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

/* Copyright (C) 1992, 1993, 1995 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.  */

/* In the Linux/ELF world, C symbols are asm symbols.  */
#define NO_UNDERSCORES

/* 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;								      \
  .globl syscall_error;							      \
  ENTRY (name)								      \
    movl $SYS_ify (syscall_name), %eax;					      \
    DO_CALL (args);							      \
    testl %eax, %eax;							      \
    jl JUMPTARGET (syscall_error)

/* We define our own ENTRY macro because the alignment should be 16 for ELF.  */
#undef ENTRY
#define ENTRY(name)							      \
  ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (name);				      \
  ASM_TYPE_DIRECTIVE (C_SYMBOL_NAME (name), @function)			      \
  .align 16;								      \
  C_LABEL (name)

/* 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 accoriding 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.  */

#undef	DO_CALL
#define DO_CALL(args)					      		      \
    DOARGS_##args							      \
    int $0x80;								      \
    UNDOARGS_##args

#define	DOARGS_0	/* No arguments to frob.  */
#define	UNDOARGS_0	/* No arguments to unfrob.  */
#define	_DOARGS_0(n)	/* No arguments to frob.  */
#define	_UNDOARGS_0	/* No arguments to unfrob.  */

#define	DOARGS_1	movl %ebx, %edx; movl 4(%esp), %ebx; DOARGS_0
#define	UNDOARGS_1	UNDOARGS_0; movl %edx, %ebx
#define	_DOARGS_1(n)	pushl %ebx; movl n+4(%esp), %ebx; _DOARGS_0 (n)
#define	_UNDOARGS_1	_UNDOARGS_0; popl %ebx

#define	DOARGS_2	movl 8(%esp), %ecx; DOARGS_1
#define	UNDOARGS_2	UNDOARGS_1
#define	_DOARGS_2(n)	movl n(%esp), %ecx; _DOARGS_1 (n-4)
#define	_UNDOARGS_2	_UNDOARGS_1

#define DOARGS_3	_DOARGS_3 (12)
#define UNDOARGS_3	_UNDOARGS_3
#define _DOARGS_3(n)	movl n(%esp), %edx; _DOARGS_2 (n-4)
#define _UNDOARGS_3	_UNDOARGS_2

#define DOARGS_4	_DOARGS_4 (16)
#define UNDOARGS_4	_UNDOARGS_4
#define _DOARGS_4(n)	pushl %esi; movl n+4(%esp), %esi; _DOARGS_3 (n)
#define _UNDOARGS_4	_UNDOARGS_3; popl %esi

#define DOARGS_5	_DOARGS_5 (20)
#define UNDOARGS_5	_UNDOARGS_5
#define _DOARGS_5(n)	pushl %edi; movl n+4(%esp), %edi; _DOARGS_4 (n)
#define _UNDOARGS_5	_UNDOARGS_4; popl %edi


