIC__ || defined __pic__ */
  33
  34 /* This code avoids pushing/popping ebx as much as possible.
  35  * I think the main reason was that older GCCs had problems
  36  * with proper saving/restoring of ebx if "b" constraint was used,
  37  * which was breaking -fPIC code really badly.
  38  * At least gcc 4.2.x seems to not need these tricks anymore,
  39  * but this code is still useful because it often avoids
  40  * using stack for saving ebx.
  41  * Keeping it unconditionally enabled for now.
  42  */
  43
  44 /* We need some help from the assembler to generate optimal code.
  45  * We define some macros here which later will be used.  */
  46
  47 __asm__ (
  48 #ifdef __DOMULTI__
  49         /* Protect against asm macro redefinition (happens in __DOMULTI__ mode).
  50          * Unfortunately, it ends up visible in .o files. */
  51         ".ifndef _BITS_SYSCALLS_ASM\n\t"
  52         ".set _BITS_SYSCALLS_ASM,1\n\t"
  53 #endif
  54         ".L__X'%ebx = 1\n\t"
  55         ".L__X'%ecx = 2\n\t"
  56         ".L__X'%edx = 2\n\t"
  57         ".L__X'%eax = 3\n\t"
  58         ".L__X'%esi = 3\n\t"
  59         ".L__X'%edi = 3\n\t"
  60         ".L__X'%ebp = 3\n\t"
  61         ".L__X'%esp = 3\n\t"
  62
  63         /* Loading param #1 (ebx) is done by loading it into
  64          * another register, and then performing bpushl+bmovl,
  65          * since we must preserve ebx */
  66
  67         ".macro bpushl name reg\n\t"
  68         ".if 1 - \\name\n\t"    /* if reg!=ebx... */
  69         ".if 2 - \\name\n\t"    /* if reg can't be clobbered... */
  70         "pushl %ebx\n\t"        /* save ebx on stack */
  71         ".else\n\t"
  72         "xchgl \\reg, %ebx\n\t" /* else save ebx in reg, and load reg to ebx */
  73         ".endif\n\t"
  74         ".endif\n\t"
  75         ".endm\n\t"
  76
  77         ".macro bmovl name reg\n\t"
  78         ".if 1 - \\name\n\t"
  79         ".if 2 - \\name\n\t"    /* if reg can't be clobbered... */
  80         "movl \\reg, %ebx\n\t"  /* load reg to ebx */
  81         ".endif\n\t"
  82         ".endif\n\t"
  83         ".endm\n\t"
  84
  85         ".macro bpopl name reg\n\t"
  86         ".if 1 - \\name\n\t"
  87         ".if 2 - \\name\n\t"    /* if reg can't be clobbered... */
  88         "popl %ebx\n\t"         /* restore ebx from stack */
  89         ".else\n\t"
  90         "xchgl \\reg, %ebx\n\t" /* else restore ebx from reg */
  91         ".endif\n\t"
  92         ".endif\n\t"
  93         ".endm\n\t"
  94
  95 #ifdef __DOMULTI__
  96         ".endif\n\t" /* _BITS_SYSCALLS_ASM */
  97 #endif
  98 );
  99
 100 #define LOADARGS_0
 101 #define LOADARGS_1  "bpushl .L__X'%k2, %k2\n\t" "bmovl .L__X'%k2, %k2\n\t"
 102 #define LOADARGS_2  LOADARGS_1
 103 #define LOADARGS_3  LOADARGS_1
 104 #define LOADARGS_4  LOADARGS_1
 105 #define LOADARGS_5  LOADARGS_1
 106 #define LOADARGS_6  LOADARGS_1 "push %%ebp\n\t" "movl %7, %%ebp\n\t"
 107
 108 #define RESTOREARGS_0
 109 #define RESTOREARGS_1  "bpopl .L__X'%k2, %k2\n\t"
 110 #define RESTOREARGS_2  RESTOREARGS_1
 111 #define RESTOREARGS_3  RESTOREARGS_1
 112 #define RESTOREARGS_4  RESTOREARGS_1
 113 #define RESTOREARGS_5  RESTOREARGS_1
 114 #define RESTOREARGS_6  "pop %%ebp\n\t" RESTOREARGS_1
 115
 116 #define ASMFMT_0()
 117 /* "acdSD" constraint would work too, but "SD" would use esi/edi and cause
 118  * them to be pushed/popped by compiler, "a" would use eax and cause ebx
 119  * to be saved/restored on stack, not in register. Narrowing choice down
 120  * to "ecx or edx" results in smaller and faster code: */
 121 #define ASMFMT_1(arg1) \
 122         , "cd" (arg1)
 123 /* Can use "adSD" constraint here: */
 124 #define ASMFMT_2(arg1, arg2) \
 125         , "d" (arg1), "c" (arg2)
 126 /* Can use "aSD" constraint here: */
 127 #define ASMFMT_3(arg1, arg2, arg3) \
 128         , "a" (arg1), "c" (arg2), "d" (arg3)
 129 /* Can use "aD" constraint here: */
 130 #define ASMFMT_4(arg1, arg2, arg3, arg4) \
 131         , "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
 132 #define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
 133         , "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)
 134 #define ASMFMT_6(arg1, arg2, arg3, arg4, arg5, arg6) \
 135         , "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5), "m" (arg6)
 136
 137 #else /* !PIC */
 138
 139 /* Simpler code which just uses "b" constraint to load ebx.
 140  * Seems to work with gc 4.2.x, and generates slightly smaller,
 141  * but slightly slower code. Example (time syscall):
 142  *
 143  * -    8b 4c 24 04            mov    0x4(%esp),%ecx
 144  * -    87 cb                  xchg   %ecx,%ebx
 145  * +    53                     push   %ebx
 146  * +    8b 5c 24 08            mov    0x8(%esp),%ebx
 147  *      b8 0d 00 00 00         mov    $0xd,%eax
 148  *      cd 80                  int    $0x80
 149  * -    87 cb                  xchg   %ecx,%ebx
 150  * +    5b                     pop    %ebx
 151  *      c3                     ret
 152  *
 153  * 2 bytes smaller, but uses stack via "push/pop ebx"
 154  */
 155
 156 #define LOADARGS_0
 157 #define LOADARGS_1
 158 #define LOADARGS_2
 159 #define LOADARGS_3
 160 #define LOADARGS_4
 161 #define LOADARGS_5
 162 #define LOADARGS_6  "push %%ebp\n\t" "movl %7, %%ebp\n\t"
 163
 164 #define RESTOREARGS_0
 165 #define RESTOREARGS_1
 166 #define RESTOREARGS_2
 167 #define RESTOREARGS_3
 168 #define RESTOREARGS_4
 169 #define RESTOREARGS_5
 170 #define RESTOREARGS_6  "pop %%ebp\n\t"
 171
 172 #define ASMFMT_0()
 173 #define ASMFMT_1(arg1) \
 174         , "b" (arg1)
 175 #define ASMFMT_2(arg1, arg2) \
 176         , "b" (arg1), "c" (arg2)
 177 #define ASMFMT_3(arg1, arg2, arg3) \
 178         , "b" (arg1), "c" (arg2), "d" (arg3)
 179 #define ASMFMT_4(arg1, arg2, arg3, arg4) \
 180         , "b" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
 181 #define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
 182         , "b" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)
 183 #define ASMFMT_6(arg1, arg2, arg3, arg4, arg5, arg6) \
 184         , "b" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5), "m" (arg6)
 185
 186 #endif /* !PIC */
 187
 188 #endif /* __ASSEMBLER__ */
 189 #endif /* _BITS_SYSCALLS_H */