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sysdep.h

/* Copyright (C) 2001,02,03 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifndef _LINUX_X86_64_SYSDEP_H
#define _LINUX_X86_64_SYSDEP_H 1

/* There is some commonality.  */
#include <sysdeps/unix/x86_64/sysdep.h>
#include <bp-sym.h>
#include <bp-asm.h>
#include <tls.h>

#ifdef IS_IN_rtld
# include <dl-sysdep.h>       /* Defines RTLD_PRIVATE_ERRNO.  */
#endif

/* For Linux we can use the system call table in the header file
      /usr/include/asm/unistd.h
   of the kernel.  But these symbols do not follow the SYS_* syntax
   so we have to redefine the `SYS_ify' macro here.  */
#undef SYS_ify
#define SYS_ify(syscall_name) __NR_##syscall_name

/* This is a kludge to make syscalls.list find these under the names
   pread and pwrite, since some kernel headers define those names
   and some define the *64 names for the same system calls.  */
#if !defined __NR_pread && defined __NR_pread64
# define __NR_pread __NR_pread64
#endif
#if !defined __NR_pwrite && defined __NR_pwrite64
# define __NR_pwrite __NR_pwrite64
#endif

#ifdef __ASSEMBLER__

/* Linux uses a negative return value to indicate syscall errors,
   unlike most Unices, which use the condition codes' carry flag.

   Since version 2.1 the return value of a system call might be
   negative even if the call succeeded.    E.g., the `lseek' system call
   might return a large offset.      Therefore we must not anymore test
   for < 0, but test for a real error by making sure the value in %eax
   is a real error number.  Linus said he will make sure the no syscall
   returns a value in -1 .. -4095 as a valid result so we can savely
   test with -4095.  */

/* We don't want the label for the error handle to be global when we define
   it here.  */
#ifdef PIC
# define SYSCALL_ERROR_LABEL 0f
#else
# define SYSCALL_ERROR_LABEL syscall_error
#endif

#undef      PSEUDO
#define     PSEUDO(name, syscall_name, args)                            \
  .text;                                                    \
  ENTRY (name)                                                    \
    DO_CALL (syscall_name, args);                                 \
    cmpq $-4095, %rax;                                            \
    jae SYSCALL_ERROR_LABEL;                                      \
  L(pseudo_end):

#undef      PSEUDO_END
#define     PSEUDO_END(name)                                      \
  SYSCALL_ERROR_HANDLER                                           \
  END (name)

#ifndef PIC
#define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.S is used.  */
#elif RTLD_PRIVATE_ERRNO
# define SYSCALL_ERROR_HANDLER                  \
0:                                  \
  leaq errno(%rip), %rcx;                 \
  xorq %rdx, %rdx;                        \
  subq %rax, %rdx;                        \
  movl %edx, (%rcx);                      \
  orq $-1, %rax;                    \
  jmp L(pseudo_end);
#elif USE___THREAD
# ifndef NOT_IN_libc
#  define SYSCALL_ERROR_ERRNO __libc_errno
# else
#  define SYSCALL_ERROR_ERRNO errno
# endif
# define SYSCALL_ERROR_HANDLER                  \
0:                                  \
  movq SYSCALL_ERROR_ERRNO@GOTTPOFF(%rip), %rcx;\
  xorq %rdx, %rdx;                        \
  subq %rax, %rdx;                        \
  movl %edx, %fs:(%rcx);                  \
  orq $-1, %rax;                    \
  jmp L(pseudo_end);
#elif defined _LIBC_REENTRANT
/* Store (- %rax) into errno through the GOT.
   Note that errno occupies only 4 bytes.  */
# define SYSCALL_ERROR_HANDLER                  \
0:                                  \
  xorq %rdx, %rdx;                        \
  subq %rax, %rdx;                        \
  pushq %rdx                              \
  PUSH_ERRNO_LOCATION_RETURN;             \
  call BP_SYM (__errno_location)@PLT;           \
  POP_ERRNO_LOCATION_RETURN;              \
  popq %rdx;                              \
  movl %edx, (%rax);                      \
  orq $-1, %rax;                    \
  jmp L(pseudo_end);

/* A quick note: it is assumed that the call to `__errno_location' does
   not modify the stack!  */
#else /* Not _LIBC_REENTRANT.  */
# define SYSCALL_ERROR_HANDLER                  \
0:movq errno@GOTPCREL(%RIP), %rcx;        \
  xorq %rdx, %rdx;                        \
  subq %rax, %rdx;                        \
  movl %edx, (%rcx);                      \
  orq $-1, %rax;                    \
  jmp L(pseudo_end);
#endif      /* PIC */

/* Linux/x86-64 takes system call arguments in registers:

