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Diffstat (limited to 'sysdeps/unix/sysv/linux/i386/sysdep.h')
| -rw-r--r-- | sysdeps/unix/sysv/linux/i386/sysdep.h | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h b/sysdeps/unix/sysv/linux/i386/sysdep.h new file mode 100644 index 0000000000..7fe4d414e3 --- /dev/null +++ b/sysdeps/unix/sysv/linux/i386/sysdep.h @@ -0,0 +1,135 @@ +/* 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 */ |