[thirdparty/glibc.git] / sysdeps / unix / sysv / linux / i386 / sysdep.h

/* Copyright (C) 1992, 93, 95, 96 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper, <drepper@gnu.ai.mit.edu>, August 1995.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

/* There is some commonality.  */
#include <sysdeps/unix/i386/sysdep.h>

/* 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
#ifdef __STDC__
# define SYS_ify(syscall_name)	__NR_##syscall_name
#else
# define SYS_ify(syscall_name)	__NR_/**/syscall_name
#endif


#ifdef ASSEMBLER

/* Linux uses a negative return value to indicate syscall errors, unlike
   most Unices, which use the condition codes' carry flag.  */
#undef	PSEUDO
#define	PSEUDO(name, syscall_name, args)				      \
  .text;								      \
  SYSCALL_ERROR_HANDLER							      \
  ENTRY (name)								      \
    DO_CALL (args, syscall_name);					      \
    testl %eax, %eax;							      \
    jl syscall_error;

#ifndef	PIC
#define SYSCALL_ERROR_HANDLER	/* Nothing here; code in sysdep.S is used.  */
#else
/* Store (- %eax) into errno through the GOT.  */
#define SYSCALL_ERROR_HANDLER						      \
syscall_error:								      \
  call 0f;								      \
0:popl %ecx;								      \
  negl %eax;								      \
  addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ecx;				      \
  movl errno@GOT(%ecx), %ecx;						      \
  movl %eax, (%ecx);							      \
  movl $-1, %eax;							      \
  ret;
#endif

/* Linux takes system call arguments in registers:

	syscall number	%eax	     call-clobbered
	arg 1		%ebx	     call-saved
	arg 2		%ecx	     call-clobbered
	arg 3		%edx	     call-clobbered
	arg 4		%esi	     call-saved
	arg 5		%edi	     call-saved

   The stack layout upon entering the function is:

	20(%esp)	Arg# 5
	16(%esp)	Arg# 4
	12(%esp)	Arg# 3
	 8(%esp)	Arg# 2
	 4(%esp)	Arg# 1
	  (%esp)	Return address

   (Of course a function with say 3 arguments does not have entries for
   arguments 4 and 5.)

   The following code tries hard to be optimal.  A general assuption
   (which is true according to the data books I have) is that

	2 * xchg	is more expensive than	pushl + movl + popl

   Beside this a neat trick is used.  The calling conventions for Linux
   tell that among the registers used for parameters %ecx and %edx need
   not be saved.  Beside this we may clobber this registers even when
   they are not used for parameter passing.

   As a result one can see below that we save the content of the %ebx
   register in the %edx register when we have less than 3 arguments
   (2 * movl is less expensive than pushl + popl).

   Second unlike for the other registers we don't save the content of
   %ecx and %edx when we have than 1 and 2 registers resp.

   The code below might look a bit long but we have to take care for
   the pipelined processors (i586 and up).  Here the `pushl' and `popl'
   instructions are marked as NP (not pairable) but the exception is
   two consecutive of these instruction.  This gives no penalty on
   i386 and i486 processors though.  */

#undef	DO_CALL
#define DO_CALL(args, syscall_name)			      		      \
    PUSHARGS_##args							      \
    DOARGS_##args							      \
    movl $SYS_ify (syscall_name), %eax;					      \
    int $0x80								      \
    POPARGS_##args

#define PUSHARGS_0	/* No arguments to push.  */
#define	DOARGS_0	/* No arguments to frob.  */
#define	POPARGS_0	/* No arguments to pop.  */
#define	_PUSHARGS_0	/* No arguments to push.  */
#define _DOARGS_0(n)	/* No arguments to frob.  */
#define	_POPARGS_0	/* No arguments to pop.  */

#define PUSHARGS_1	movl %ebx, %edx; PUSHARGS_0
#define	DOARGS_1	_DOARGS_1 (4)
#define	POPARGS_1	POPARGS_0; movl %edx, %ebx
#define	_PUSHARGS_1	pushl %ebx; _PUSHARGS_0
#define _DOARGS_1(n)	movl n(%esp), %ebx; _DOARGS_0(n-4)
#define	_POPARGS_1	_POPARGS_0; popl %ebx

#define PUSHARGS_2	PUSHARGS_1
#define	DOARGS_2	_DOARGS_2 (8)
#define	POPARGS_2	POPARGS_1
#define _PUSHARGS_2	_PUSHARGS_1
#define	_DOARGS_2(n)	movl n(%esp), %ecx; _DOARGS_1 (n-4)
#define	_POPARGS_2	_POPARGS_1

