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/* Copyright (C) 1992,1993,1995-2000,2002-2006,2007
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, see
<http://www.gnu.org/licenses/>. */
#ifndef _LINUX_I386_SYSDEP_H
#define _LINUX_I386_SYSDEP_H 1
#include <sys/syscall.h>
#include <common/sysdep.h>
#ifdef __ASSEMBLER__
/* Syntactic details of assembler. */
/* ELF uses byte-counts for .align, most others use log2 of count of bytes. */
#define ALIGNARG(log2) 1<<log2
/* For ELF we need the `.type' directive to make shared libs work right. */
#define ASM_TYPE_DIRECTIVE(name,typearg) .type name,typearg;
#define ASM_SIZE_DIRECTIVE(name) .size name,.-name;
/* In ELF C symbols are asm symbols. */
#undef NO_UNDERSCORES
#define NO_UNDERSCORES
/* Define an entry point visible from C.
There is currently a bug in gdb which prevents us from specifying
incomplete stabs information. Fake some entries here which specify
the current source file. */
#define ENTRY(name) \
.globl C_SYMBOL_NAME(name); \
ASM_TYPE_DIRECTIVE (C_SYMBOL_NAME(name),@function) \
.align ALIGNARG(4); \
C_LABEL(name) \
cfi_startproc;
#undef END
#define END(name) \
cfi_endproc; \
ASM_SIZE_DIRECTIVE(name) \
#ifdef NO_UNDERSCORES
/* Since C identifiers are not normally prefixed with an underscore
on this system, the asm identifier `syscall_error' intrudes on the
C name space. Make sure we use an innocuous name. */
#define syscall_error __syscall_error
#define mcount _mcount
#endif
#undef JUMPTARGET
#ifdef __PIC__
#define JUMPTARGET(name) name##@PLT
#define SYSCALL_PIC_SETUP \
pushl %ebx; \
cfi_adjust_cfa_offset (4); \
call 0f; \
0: popl %ebx; \
cfi_adjust_cfa_offset (-4); \
addl $_GLOBAL_OFFSET_TABLE+[.-0b], %ebx;
# define SETUP_PIC_REG(reg) \
.ifndef __x86.get_pc_thunk.reg; \
.section .gnu.linkonce.t.__x86.get_pc_thunk.reg,"ax",@progbits; \
.globl __x86.get_pc_thunk.reg; \
.hidden __x86.get_pc_thunk.reg; \
.type __x86.get_pc_thunk.reg,@function; \
__x86.get_pc_thunk.reg: \
movl (%esp), %e##reg; \
ret; \
.size __x86.get_pc_thunk.reg, . - __x86.get_pc_thunk.reg; \
.previous; \
.endif; \
call __x86.get_pc_thunk.reg
# define LOAD_PIC_REG(reg) \
SETUP_PIC_REG(reg); addl $_GLOBAL_OFFSET_TABLE_, %e##reg
#else
#define JUMPTARGET(name) name
#define SYSCALL_PIC_SETUP /* Nothing. */
#endif
/* Local label name for asm code. */
#ifndef L
#ifdef HAVE_ELF
#define L(name) .L##name
#else
#define L(name) name
#endif
#endif
/* Avoid conflics with thunk section */
#undef __i686
#endif /* __ASSEMBLER__ */
/* 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
#if defined USE_DL_SYSINFO \
&& (!defined NOT_IN_libc || defined IS_IN_libpthread)
# define I386_USE_SYSENTER 1
#else
# undef I386_USE_SYSENTER
#endif
#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 (syscall_name, args); \
cmpl $-4095, %eax; \
jae SYSCALL_ERROR_LABEL; \
L(pseudo_end):
#undef PSEUDO_END
#define PSEUDO_END(name) \
SYSCALL_ERROR_HANDLER \
END (name)
#undef PSEUDO_NOERRNO
#define PSEUDO_NOERRNO(name, syscall_name, args) \
.text; \
ENTRY (name) \
DO_CALL (syscall_name, args)
#undef PSEUDO_END_NOERRNO
#define PSEUDO_END_NOERRNO(name) \
END (name)
#define ret_NOERRNO ret
/* The function has to return the error code. */
#undef PSEUDO_ERRVAL
#define PSEUDO_ERRVAL(name, syscall_name, args) \
.text; \
ENTRY (name) \
DO_CALL (syscall_name, args); \
negl %eax
#undef PSEUDO_END_ERRVAL
#define PSEUDO_END_ERRVAL(name) \
END (name)
#ifndef __PIC__
