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

/* Copyright (C) 1992, 93, 95, 96, 97, 98 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., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#ifndef _LINUX_I386_SYSDEP_H
#define _LINUX_I386_SYSDEP_H 1

/* 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
#define SYS_ify(syscall_name)	__NR_##syscall_name

/* ELF-like local names start with `.L'.  */
#undef L
#define L(name)	.L##name

#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.  */
#undef	PSEUDO
#define	PSEUDO(name, syscall_name, args)				      \
  .text;								      \
  ENTRY (name)								      \
    DO_CALL (args, syscall_name);					      \
    cmpl $-4095, %eax;							      \
    jae syscall_error;							      \
  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.  */
#else
/* Store (- %eax) into errno through the GOT.  */
#ifdef _LIBC_REENTRANT
#define SYSCALL_ERROR_HANDLER						      \
  .type syscall_error,@function;					      \
syscall_error:								      \
  pushl %ebx;								      \
  call 0f;								      \
0:popl %ebx;								      \
  xorl %edx, %edx;							      \
  addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx;				      \
  subl %eax, %edx;							      \
  pushl %edx;								      \
  call __errno_location@PLT;						      \
  popl %ecx;								      \
  popl %ebx;								      \
  movl %ecx, (%eax);							      \
  movl $-1, %eax;							      \
  jmp L(pseudo_end);							      \
  .size syscall_error,.-syscall_error;
/* A quick note: it is assumed that the call to `__errno_location' does
   not modify the stack!  */
#else
#define SYSCALL_ERROR_HANDLER						      \
  .type syscall_error,@function;					      \
syscall_error:								      \
  call 0f;								      \
0:popl %ecx;								      \
  xorl %edx, %edx;							      \
  addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ecx;				      \
  subl %eax, %edx;							      \
  movl errno@GOT(%ecx), %ecx;						      \
  movl %edx, (%ecx);							      \
  movl $-1, %eax;							      \
  jmp L(pseudo_end);							      \
  .size syscall_error,.-syscall_error;
#endif	/* _LIBC_REENTRANT */
#endif	/* PIC */

/* 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 assumption
   (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 more 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 */

