[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.  */

/* 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 (args, syscall_name);					      \
    cmpl $-4095, %eax;							      \
    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.  */
#else
/* Store (- %eax) into errno through the GOT.  */
#ifdef _LIBC_REENTRANT
#define SYSCALL_ERROR_HANDLER						      \
0:pushl %ebx;								      \
  call 1f;								      \
1:popl %ebx;								      \
  xorl %edx, %edx;							      \
  addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx;				      \
  subl %eax, %edx;							      \
  pushl %edx;								      \
  call __errno_location@PLT;						      \
  popl %ecx;								      \
  popl %ebx;								      \
  movl %ecx, (%eax);							      \
  movl $-1, %eax;							      \
  jmp L(pseudo_end);
/* A quick note: it is assumed that the call to `__errno_location' does
   not modify the stack!  */
#else
#define SYSCALL_ERROR_HANDLER						      \
0:call 1f;								      \
1:popl %ecx;								      \
  xorl %edx, %edx;							      \
  addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx;				      \
  subl %eax, %edx;							      \
  movl errno@GOT(%ecx), %ecx;						      \
  movl %edx, (%ecx);							      \
  movl $-1, %eax;							      \
  jmp L(pseudo_end);
#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).  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
   other 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	36
66715f83	37	#ifdef __ASSEMBLER__
d2f5be2a	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. */
c0fb8a56 UD	49
	50	/* We don't want the label for the error handle to be global when we define
	51	it here. */
	52	#ifdef PIC
	53	# define SYSCALL_ERROR_LABEL 0f
	54	#else
	55	# define SYSCALL_ERROR_LABEL syscall_error
	56	#endif
	57
d2f5be2a UD	58	#undef PSEUDO
	59	#define PSEUDO(name, syscall_name, args) \
	60	.text; \
d2f5be2a	61	ENTRY (name) \
c14e4c32	62	DO_CALL (args, syscall_name); \
b5791037	63	cmpl $-4095, %eax; \
c0fb8a56	64	jae SYSCALL_ERROR_LABEL; \
ae828bc6	65	L(pseudo_end):
d2f5be2a	66
6ed0492f UD	67	#undef PSEUDO_END
	68	#define PSEUDO_END(name) \
	69	SYSCALL_ERROR_HANDLER \
	70	END (name)
	71
edf5b2d7	72	#ifndef PIC
03a75825 RM	73	#define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.S is used. */
	74	#else
	75	/* Store (- %eax) into errno through the GOT. */
edf5b2d7	76	#ifdef _LIBC_REENTRANT
03a75825	77	#define SYSCALL_ERROR_HANDLER \
c0fb8a56 UD	78	0:pushl %ebx; \
	79	call 1f; \
	80	1:popl %ebx; \
edf5b2d7	81	xorl %edx, %edx; \
c0fb8a56	82	addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx; \
edf5b2d7	83	subl %eax, %edx; \
edf5b2d7 UD	84	pushl %edx; \
	85	call __errno_location@PLT; \
	86	popl %ecx; \
	87	popl %ebx; \
	88	movl %ecx, (%eax); \
	89	movl $-1, %eax; \
c0fb8a56	90	jmp L(pseudo_end);
c4029823	91	/* A quick note: it is assumed that the call to `__errno_location' does
cccda09f	92	not modify the stack! */
edf5b2d7 UD	93	#else
edf5b2d7 UD	94	#define SYSCALL_ERROR_HANDLER \
c0fb8a56 UD	95	0:call 1f; \
c0fb8a56 UD	96	1:popl %ecx; \
edf5b2d7	97	xorl %edx, %edx; \
c0fb8a56	98	addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx; \
edf5b2d7	99	subl %eax, %edx; \
03a75825	100	movl errno@GOT(%ecx), %ecx; \
edf5b2d7	101	movl %edx, (%ecx); \
03a75825	102	movl $-1, %eax; \
c0fb8a56	103	jmp L(pseudo_end);
edf5b2d7 UD	104	#endif /* _LIBC_REENTRANT */
edf5b2d7 UD	105	#endif /* PIC */
03a75825	106
d2f5be2a UD	107	/* Linux takes system call arguments in registers:
	108
	109	syscall number %eax call-clobbered
	110	arg 1 %ebx call-saved
	111	arg 2 %ecx call-clobbered
	112	arg 3 %edx call-clobbered
	113	arg 4 %esi call-saved
	114	arg 5 %edi call-saved
	115
	116	The stack layout upon entering the function is:
	117
	118	20(%esp) Arg# 5
	119	16(%esp) Arg# 4
	120	12(%esp) Arg# 3
	121	8(%esp) Arg# 2
	122	4(%esp) Arg# 1
	123	(%esp) Return address
	124
	125	(Of course a function with say 3 arguments does not have entries for
	126	arguments 4 and 5.)
