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/* Copyright (C) 1992, 1993, 1995-2000, 2002 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper, <drepper@gnu.org>, August 1995.
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, 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>
#include <bp-sym.h>
#include <bp-asm.h>
#include <tls.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
#ifdef __ASSEMBLER__
/* ELF-like local names start with `.L'. */
#undef L
#define L(name) .L##name
/* 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
# ifndef HAVE_HIDDEN
# define SETUP_PIC_REG(reg) \
call 1f; \
.subsection 1; \
1:movl (%esp), %e##reg; \
ret; \
.previous
# else
# define SETUP_PIC_REG(reg) \
.section .gnu.linkonce.t.__i686.get_pc_thunk.reg,"ax",@progbits; \
.globl __i686.get_pc_thunk.reg; \
.hidden __i686.get_pc_thunk.reg; \
.type __i686.get_pc_thunk.reg,@function; \
__i686.get_pc_thunk.reg: \
movl (%esp), %e##reg; \
ret; \
.previous; \
call __i686.get_pc_thunk.reg
# endif
/* Store (- %eax) into errno through the GOT. */
# ifdef _LIBC_REENTRANT
# if USE_TLS && HAVE___THREAD
# define SYSCALL_ERROR_HANDLER \
0:SETUP_PIC_REG (cx); \
addl $_GLOBAL_OFFSET_TABLE_, %ecx; \
xorl %edx, %edx; \
subl %eax, %edx; \
movl %gs:0, %eax; \
subl errno@gottpoff(%ecx), %eax; \
movl %edx, (%eax); \
orl $-1, %eax; \
jmp L(pseudo_end);
# else
# define SYSCALL_ERROR_HANDLER \
0:pushl %ebx; \
SETUP_PIC_REG (bx); \
addl $_GLOBAL_OFFSET_TABLE_, %ebx; \
xorl %edx, %edx; \
subl %eax, %edx; \
pushl %edx; \
PUSH_ERRNO_LOCATION_RETURN; \
call BP_SYM (__errno_location)@PLT; \
POP_ERRNO_LOCATION_RETURN; \
popl %ecx; \
popl %ebx; \
movl %ecx, (%eax); \
orl $-1, %eax; \
jmp L(pseudo_end);
/* A quick note: it is assumed that the call to `__errno_location' does
not modify the stack! */
# endif
# else
# define SYSCALL_ERROR_HANDLER \
0:define SETUP_PIC_REG(cx); \
addl $_GLOBAL_OFFSET_TABLE_, %ecx; \
xorl %edx, %edx; \
subl %eax, %edx; \
movl errno@GOT(%ecx), %ecx; \
movl %edx, (%ecx); \
orl $-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
#else /* !__ASSEMBLER__ */
/* We need some help from the assembler to generate optimal code. We
define some macros here which later will be used. */
asm (".L__X'%ebx = 1\n\t"
".L__X'%ecx = 2\n\t"
".L__X'%edx = 2\n\t"
".L__X'%eax = 3\n\t"
".L__X'%esi = 3\n\t"
".L__X'%edi = 3\n\t"
".L__X'%ebp = 3\n\t"
".L__X'%esp = 3\n\t"
".macro bpushl name reg\n\t"
".if 1 - \\name\n\t"
".if 2 - \\name\n\t"
"pushl %ebx\n\t"
".else\n\t"
"xchgl \\reg, %ebx\n\t"
".endif\n\t"
".endif\n\t"
".endm\n\t"
".macro bpopl name reg\n\t"
".if 1 - \\name\n\t"
".if 2 - \\name\n\t"
"popl %ebx\n\t"
".else\n\t"
"xchgl \\reg, %ebx\n\t"
".endif\n\t"
".endif\n\t"
".endm\n\t"
".macro bmovl name reg\n\t"
".if 1 - \\name\n\t"
".if 2 - \\name\n\t"
"movl \\reg, %ebx\n\t"
".endif\n\t"
".endif\n\t"
".endm\n\t");
/* Define a macro which expands inline into the wrapper code for a system
call. */
#undef INLINE_SYSCALL
#define INLINE_SYSCALL(name, nr, args...) \
({ \
unsigned int resultvar; \
asm volatile ( \
LOADARGS_##nr \
"movl %1, %%eax\n\t" \
"int $0x80\n\t" \
RESTOREARGS_##nr \
: "=a" (resultvar) \
: "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc"); \
if (resultvar >= 0xfffff001) \
{ \
__set_errno (-resultvar); \
resultvar = 0xffffffff; \
} \
(int) resultvar; })
#define LOADARGS_0
#define LOADARGS_1 \
"bpushl .L__X'%k2, %k2\n\t" \
"bmovl .L__X'%k2, %k2\n\t"
#define LOADARGS_2 LOADARGS_1
#define LOADARGS_3 LOADARGS_1
#define LOADARGS_4 LOADARGS_1
#define LOADARGS_5 LOADARGS_1
#define RESTOREARGS_0
#define RESTOREARGS_1 \
"bpopl .L__X'%k2, %k2\n\t"
#define RESTOREARGS_2 RESTOREARGS_1
#define RESTOREARGS_3 RESTOREARGS_1
#define RESTOREARGS_4 RESTOREARGS_1
#define RESTOREARGS_5 RESTOREARGS_1
#define ASMFMT_0()
#define ASMFMT_1(arg1) \
, "acdSD" (arg1)
#define ASMFMT_2(arg1, arg2) \
, "adCD" (arg1), "c" (arg2)
#define ASMFMT_3(arg1, arg2, arg3) \
, "aCD" (arg1), "c" (arg2), "d" (arg3)
#define ASMFMT_4(arg1, arg2, arg3, arg4) \
, "aD" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
#define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
, "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)
#endif /* __ASSEMBLER__ */
#endif /* linux/i386/sysdep.h */
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