#endif /* linux/i386/sysdep.h */
Commit	Line	Data
ae828bc6	1	/* Copyright (C) 1992, 93, 95, 96, 97, 98 Free Software Foundation, Inc.
bfbc5754 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 not,
	17	write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	18	Boston, MA 02111-1307, USA. */
d2f5be2a	19
ec4b0518 UD	20	#ifndef _LINUX_I386_SYSDEP_H
	21	#define _LINUX_I386_SYSDEP_H 1
	22
d2f5be2a UD	23	/* There is some commonality. */
	24	#include <sysdeps/unix/i386/sysdep.h>
	25
	26	/* For Linux we can use the system call table in the header file
	27	/usr/include/asm/unistd.h
	28	of the kernel. But these symbols do not follow the SYS_* syntax
	29	so we have to redefine the `SYS_ify' macro here. */
	30	#undef SYS_ify
6ed0492f	31	#define SYS_ify(syscall_name) __NR_##syscall_name
d2f5be2a	32
8fb3e007 UD	33	/* ELF-like local names start with `.L'. */
	34	#undef L
	35	#define L(name) .L##name
d2f5be2a UD	36
	37	#ifdef ASSEMBLER
	38
cccda09f UD	39	/* Linux uses a negative return value to indicate syscall errors,
	40	unlike most Unices, which use the condition codes' carry flag.
	41
	42	Since version 2.1 the return value of a system call might be
	43	negative even if the call succeeded. E.g., the `lseek' system call
	44	might return a large offset. Therefore we must not anymore test
	45	for < 0, but test for a real error by making sure the value in %eax
b5791037 UD	46	is a real error number. Linus said he will make sure the no syscall
	47	returns a value in -1 .. -4095 as a valid result so we can savely
	48	test with -4095. */
d2f5be2a UD	49	#undef PSEUDO
	50	#define PSEUDO(name, syscall_name, args) \
	51	.text; \
d2f5be2a	52	ENTRY (name) \
c14e4c32	53	DO_CALL (args, syscall_name); \
b5791037	54	cmpl $-4095, %eax; \
ae828bc6 UD	55	jae syscall_error; \
ae828bc6 UD	56	L(pseudo_end):
d2f5be2a	57
6ed0492f UD	58	#undef PSEUDO_END
	59	#define PSEUDO_END(name) \
	60	SYSCALL_ERROR_HANDLER \
	61	END (name)
	62
edf5b2d7	63	#ifndef PIC
03a75825 RM	64	#define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.S is used. */
	65	#else
	66	/* Store (- %eax) into errno through the GOT. */
edf5b2d7	67	#ifdef _LIBC_REENTRANT
03a75825	68	#define SYSCALL_ERROR_HANDLER \
714a562f	69	.type syscall_error,@function; \
edf5b2d7 UD	70	syscall_error: \
	71	pushl %ebx; \
	72	call 0f; \
	73	0:popl %ebx; \
	74	xorl %edx, %edx; \
	75	addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx; \
	76	subl %eax, %edx; \
edf5b2d7 UD	77	pushl %edx; \
	78	call __errno_location@PLT; \
	79	popl %ecx; \
	80	popl %ebx; \
	81	movl %ecx, (%eax); \
	82	movl $-1, %eax; \
ae828bc6	83	jmp L(pseudo_end); \
714a562f	84	.size syscall_error,.-syscall_error;
c4029823	85	/* A quick note: it is assumed that the call to `__errno_location' does
cccda09f	86	not modify the stack! */
edf5b2d7 UD	87	#else
edf5b2d7 UD	88	#define SYSCALL_ERROR_HANDLER \
714a562f	89	.type syscall_error,@function; \
03a75825 RM	90	syscall_error: \
	91	call 0f; \
	92	0:popl %ecx; \
edf5b2d7	93	xorl %edx, %edx; \
03a75825	94	addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ecx; \
edf5b2d7	95	subl %eax, %edx; \
03a75825	96	movl errno@GOT(%ecx), %ecx; \
edf5b2d7	97	movl %edx, (%ecx); \
03a75825	98	movl $-1, %eax; \
ae828bc6	99	jmp L(pseudo_end); \
714a562f	100	.size syscall_error,.-syscall_error;
edf5b2d7 UD	101	#endif /* _LIBC_REENTRANT */
edf5b2d7 UD	102	#endif /* PIC */
03a75825	103
d2f5be2a UD	104	/* Linux takes system call arguments in registers:
	105
	106	syscall number %eax call-clobbered
	107	arg 1 %ebx call-saved
	108	arg 2 %ecx call-clobbered
	109	arg 3 %edx call-clobbered
	110	arg 4 %esi call-saved
	111	arg 5 %edi call-saved