# define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.S is used. */
#else
# if defined _LIBC_REENTRANT
# if defined USE___THREAD
# define SYSCALL_ERROR_ERRNO errno
# define SYSCALL_ERROR_HANDLER \
0:SETUP_PIC_REG (cx); \
addl $_GLOBAL_OFFSET_TABLE_, %ecx; \
movl SYSCALL_ERROR_ERRNO@GOTNTPOFF(%ecx), %ecx; \
xorl %edx, %edx; \
subl %eax, %edx; \
SYSCALL_ERROR_HANDLER_TLS_STORE (%edx, %ecx); \
orl $-1, %eax; \
jmp L(pseudo_end);
# ifndef NO_TLS_DIRECT_SEG_REFS
# define SYSCALL_ERROR_HANDLER_TLS_STORE(src, destoff) \
movl src, %gs:(destoff)
# else
# define SYSCALL_ERROR_HANDLER_TLS_STORE(src, destoff) \
addl %gs:0, destoff; \
movl src, (destoff)
# endif
# else
# define SYSCALL_ERROR_HANDLER \
0:pushl %ebx; \
cfi_adjust_cfa_offset (4); \
cfi_rel_offset (ebx, 0); \
SETUP_PIC_REG (bx); \
addl $_GLOBAL_OFFSET_TABLE_, %ebx; \
xorl %edx, %edx; \
subl %eax, %edx; \
pushl %edx; \
cfi_adjust_cfa_offset (4); \
call __errno_location@PLT; \
popl %ecx; \
cfi_adjust_cfa_offset (-4); \
popl %ebx; \
cfi_adjust_cfa_offset (-4); \
cfi_restore (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
/* Store (- %eax) into errno through the GOT. */
# define SYSCALL_ERROR_HANDLER \
0: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__ */
/* The original calling convention for system calls on Linux/i386 is
to use int $0x80. */
#ifdef I386_USE_SYSENTER
# ifdef SHARED
# define ENTER_KERNEL call *%gs:SYSINFO_OFFSET
# else
# define ENTER_KERNEL call *_dl_sysinfo
# endif
#else
# define ENTER_KERNEL int $0x80
#endif
/* 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
arg 6 %ebp call-saved
The stack layout upon entering the function is:
24(%esp) Arg# 6
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, 5, and 6.)
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(syscall_name, args) \
PUSHARGS_##args \
DOARGS_##args \
movl $SYS_ify (syscall_name), %eax; \
ENTER_KERNEL \
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; L(SAVEBX1): PUSHARGS_0
#define DOARGS_1 _DOARGS_1 (4)
#define POPARGS_1 POPARGS_0; movl %edx, %ebx; L(RESTBX1):
#define _PUSHARGS_1 pushl %ebx; cfi_adjust_cfa_offset (4); \
cfi_rel_offset (ebx, 0); L(PUSHBX1): _PUSHARGS_0
#define _DOARGS_1(n) movl n(%esp), %ebx; _DOARGS_0(n-4)
#define _POPARGS_1 _POPARGS_0; popl %ebx; cfi_adjust_cfa_offset (-4); \
cfi_restore (ebx); L(POPBX1):
#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; cfi_adjust_cfa_offset (4); \
cfi_rel_offset (esi, 0); L(PUSHSI1): _PUSHARGS_3
#define _DOARGS_4(n) movl n(%esp), %esi; _DOARGS_3 (n-4)
#define _POPARGS_4 _POPARGS_3; popl %esi; cfi_adjust_cfa_offset (-4); \
cfi_restore (esi); L(POPSI1):
#define PUSHARGS_5 _PUSHARGS_5
#define DOARGS_5 _DOARGS_5 (32)
#define POPARGS_5 _POPARGS_5
#define _PUSHARGS_5 pushl %edi; cfi_adjust_cfa_offset (4); \
cfi_rel_offset (edi, 0); L(PUSHDI1): _PUSHARGS_4
#define _DOARGS_5(n) movl n(%esp), %edi; _DOARGS_4 (n-4)
#define _POPARGS_5 _POPARGS_4; popl %edi; cfi_adjust_cfa_offset (-4); \
cfi_restore (edi); L(POPDI1):
#define PUSHARGS_6 _PUSHARGS_6
#define DOARGS_6 _DOARGS_6 (40)
#define POPARGS_6 _POPARGS_6
#define _PUSHARGS_6 pushl %ebp; cfi_adjust_cfa_offset (4); \
cfi_rel_offset (ebp, 0); L(PUSHBP1): _PUSHARGS_5
#define _DOARGS_6(n) movl n(%esp), %ebp; _DOARGS_5 (n-4)
#define _POPARGS_6 _POPARGS_5; popl %ebp; cfi_adjust_cfa_offset (-4); \
cfi_restore (ebp); L(POPBP1):
#endif /* __ASSEMBLER__ */
#endif /* linux/i386/sysdep.h */
|
