uclibc-ng/libc/sysdeps/linux/x86_64/sysdep.h

/* Copyright (C) 2001-2005, 2007 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, see
   <http://www.gnu.org/licenses/>.  */

#ifndef _LINUX_X86_64_SYSDEP_H
#define _LINUX_X86_64_SYSDEP_H 1

/* There is some commonality.  */
#include <sys/syscall.h>
#include <common/sysdep.h>

#ifdef	__ASSEMBLER__

/* Syntactic details of assembler.  */

/* ELF uses byte-counts for .align, most others use log2 of count of bytes.  */
#define ALIGNARG(log2) 1<<log2
/* For ELF we need the `.type' directive to make shared libs work right.  */
#define ASM_TYPE_DIRECTIVE(name,typearg) .type name,typearg;
#define ASM_SIZE_DIRECTIVE(name) .size name,.-name;

/* In ELF C symbols are asm symbols.  */
#undef	NO_UNDERSCORES
#define NO_UNDERSCORES

/* Define an entry point visible from C.  */
#define	ENTRY(name)							      \
  .globl C_SYMBOL_NAME(name);				      \
  ASM_TYPE_DIRECTIVE (C_SYMBOL_NAME(name),@function)			      \
  .align ALIGNARG(4);							      \
  C_LABEL(name)								      \
  cfi_startproc;

#undef	END
#define END(name)							      \
  cfi_endproc;								      \
  ASM_SIZE_DIRECTIVE(name)

#ifdef	NO_UNDERSCORES
/* Since C identifiers are not normally prefixed with an underscore
   on this system, the asm identifier `syscall_error' intrudes on the
   C name space.  Make sure we use an innocuous name.  */
#define	syscall_error	__syscall_error
#define mcount		_mcount
#endif

#define	PSEUDO(name, syscall_name, args)				      \
lose:									      \
  jmp JUMPTARGET(syscall_error)						      \
  .globl syscall_error;							      \
  ENTRY (name)								      \
  DO_CALL (syscall_name, args);						      \
  jb lose

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

#undef JUMPTARGET
#ifdef __PIC__
#define JUMPTARGET(name)	name##@PLT
#else
#define JUMPTARGET(name)	name
#endif

/* Local label name for asm code. */
#ifndef L
#define L(name)	.L##name
#endif

#endif	/* __ASSEMBLER__ */

/* 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

/* This is to help the old kernel headers where __NR_semtimedop is not
   available.  */
#ifndef __NR_semtimedop
# define __NR_semtimedop 220
#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)

# undef	PSEUDO_NOERRNO
# define PSEUDO_NOERRNO(name, syscall_name, args) \
  .text;								      \
  ENTRY (name)								      \
    DO_CALL (syscall_name, args)

# undef	PSEUDO_END_NOERRNO
# define PSEUDO_END_NOERRNO(name) \
  END (name)

# define ret_NOERRNO ret

# undef	PSEUDO_ERRVAL
# define PSEUDO_ERRVAL(name, syscall_name, args) \
  .text;								      \
  ENTRY (name)								      \
    DO_CALL (syscall_name, args);					      \
    negq %rax

# undef	PSEUDO_END_ERRVAL
# define PSEUDO_END_ERRVAL(name) \
  END (name)

# ifndef __PIC__
#  define SYSCALL_ERROR_HANDLER	/* Nothing here; code in sysdep.S is used.  */
# elif USE___THREAD
#   define SYSCALL_ERROR_ERRNO errno
#  define SYSCALL_ERROR_HANDLER			\
0:						\
  movq SYSCALL_ERROR_ERRNO@GOTTPOFF(%rip), %rcx;\
  xorl %edx, %edx;				\
  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:						\
  xorl %edx, %edx;				\
  subq %rax, %rdx;				\
  pushq %rdx;					\
  cfi_adjust_cfa_offset(8);			\
  call __errno_location@PLT;		\
  popq %rdx;					\
  cfi_adjust_cfa_offset(-8);			\
  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;		\
  xorl %edx, %edx;				\
  subq %rax, %rdx;				\
  movl %edx, (%rcx);				\
  orq $-1, %rax;				\
  jmp L(pseudo_end);
# endif	/* __PIC__ */

/* The Linux/x86-64 kernel expects the system call parameters in
   registers according to the following table:

    syscall number	rax
    arg 1		rdi
    arg 2		rsi
    arg 3		rdx
    arg 4		r10
    arg 5		r8
    arg 6		r9

    The Linux kernel uses and destroys internally these registers:
    return address from
    syscall		rcx
    eflags from syscall	r11

    Normal function call, including calls to the system call stub
    functions in the libc, get the first six parameters passed in
    registers and the seventh parameter and later on the stack.  The
    register use is as follows:

     system call number	in the DO_CALL macro
     arg 1		rdi
     arg 2		rsi
     arg 3		rdx
     arg 4		rcx
     arg 5		r8
     arg 6		r9

    We have to take care that the stack is aligned to 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				\
    movl $SYS_ify (syscall_name), %eax;		\
    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

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