/* 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 */