sysdeps/unix/sysv/linux/x86_64/sysdep.h

   1 /* Copyright (C) 2001,02,03 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #ifndef _LINUX_X86_64_SYSDEP_H
  20 #define _LINUX_X86_64_SYSDEP_H 1
  21
  22 /* There is some commonality.  */
  23 #include <sysdeps/unix/x86_64/sysdep.h>
  24 #include <bp-sym.h>
  25 #include <bp-asm.h>
  26 #include <tls.h>
  27
  28 #ifdef IS_IN_rtld
  29 # include <dl-sysdep.h>         /* Defines RTLD_PRIVATE_ERRNO.  */
  30 #endif
  31
  32 /* For Linux we can use the system call table in the header file
  33         /usr/include/asm/unistd.h
  34    of the kernel.  But these symbols do not follow the SYS_* syntax
  35    so we have to redefine the `SYS_ify' macro here.  */
  36 #undef SYS_ify
  37 #define SYS_ify(syscall_name)   __NR_##syscall_name
  38
  39 /* This is a kludge to make syscalls.list find these under the names
  40    pread and pwrite, since some kernel headers define those names
  41    and some define the *64 names for the same system calls.  */
  42 #if !defined __NR_pread && defined __NR_pread64
  43 # define __NR_pread __NR_pread64
  44 #endif
  45 #if !defined __NR_pwrite && defined __NR_pwrite64
  46 # define __NR_pwrite __NR_pwrite64
  47 #endif
  48
  49 #ifdef __ASSEMBLER__
  50
  51 /* Linux uses a negative return value to indicate syscall errors,
  52    unlike most Unices, which use the condition codes' carry flag.
  53
  54    Since version 2.1 the return value of a system call might be
  55    negative even if the call succeeded.  E.g., the `lseek' system call
  56    might return a large offset.  Therefore we must not anymore test
  57    for < 0, but test for a real error by making sure the value in %eax
  58    is a real error number.  Linus said he will make sure the no syscall
  59    returns a value in -1 .. -4095 as a valid result so we can savely
  60    test with -4095.  */
  61
  62 /* We don't want the label for the error handle to be global when we define
  63    it here.  */
  64 #ifdef PIC
  65 # define SYSCALL_ERROR_LABEL 0f
  66 #else
  67 # define SYSCALL_ERROR_LABEL syscall_error
  68 #endif
  69
  70 #undef  PSEUDO
  71 #define PSEUDO(name, syscall_name, args)                                      \
  72   .text;                                                                      \
  73   ENTRY (name)                                                                \
  74     DO_CALL (syscall_name, args);                                             \
  75     cmpq $-4095, %rax;                                                        \
  76     jae SYSCALL_ERROR_LABEL;                                                  \
  77   L(pseudo_end):
  78
  79 #undef  PSEUDO_END
  80 #define PSEUDO_END(name)                                                      \
  81   SYSCALL_ERROR_HANDLER                                                       \
  82   END (name)
  83
  84 #ifndef PIC
  85 #define SYSCALL_ERROR_HANDLER   /* Nothing here; code in sysdep.S is used.  */
  86 #elif RTLD_PRIVATE_ERRNO
  87 # define SYSCALL_ERROR_HANDLER                  \
  88 0:                                              \
  89   leaq errno(%rip), %rcx;                       \
  90   xorq %rdx, %rdx;                              \
  91   subq %rax, %rdx;                              \
  92   movl %edx, (%rcx);                            \
  93   orq $-1, %rax;                                \
  94   jmp L(pseudo_end);
  95 #elif USE___THREAD
  96 # ifndef NOT_IN_libc
  97 #  define SYSCALL_ERROR_ERRNO __libc_errno
  98 # else
  99 #  define SYSCALL_ERROR_ERRNO errno
 100 # endif
 101 # define SYSCALL_ERROR_HANDLER                  \
 102 0:                                              \
 103   movq SYSCALL_ERROR_ERRNO@GOTTPOFF(%rip), %rcx;\
 104   xorq %rdx, %rdx;                              \
 105   subq %rax, %rdx;                              \
 106   movl %edx, %fs:(%rcx);                        \
 107   orq $-1, %rax;                                \
 108   jmp L(pseudo_end);
 109 #elif defined _LIBC_REENTRANT
 110 /* Store (- %rax) into errno through the GOT.
 111    Note that errno occupies only 4 bytes.  */
 112 # define SYSCALL_ERROR_HANDLER                  \
 113 0:                                              \
 114   xorq %rdx, %rdx;                              \
 115   subq %rax, %rdx;                              \
 116   pushq %rdx                                    \
 117   PUSH_ERRNO_LOCATION_RETURN;                   \
 118   call BP_SYM (__errno_location)@PLT;           \
 119   POP_ERRNO_LOCATION_RETURN;                    \
 120   popq %rdx;                                    \
 121   movl %edx, (%rax);                            \
 122   orq $-1, %rax;                                \
 123   jmp L(pseudo_end);
 124
 125 /* A quick note: it is assumed that the call to `__errno_location' does
 126    not modify the stack!  */
 127 #else /* Not _LIBC_REENTRANT.  */
 128 # define SYSCALL_ERROR_HANDLER                  \
 129 0:movq errno@GOTPCREL(%RIP), %rcx;              \
 130   xorq %rdx, %rdx;                              \
 131   subq %rax, %rdx;                              \
 132   movl %edx, (%rcx);                            \
 133   orq $-1, %rax;                                \
 134   jmp L(pseudo_end);
 135 #endif  /* PIC */
 136
 137 /* The Linux/x86-64 kernel expects the system call parameters in
 138    registers according to the following table:
 139
 140     syscall number      rax
 141     arg 1               rdi
 142     arg 2               rsi
 143     arg 3               rdx
 144     arg 4               r10
 145     arg 5               r8
 146     arg 6               r9
 147
 148     The Linux kernel uses and destroys internally these registers:
 149     return address from
 150     syscall             rcx
 151     additionally clobered: r12-r15,rbx,rbp
 152     eflags from syscall r11
 153
 154     Normal function call, including calls to the system call stub
 155     functions in the libc, get the first six parameters passed in
 156     registers and the seventh parameter and later on the stack.  The
 157     register use is as follows:
 158
 159      system call number in the DO_CALL macro
 160      arg 1              rdi
 161      arg 2              rsi
 162      arg 3              rdx
 163      arg 4              rcx
 164      arg 5              r8
 165      arg 6              r9
 166
 167     We have to take care that the stack is aligned to 16 bytes.  When
 168     called the stack is not aligned since the return address has just
 169     been pushed.