#define PUSHARGS_3	_PUSHARGS_2
#define DOARGS_3	_DOARGS_3 (16)
#define POPARGS_3	_POPARGS_3
#define _PUSHARGS_3	_PUSHARGS_2
#define _DOARGS_3(n)	movl n(%esp), %edx; _DOARGS_2 (n-4)
#define _POPARGS_3	_POPARGS_2

#define PUSHARGS_4	_PUSHARGS_4
#define DOARGS_4	_DOARGS_4 (24)
#define POPARGS_4	_POPARGS_4
#define _PUSHARGS_4	pushl %esi; _PUSHARGS_3
#define _DOARGS_4(n)	movl n(%esp), %esi; _DOARGS_3 (n-4)
#define _POPARGS_4	_POPARGS_3; popl %esi

#define PUSHARGS_5	_PUSHARGS_5
#define DOARGS_5	_DOARGS_5 (32)
#define POPARGS_5	_POPARGS_5
#define _PUSHARGS_5	pushl %edi; _PUSHARGS_4
#define _DOARGS_5(n)	movl n(%esp), %edi; _DOARGS_4 (n-4)
#define _POPARGS_5	_POPARGS_4; popl %edi

#endif	/* ASSEMBLER */
Commit	Line	Data
a182affd	1	/* Copyright (C) 1992, 93, 95, 96 Free Software Foundation, Inc.
d2f5be2a UD	2	This file is part of the GNU C Library.
	3	Contributed by Ulrich Drepper, <drepper@gnu.ai.mit.edu>, August 1995.
	4
	5	The GNU C Library is free software; you can redistribute it and/or
	6	modify it under the terms of the GNU Library General Public License as
	7	published by the Free Software Foundation; either version 2 of the
	8	License, or (at your option) any later version.
	9
	10	The GNU C Library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	Library General Public License for more details.
	14
	15	You should have received a copy of the GNU Library General Public
	16	License along with the GNU C Library; see the file COPYING.LIB. If
	17	not, write to the Free Software Foundation, Inc., 675 Mass Ave,
	18	Cambridge, MA 02139, USA. */
	19
d2f5be2a UD	20	/* There is some commonality. */
	21	#include <sysdeps/unix/i386/sysdep.h>
	22
	23	/* For Linux we can use the system call table in the header file
	24	/usr/include/asm/unistd.h
	25	of the kernel. But these symbols do not follow the SYS_* syntax
	26	so we have to redefine the `SYS_ify' macro here. */
	27	#undef SYS_ify
	28	#ifdef __STDC__
	29	# define SYS_ify(syscall_name) __NR_##syscall_name
	30	#else
	31	# define SYS_ify(syscall_name) __NR_/**/syscall_name
	32	#endif
	33
	34
	35	#ifdef ASSEMBLER
	36
	37	/* Linux uses a negative return value to indicate syscall errors, unlike
	38	most Unices, which use the condition codes' carry flag. */
	39	#undef PSEUDO
	40	#define PSEUDO(name, syscall_name, args) \
	41	.text; \
03a75825	42	SYSCALL_ERROR_HANDLER \
d2f5be2a	43	ENTRY (name) \
c14e4c32	44	DO_CALL (args, syscall_name); \
d2f5be2a	45	testl %eax, %eax; \
03a75825	46	jl syscall_error;
d2f5be2a	47
03a75825 RM	48	#ifndef PIC
	49	#define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.S is used. */
	50	#else
	51	/* Store (- %eax) into errno through the GOT. */
	52	#define SYSCALL_ERROR_HANDLER \
	53	syscall_error: \
	54	call 0f; \
	55	0:popl %ecx; \
	56	negl %eax; \
	57	addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ecx; \
	58	movl errno@GOT(%ecx), %ecx; \
	59	movl %eax, (%ecx); \
	60	movl $-1, %eax; \
c14e4c32	61	ret;
03a75825 RM	62	#endif
03a75825 RM	63
d2f5be2a UD	64	/* Linux takes system call arguments in registers:
	65
	66	syscall number %eax call-clobbered
	67	arg 1 %ebx call-saved
	68	arg 2 %ecx call-clobbered
	69	arg 3 %edx call-clobbered
	70	arg 4 %esi call-saved
	71	arg 5 %edi call-saved
	72
	73	The stack layout upon entering the function is:
	74
	75	20(%esp) Arg# 5
	76	16(%esp) Arg# 4
	77	12(%esp) Arg# 3
	78	8(%esp) Arg# 2