    Register setup:
    system call number  rax
    arg 1         rdi
    arg 2         rsi
    arg 3         rdx
    arg 4         rcx
    arg 5         r8
    arg 6         r9

    return address from
    syscall       rcx
    additionally clobered: r12-r15,rbx,rbp
    eflags from syscall r11

    The compiler is going to form a call by coming here, through PSEUDO, with arguments:

      syscall number    in the DO_CALL macro
      arg 1       rdi
      arg 2       rsi
      arg 3       rdx
      arg 4       r10
      arg 5       r8
      arg 6       r9

     We have to take care that the stack is alignedto 16 bytes.    When
     called the stack is not aligned since the return address has just
     been pushed.

     Syscalls of more than 6 arguments are not supported.  */

#undef      DO_CALL
#define DO_CALL(syscall_name, args)       \
    DOARGS_##args                   \
    movq $SYS_ify (syscall_name), %rax;         \
    syscall;

#define DOARGS_0 /* nothing */
#define DOARGS_1 /* nothing */
#define DOARGS_2 /* nothing */
#define DOARGS_3 /* nothing */
#define DOARGS_4 movq %rcx, %r10;
#define DOARGS_5 DOARGS_4
#define DOARGS_6 DOARGS_5

#else /* !__ASSEMBLER__ */
/* Define a macro which expands inline into the wrapper code for a system
   call.  */
#undef INLINE_SYSCALL
#define INLINE_SYSCALL(name, nr, args...) \
  ({                                                        \
    unsigned long resultvar = INTERNAL_SYSCALL (name, , nr, args);            \
    if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (resultvar, ), 0))         \
      {                                                           \
      __set_errno (INTERNAL_SYSCALL_ERRNO (resultvar, ));               \
      resultvar = (unsigned long) -1;                                   \
      }                                                           \
    (long) resultvar; })

#undef INTERNAL_SYSCALL_DECL
#define INTERNAL_SYSCALL_DECL(err) do { } while (0)

#undef INTERNAL_SYSCALL
#define INTERNAL_SYSCALL(name, err, nr, args...) \
  ({                                                        \
    unsigned long resultvar;                                      \
    LOAD_ARGS_##nr (args)                                         \
    asm volatile (                                                \
    "movq %1, %%rax\n\t"                                          \
    "syscall\n\t"                                           \
    : "=a" (resultvar)                                            \
    : "i" (__NR_##name) ASM_ARGS_##nr : "memory", "cc", "r11", "cx");         \
    (long) resultvar; })

#undef INTERNAL_SYSCALL_ERROR_P
#define INTERNAL_SYSCALL_ERROR_P(val, err) \
  ((unsigned long) (val) >= -4095L)

#undef INTERNAL_SYSCALL_ERRNO
#define INTERNAL_SYSCALL_ERRNO(val, err)  (-(val))

#define LOAD_ARGS_0()
#define ASM_ARGS_0

#define LOAD_ARGS_1(a1)                         \
  register long int _a1 asm ("rdi") = (long) (a1);    \
  LOAD_ARGS_0 ()
#define ASM_ARGS_1      ASM_ARGS_0, "r" (_a1)

#define LOAD_ARGS_2(a1, a2)                     \
  register long int _a2 asm ("rsi") = (long) (a2);    \
  LOAD_ARGS_1 (a1)
#define ASM_ARGS_2      ASM_ARGS_1, "r" (_a2)

#define LOAD_ARGS_3(a1, a2, a3)                       \
  register long int _a3 asm ("rdx") = (long) (a3);    \
  LOAD_ARGS_2 (a1, a2)
#define ASM_ARGS_3      ASM_ARGS_2, "r" (_a3)

#define LOAD_ARGS_4(a1, a2, a3, a4)             \
  register long int _a4 asm ("r10") = (long) (a4);    \
  LOAD_ARGS_3 (a1, a2, a3)
#define ASM_ARGS_4      ASM_ARGS_3, "r" (_a4)

#define LOAD_ARGS_5(a1, a2, a3, a4, a5)               \
  register long int _a5 asm ("r8") = (long) (a5);     \
  LOAD_ARGS_4 (a1, a2, a3, a4)
#define ASM_ARGS_5      ASM_ARGS_4, "r" (_a5)

#define LOAD_ARGS_6(a1, a2, a3, a4, a5, a6)           \
  register long int _a6 asm ("r9") = (long) (a6);     \
  LOAD_ARGS_5 (a1, a2, a3, a4, a5)
#define ASM_ARGS_6      ASM_ARGS_5, "r" (_a6)

#endif      /* __ASSEMBLER__ */

#endif /* linux/x86_64/sysdep.h */

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