 170
 171
 172     Syscalls of more than 6 arguments are not supported.  */
 173
 174 #undef  DO_CALL
 175 #define DO_CALL(syscall_name, args)             \
 176     DOARGS_##args                               \
 177     movq $SYS_ify (syscall_name), %rax;         \
 178     syscall;
 179
 180 #define DOARGS_0 /* nothing */
 181 #define DOARGS_1 /* nothing */
 182 #define DOARGS_2 /* nothing */
 183 #define DOARGS_3 /* nothing */
 184 #define DOARGS_4 movq %rcx, %r10;
 185 #define DOARGS_5 DOARGS_4
 186 #define DOARGS_6 DOARGS_5
 187
 188 #else   /* !__ASSEMBLER__ */
 189 /* Define a macro which expands inline into the wrapper code for a system
 190    call.  */
 191 #undef INLINE_SYSCALL
 192 #define INLINE_SYSCALL(name, nr, args...) \
 193   ({                                                                          \
 194     unsigned long resultvar = INTERNAL_SYSCALL (name, , nr, args);            \
 195     if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (resultvar, ), 0))         \
 196       {                                                                       \
 197         __set_errno (INTERNAL_SYSCALL_ERRNO (resultvar, ));                   \
 198         resultvar = (unsigned long) -1;                                       \
 199       }                                                                       \
 200     (long) resultvar; })
 201
 202 #undef INTERNAL_SYSCALL_DECL
 203 #define INTERNAL_SYSCALL_DECL(err) do { } while (0)
 204
 205 #undef INTERNAL_SYSCALL
 206 #define INTERNAL_SYSCALL(name, err, nr, args...) \
 207   ({                                                                          \
 208     unsigned long resultvar;                                                  \
 209     LOAD_ARGS_##nr (args)                                                     \
 210     asm volatile (                                                            \
 211     "movq %1, %%rax\n\t"                                                      \
 212     "syscall\n\t"                                                             \
 213     : "=a" (resultvar)                                                        \
 214     : "i" (__NR_##name) ASM_ARGS_##nr : "memory", "cc", "r11", "cx");         \
 215     (long) resultvar; })
 216
 217 #undef INTERNAL_SYSCALL_ERROR_P
 218 #define INTERNAL_SYSCALL_ERROR_P(val, err) \
 219   ((unsigned long) (val) >= -4095L)
 220
 221 #undef INTERNAL_SYSCALL_ERRNO
 222 #define INTERNAL_SYSCALL_ERRNO(val, err)        (-(val))
 223
 224 #define LOAD_ARGS_0()
 225 #define ASM_ARGS_0
 226
 227 #define LOAD_ARGS_1(a1)                                 \
 228   register long int _a1 asm ("rdi") = (long) (a1);      \
 229   LOAD_ARGS_0 ()
 230 #define ASM_ARGS_1      ASM_ARGS_0, "r" (_a1)
 231
 232 #define LOAD_ARGS_2(a1, a2)                             \
 233   register long int _a2 asm ("rsi") = (long) (a2);      \
 234   LOAD_ARGS_1 (a1)
 235 #define ASM_ARGS_2      ASM_ARGS_1, "r" (_a2)
 236
 237 #define LOAD_ARGS_3(a1, a2, a3)                         \
 238   register long int _a3 asm ("rdx") = (long) (a3);      \
 239   LOAD_ARGS_2 (a1, a2)
 240 #define ASM_ARGS_3      ASM_ARGS_2, "r" (_a3)
 241
 242 #define LOAD_ARGS_4(a1, a2, a3, a4)                     \
 243   register long int _a4 asm ("r10") = (long) (a4);      \
 244   LOAD_ARGS_3 (a1, a2, a3)
 245 #define ASM_ARGS_4      ASM_ARGS_3, "r" (_a4)
 246
 247 #define LOAD_ARGS_5(a1, a2, a3, a4, a5)                 \
 248   register long int _a5 asm ("r8") = (long) (a5);       \
 249   LOAD_ARGS_4 (a1, a2, a3, a4)
 250 #define ASM_ARGS_5      ASM_ARGS_4, "r" (_a5)
 251
 252 #define LOAD_ARGS_6(a1, a2, a3, a4, a5, a6)             \
 253   register long int _a6 asm ("r9") = (long) (a6);       \
 254   LOAD_ARGS_5 (a1, a2, a3, a4, a5)
 255 #define ASM_ARGS_6      ASM_ARGS_5, "r" (_a6)
 256
 257 #endif  /* __ASSEMBLER__ */
 258
 259 #endif /* linux/x86_64/sysdep.h */