	79	4(%esp) Arg# 1
	80	(%esp) Return address
	81
	82	(Of course a function with say 3 arguments does not have entries for
	83	arguments 4 and 5.)
	84
	85	The following code tries hard to be optimal. A general assuption
03a75825	86	(which is true according to the data books I have) is that
d2f5be2a UD	87
	88	2 * xchg is more expensive than pushl + movl + popl
	89
	90	Beside this a neat trick is used. The calling conventions for Linux
	91	tell that among the registers used for parameters %ecx and %edx need
	92	not be saved. Beside this we may clobber this registers even when
	93	they are not used for parameter passing.
	94
	95	As a result one can see below that we save the content of the %ebx
	96	register in the %edx register when we have less than 3 arguments
	97	(2 * movl is less expensive than pushl + popl).
	98
	99	Second unlike for the other registers we don't save the content of
8f5ca04b RM	100	%ecx and %edx when we have than 1 and 2 registers resp.
	101
	102	The code below might look a bit long but we have to take care for
	103	the pipelined processors (i586 and up). Here the `pushl' and `popl'
	104	instructions are marked as NP (not pairable) but the exception is
	105	two consecutive of these instruction. This gives no penalty on
	106	i386 and i486 processors though. */
d2f5be2a UD	107
d2f5be2a UD	108	#undef DO_CALL
c14e4c32	109	#define DO_CALL(args, syscall_name) \
8f5ca04b	110	PUSHARGS_##args \
d2f5be2a	111	DOARGS_##args \
c14e4c32	112	movl $SYS_ify (syscall_name), %eax; \
8f5ca04b RM	113	int $0x80 \
8f5ca04b RM	114	POPARGS_##args
d2f5be2a	115
8f5ca04b	116	#define PUSHARGS_0 /* No arguments to push. */
d2f5be2a	117	#define DOARGS_0 /* No arguments to frob. */
8f5ca04b RM	118	#define POPARGS_0 /* No arguments to pop. */
	119	#define _PUSHARGS_0 /* No arguments to push. */
	120	#define _DOARGS_0(n) /* No arguments to frob. */
	121	#define _POPARGS_0 /* No arguments to pop. */
	122
	123	#define PUSHARGS_1 movl %ebx, %edx; PUSHARGS_0
	124	#define DOARGS_1 _DOARGS_1 (4)
	125	#define POPARGS_1 POPARGS_0; movl %edx, %ebx
	126	#define _PUSHARGS_1 pushl %ebx; _PUSHARGS_0
	127	#define _DOARGS_1(n) movl n(%esp), %ebx; _DOARGS_0(n-4)
	128	#define _POPARGS_1 _POPARGS_0; popl %ebx
	129
	130	#define PUSHARGS_2 PUSHARGS_1
	131	#define DOARGS_2 _DOARGS_2 (8)
	132	#define POPARGS_2 POPARGS_1
	133	#define _PUSHARGS_2 _PUSHARGS_1
d2f5be2a	134	#define _DOARGS_2(n) movl n(%esp), %ecx; _DOARGS_1 (n-4)
8f5ca04b	135	#define _POPARGS_2 _POPARGS_1
d2f5be2a	136
8f5ca04b RM	137	#define PUSHARGS_3 _PUSHARGS_2
	138	#define DOARGS_3 _DOARGS_3 (16)
	139	#define POPARGS_3 _POPARGS_3
	140	#define _PUSHARGS_3 _PUSHARGS_2
d2f5be2a	141	#define _DOARGS_3(n) movl n(%esp), %edx; _DOARGS_2 (n-4)
8f5ca04b RM	142	#define _POPARGS_3 _POPARGS_2
	143
	144	#define PUSHARGS_4 _PUSHARGS_4
	145	#define DOARGS_4 _DOARGS_4 (24)
	146	#define POPARGS_4 _POPARGS_4
	147	#define _PUSHARGS_4 pushl %esi; _PUSHARGS_3
	148	#define _DOARGS_4(n) movl n(%esp), %esi; _DOARGS_3 (n-4)
	149	#define _POPARGS_4 _POPARGS_3; popl %esi
	150
	151	#define PUSHARGS_5 _PUSHARGS_5
	152	#define DOARGS_5 _DOARGS_5 (32)
	153	#define POPARGS_5 _POPARGS_5
	154	#define _PUSHARGS_5 pushl %edi; _PUSHARGS_4
	155	#define _DOARGS_5(n) movl n(%esp), %edi; _DOARGS_4 (n-4)
	156	#define _POPARGS_5 _POPARGS_4; popl %edi
d2f5be2a UD	157
d2f5be2a UD	158	#endif /* ASSEMBLER */