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authorDenys Vlasenko <vda.linux@googlemail.com>2010-04-06 05:28:29 +0200
committerDenys Vlasenko <vda.linux@googlemail.com>2010-04-06 05:28:29 +0200
commiteefaf06888e3dcbc410b4cc2d231035f4400c7ac (patch)
treea4c140b8faf2a2891b40498567126c5cf9af910a /libc/sysdeps/linux/i386/bits
parentb2f0faf04264c13d7877646330da7f5954380342 (diff)
i386/bits/syscalls.h: explain how it works. no code changes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'libc/sysdeps/linux/i386/bits')
-rw-r--r--libc/sysdeps/linux/i386/bits/syscalls.h216
1 files changed, 116 insertions, 100 deletions
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 <bits/syscalls.h> directly; include <sys/syscall.h> 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 <errno.h>
-/* 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) \