	112
	113	The stack layout upon entering the function is:
	114
	115	20(%esp) Arg# 5
	116	16(%esp) Arg# 4
	117	12(%esp) Arg# 3
	118	8(%esp) Arg# 2
	119	4(%esp) Arg# 1
	120	(%esp) Return address
	121
	122	(Of course a function with say 3 arguments does not have entries for
	123	arguments 4 and 5.)
	124
6ed0492f	125	The following code tries hard to be optimal. A general assumption
03a75825	126	(which is true according to the data books I have) is that
d2f5be2a UD	127
	128	2 * xchg is more expensive than pushl + movl + popl
	129
	130	Beside this a neat trick is used. The calling conventions for Linux
	131	tell that among the registers used for parameters %ecx and %edx need
	132	not be saved. Beside this we may clobber this registers even when
	133	they are not used for parameter passing.
	134
	135	As a result one can see below that we save the content of the %ebx
	136	register in the %edx register when we have less than 3 arguments
	137	(2 * movl is less expensive than pushl + popl).
	138
	139	Second unlike for the other registers we don't save the content of
6ed0492f	140	%ecx and %edx when we have more than 1 and 2 registers resp.
8f5ca04b RM	141
	142	The code below might look a bit long but we have to take care for
	143	the pipelined processors (i586 and up). Here the `pushl' and `popl'
	144	instructions are marked as NP (not pairable) but the exception is
	145	two consecutive of these instruction. This gives no penalty on
	146	i386 and i486 processors though. */
d2f5be2a UD	147
d2f5be2a UD	148	#undef DO_CALL
c14e4c32	149	#define DO_CALL(args, syscall_name) \
8f5ca04b	150	PUSHARGS_##args \
d2f5be2a	151	DOARGS_##args \
c14e4c32	152	movl $SYS_ify (syscall_name), %eax; \
8f5ca04b RM	153	int $0x80 \
8f5ca04b RM	154	POPARGS_##args
d2f5be2a	155
8f5ca04b	156	#define PUSHARGS_0 /* No arguments to push. */
d2f5be2a	157	#define DOARGS_0 /* No arguments to frob. */
8f5ca04b RM	158	#define POPARGS_0 /* No arguments to pop. */
	159	#define _PUSHARGS_0 /* No arguments to push. */
	160	#define _DOARGS_0(n) /* No arguments to frob. */
	161	#define _POPARGS_0 /* No arguments to pop. */
	162
	163	#define PUSHARGS_1 movl %ebx, %edx; PUSHARGS_0
	164	#define DOARGS_1 _DOARGS_1 (4)
	165	#define POPARGS_1 POPARGS_0; movl %edx, %ebx
	166	#define _PUSHARGS_1 pushl %ebx; _PUSHARGS_0
	167	#define _DOARGS_1(n) movl n(%esp), %ebx; _DOARGS_0(n-4)
	168	#define _POPARGS_1 _POPARGS_0; popl %ebx
	169
	170	#define PUSHARGS_2 PUSHARGS_1
	171	#define DOARGS_2 _DOARGS_2 (8)
	172	#define POPARGS_2 POPARGS_1
	173	#define _PUSHARGS_2 _PUSHARGS_1
d2f5be2a	174	#define _DOARGS_2(n) movl n(%esp), %ecx; _DOARGS_1 (n-4)
8f5ca04b	175	#define _POPARGS_2 _POPARGS_1
d2f5be2a	176
8f5ca04b RM	177	#define PUSHARGS_3 _PUSHARGS_2
	178	#define DOARGS_3 _DOARGS_3 (16)
	179	#define POPARGS_3 _POPARGS_3
	180	#define _PUSHARGS_3 _PUSHARGS_2
d2f5be2a	181	#define _DOARGS_3(n) movl n(%esp), %edx; _DOARGS_2 (n-4)
8f5ca04b RM	182	#define _POPARGS_3 _POPARGS_2
	183
	184	#define PUSHARGS_4 _PUSHARGS_4
	185	#define DOARGS_4 _DOARGS_4 (24)
	186	#define POPARGS_4 _POPARGS_4
	187	#define _PUSHARGS_4 pushl %esi; _PUSHARGS_3
	188	#define _DOARGS_4(n) movl n(%esp), %esi; _DOARGS_3 (n-4)
	189	#define _POPARGS_4 _POPARGS_3; popl %esi
	190
	191	#define PUSHARGS_5 _PUSHARGS_5
	192	#define DOARGS_5 _DOARGS_5 (32)
	193	#define POPARGS_5 _POPARGS_5
	194	#define _PUSHARGS_5 pushl %edi; _PUSHARGS_4
	195	#define _DOARGS_5(n) movl n(%esp), %edi; _DOARGS_4 (n-4)
	196	#define _POPARGS_5 _POPARGS_4; popl %edi
d2f5be2a UD	197
d2f5be2a UD	198	#endif /* ASSEMBLER */
ec4b0518 UD	199
ec4b0518 UD	200	#endif /* linux/i386/sysdep.h */