#endif	/* ASSEMBLER */
Commit	Line	Data
d2f5be2a UD	1	/* Copyright (C) 1992, 1993, 1995 Free Software Foundation, Inc.
	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
	20	/* In the Linux/ELF world, C symbols are asm symbols. */
	21	#define NO_UNDERSCORES
	22
	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
	31	#ifdef __STDC__
	32	# define SYS_ify(syscall_name) __NR_##syscall_name
	33	#else
	34	# define SYS_ify(syscall_name) __NR_/**/syscall_name
	35	#endif
	36
	37
	38	#ifdef ASSEMBLER
	39
	40	/* Linux uses a negative return value to indicate syscall errors, unlike
	41	most Unices, which use the condition codes' carry flag. */
	42	#undef PSEUDO
	43	#define PSEUDO(name, syscall_name, args) \
	44	.text; \
	45	.globl syscall_error; \
	46	ENTRY (name) \
	47	movl $SYS_ify (syscall_name), %eax; \
	48	DO_CALL (args); \
	49	testl %eax, %eax; \
	50	jl JUMPTARGET (syscall_error)
	51
	52	/* We define our own ENTRY macro because the alignment should be 16 for ELF. */
	53	#undef ENTRY
	54	#define ENTRY(name) \
	55	ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME (name); \
	56	ASM_TYPE_DIRECTIVE (C_SYMBOL_NAME (name), @function) \
	57	.align 16; \
	58	C_LABEL (name)
	59
	60	/* Linux takes system call arguments in registers:
	61
	62	syscall number %eax call-clobbered
	63	arg 1 %ebx call-saved
	64	arg 2 %ecx call-clobbered
65	arg 3 %edx call-clobbered
66	arg 4 %esi call-saved
67	arg 5 %edi call-saved
68
69	The stack layout upon entering the function is:
70
71	20(%esp) Arg# 5
72	16(%esp) Arg# 4
73	12(%esp) Arg# 3
74	8(%esp) Arg# 2
75	4(%esp) Arg# 1
76	(%esp) Return address
77
78	(Of course a function with say 3 arguments does not have entries for
79	arguments 4 and 5.)
80
81	The following code tries hard to be optimal. A general assuption
82	(which is true accoriding to the data books I have) is that
83
84	2 * xchg is more expensive than pushl + movl + popl
85
86	Beside this a neat trick is used. The calling conventions for Linux
87	tell that among the registers used for parameters %ecx and %edx need
88	not be saved. Beside this we may clobber this registers even when
89	they are not used for parameter passing.
90
91	As a result one can see below that we save the content of the %ebx
92	register in the %edx register when we have less than 3 arguments
93	(2 * movl is less expensive than pushl + popl).
94
95	Second unlike for the other registers we don't save the content of
96	%ecx and %edx when we have than 1 and 2 registers resp. */
97
98	#undef DO_CALL
99	#define DO_CALL(args) \
100	DOARGS_##args \
101	int $0x80; \
102	UNDOARGS_##args
103
104	#define DOARGS_0 /* No arguments to frob. */
105	#define UNDOARGS_0 /* No arguments to unfrob. */
106	#define _DOARGS_0(n) /* No arguments to frob. */
107	#define _UNDOARGS_0 /* No arguments to unfrob. */
108
109	#define DOARGS_1 movl %ebx, %edx; movl 4(%esp), %ebx; DOARGS_0
110	#define UNDOARGS_1 UNDOARGS_0; movl %edx, %ebx
111	#define _DOARGS_1(n) pushl %ebx; movl n+4(%esp), %ebx; _DOARGS_0 (n)
112	#define _UNDOARGS_1 _UNDOARGS_0; popl %ebx
113
114	#define DOARGS_2 movl 8(%esp), %ecx; DOARGS_1
115	#define UNDOARGS_2 UNDOARGS_1
116	#define _DOARGS_2(n) movl n(%esp), %ecx; _DOARGS_1 (n-4)
117	#define _UNDOARGS_2 _UNDOARGS_1
118
119	#define DOARGS_3 _DOARGS_3 (12)
120	#define UNDOARGS_3 _UNDOARGS_3
121	#define _DOARGS_3(n) movl n(%esp), %edx; _DOARGS_2 (n-4)
122	#define _UNDOARGS_3 _UNDOARGS_2
123
124	#define DOARGS_4 _DOARGS_4 (16)
125	#define UNDOARGS_4 _UNDOARGS_4
126	#define _DOARGS_4(n) pushl %esi; movl n+4(%esp), %esi; _DOARGS_3 (n)
127	#define _UNDOARGS_4 _UNDOARGS_3; popl %esi
128
129	#define DOARGS_5 _DOARGS_5 (20)
130	#define UNDOARGS_5 _UNDOARGS_5
131	#define _DOARGS_5(n) pushl %edi; movl n+4(%esp), %edi; _DOARGS_4 (n)
132	#define _UNDOARGS_5 _UNDOARGS_4; popl %edi
133
134
135	#endif /* ASSEMBLER */