From eefaf06888e3dcbc410b4cc2d231035f4400c7ac Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 6 Apr 2010 05:28:29 +0200 Subject: i386/bits/syscalls.h: explain how it works. no code changes Signed-off-by: Denys Vlasenko --- libc/sysdeps/linux/i386/bits/syscalls.h | 216 +++++++++++++++++--------------- 1 file changed, 116 insertions(+), 100 deletions(-) (limited to 'libc') diff --git a/libc/sysdeps/linux/i386/bits/syscalls.h b/libc/sysdeps/linux/i386/bits/syscalls.h index 23d872a29..46c2d9962 100644 --- a/libc/sysdeps/linux/i386/bits/syscalls.h +++ b/libc/sysdeps/linux/i386/bits/syscalls.h @@ -1,128 +1,144 @@ #ifndef _BITS_SYSCALLS_H #define _BITS_SYSCALLS_H + #ifndef _SYSCALL_H # error "Never use directly; include instead." #endif /* - Some of the sneaky macros in the code were taken from - glibc-2.2.5/sysdeps/unix/sysv/linux/i386/sysdep.h -*/ + * Some of the sneaky macros in the code were taken from + * glibc-2.2.5/sysdeps/unix/sysv/linux/i386/sysdep.h + */ #ifndef __ASSEMBLER__ #include -/* We need some help from the assembler to generate optimal code. We - define some macros here which later will be used. */ +/* We need some help from the assembler to generate optimal code. + * We define some macros here which later will be used. */ -#if defined __SUPPORT_LD_DEBUG__ && defined __DOMULTI__ +#if defined __SUPPORT_LD_DEBUG__ && defined __DOMULTI__ #error LD debugging and DOMULTI are incompatible #endif #ifdef __DOMULTI__ -__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" - ".ifndef _BITS_SYSCALLS_ASM\n\t" - ".set _BITS_SYSCALLS_ASM,1\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" - ".endif\n\t"); +__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" + + ".ifndef _BITS_SYSCALLS_ASM\n\t" + ".set _BITS_SYSCALLS_ASM,1\n\t" + + /* Loading param #1 (ebx) is done by loading it into + * another register, and then performing bpushl+bmovl, + * since we must preserve ebx */ + + ".macro bpushl name reg\n\t" + ".if 1 - \\name\n\t" /* if reg!=ebx... */ + ".if 2 - \\name\n\t" /* if reg can't be clobbered... */ + "pushl %ebx\n\t" /* save ebx on stack */ + ".else\n\t" + "xchgl \\reg, %ebx\n\t" /* else save ebx in reg, and load reg to ebx */ + ".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" /* if reg can't be clobbered... */ + "movl \\reg, %ebx\n\t" /* load reg to ebx */ + ".endif\n\t" + ".endif\n\t" + ".endm\n\t" + + ".endif\n\t" /* _BITS_SYSCALLS_ASM */ + + ".macro bpopl name reg\n\t" + ".if 1 - \\name\n\t" + ".if 2 - \\name\n\t" /* if reg can't be clobbered... */ + "popl %ebx\n\t" /* restore ebx from stack */ + ".else\n\t" + "xchgl \\reg, %ebx\n\t" /* else restore ebx from reg */ + ".endif\n\t" + ".endif\n\t" + ".endm\n\t" +); #else -__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"); +__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 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" + + ".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" +); #endif #define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \ - ({ \ - register unsigned int resultvar; \ - __asm__ __volatile__ ( \ - LOADARGS_##nr \ - "movl %1, %%eax\n\t" \ - "int $0x80\n\t" \ - RESTOREARGS_##nr \ - : "=a" (resultvar) \ - : "i" (name) ASMFMT_##nr(args) : "memory", "cc"); \ - (int) resultvar; }) +({ \ + register unsigned int resultvar; \ + __asm__ __volatile__ ( \ + LOADARGS_##nr \ + "movl %1, %%eax\n\t" \ + "int $0x80\n\t" \ + RESTOREARGS_##nr \ + : "=a" (resultvar) \ + : "i" (name) ASMFMT_##nr(args) : "memory", "cc" \ + ); \ + (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 LOADARGS_6 LOADARGS_1 "push %%ebp ; movl %7, %%ebp\n\t" +#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 LOADARGS_6 LOADARGS_1 "push %%ebp\n\t" "movl %7, %%ebp\n\t" #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 RESTOREARGS_6 "pop %%ebp\n\t" RESTOREARGS_1 +#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 RESTOREARGS_6 "pop %%ebp\n\t" RESTOREARGS_1 #define ASMFMT_0() #define ASMFMT_1(arg1) \ -- cgit v1.2.3