	127
6ed0492f	128	The following code tries hard to be optimal. A general assumption
03a75825	129	(which is true according to the data books I have) is that
d2f5be2a UD	130
	131	2 * xchg is more expensive than pushl + movl + popl
	132
	133	Beside this a neat trick is used. The calling conventions for Linux
	134	tell that among the registers used for parameters %ecx and %edx need
	135	not be saved. Beside this we may clobber this registers even when
	136	they are not used for parameter passing.
	137
	138	As a result one can see below that we save the content of the %ebx
	139	register in the %edx register when we have less than 3 arguments
	140	(2 * movl is less expensive than pushl + popl).
	141
	142	Second unlike for the other registers we don't save the content of
6ed0492f	143	%ecx and %edx when we have more than 1 and 2 registers resp.
8f5ca04b RM	144
8f5ca04b RM	145	The code below might look a bit long but we have to take care for
63bda0c1	146	the pipelined processors (i586). Here the `pushl' and `popl'
8f5ca04b RM	147	instructions are marked as NP (not pairable) but the exception is
8f5ca04b RM	148	two consecutive of these instruction. This gives no penalty on
63bda0c1	149	other processors though. */
d2f5be2a UD	150
d2f5be2a UD	151	#undef DO_CALL
c14e4c32	152	#define DO_CALL(args, syscall_name) \
8f5ca04b	153	PUSHARGS_##args \
d2f5be2a	154	DOARGS_##args \
c14e4c32	155	movl $SYS_ify (syscall_name), %eax; \
8f5ca04b RM	156	int $0x80 \
8f5ca04b RM	157	POPARGS_##args
d2f5be2a	158
8f5ca04b	159	#define PUSHARGS_0 /* No arguments to push. */
d2f5be2a	160	#define DOARGS_0 /* No arguments to frob. */
8f5ca04b RM	161	#define POPARGS_0 /* No arguments to pop. */
	162	#define _PUSHARGS_0 /* No arguments to push. */
	163	#define _DOARGS_0(n) /* No arguments to frob. */
	164	#define _POPARGS_0 /* No arguments to pop. */
	165
	166	#define PUSHARGS_1 movl %ebx, %edx; PUSHARGS_0
	167	#define DOARGS_1 _DOARGS_1 (4)
	168	#define POPARGS_1 POPARGS_0; movl %edx, %ebx
	169	#define _PUSHARGS_1 pushl %ebx; _PUSHARGS_0
	170	#define _DOARGS_1(n) movl n(%esp), %ebx; _DOARGS_0(n-4)
	171	#define _POPARGS_1 _POPARGS_0; popl %ebx
	172
	173	#define PUSHARGS_2 PUSHARGS_1
	174	#define DOARGS_2 _DOARGS_2 (8)
	175	#define POPARGS_2 POPARGS_1
	176	#define _PUSHARGS_2 _PUSHARGS_1
d2f5be2a	177	#define _DOARGS_2(n) movl n(%esp), %ecx; _DOARGS_1 (n-4)
8f5ca04b	178	#define _POPARGS_2 _POPARGS_1
d2f5be2a	179
8f5ca04b RM	180	#define PUSHARGS_3 _PUSHARGS_2
	181	#define DOARGS_3 _DOARGS_3 (16)
	182	#define POPARGS_3 _POPARGS_3
	183	#define _PUSHARGS_3 _PUSHARGS_2
d2f5be2a	184	#define _DOARGS_3(n) movl n(%esp), %edx; _DOARGS_2 (n-4)
8f5ca04b RM	185	#define _POPARGS_3 _POPARGS_2
	186
	187	#define PUSHARGS_4 _PUSHARGS_4
	188	#define DOARGS_4 _DOARGS_4 (24)
	189	#define POPARGS_4 _POPARGS_4
	190	#define _PUSHARGS_4 pushl %esi; _PUSHARGS_3
	191	#define _DOARGS_4(n) movl n(%esp), %esi; _DOARGS_3 (n-4)
	192	#define _POPARGS_4 _POPARGS_3; popl %esi
	193
	194	#define PUSHARGS_5 _PUSHARGS_5
	195	#define DOARGS_5 _DOARGS_5 (32)
	196	#define POPARGS_5 _POPARGS_5
	197	#define _PUSHARGS_5 pushl %edi; _PUSHARGS_4
	198	#define _DOARGS_5(n) movl n(%esp), %edi; _DOARGS_4 (n-4)
	199	#define _POPARGS_5 _POPARGS_4; popl %edi
d2f5be2a	200
66715f83	201	#endif /* __ASSEMBLER__ */
ec4b0518 UD	202
ec4b0518 UD	203	#endif /* linux/i386/sysdep.h */