summaryrefslogtreecommitdiff
path: root/libc/sysdeps/linux/i386/syscall.S
diff options
context:
space:
mode:
authorEric Andersen <andersen@codepoet.org>2002-07-24 19:51:46 +0000
committerEric Andersen <andersen@codepoet.org>2002-07-24 19:51:46 +0000
commit255cd531d67d4c5d110409e2a24e2aa5a6249a7a (patch)
tree9d1ef2999a4e4fc28644e01376684862e03b82dc /libc/sysdeps/linux/i386/syscall.S
parentbb364bda4be59f9141c1727524ffe459a742ddee (diff)
Add support for people calling syscall()
-Erik
Diffstat (limited to 'libc/sysdeps/linux/i386/syscall.S')
-rw-r--r--libc/sysdeps/linux/i386/syscall.S76
1 files changed, 76 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/i386/syscall.S b/libc/sysdeps/linux/i386/syscall.S
new file mode 100644
index 000000000..c67b39ece
--- /dev/null
+++ b/libc/sysdeps/linux/i386/syscall.S
@@ -0,0 +1,76 @@
+/*
+ * June 27, 2001 Manuel Novoa III
+ *
+ * This is a heavily modified version of gcc's output for the _syscall5 macro.
+ * The idea (originally from dietlibc) is that all syscall functions simply set
+ * the syscall number as the first argument, then set the syscall arguments as
+ * the next up-to-five arguments, and then jump here. All the common work is
+ * done by syscall(), saving a fair amount of generated code when a number of
+ * syscalls are used. The (potential) cost is some unnecessary pushes, pops,
+ * and movs but the execution time penalty should be relatively small compared
+ * to the cost of the syscall itself.
+ *
+ * July 24, 2002
+ *
+ * Modified by Erik Andersen to take all function parameters from off the stack
+ * like a proper function and eliminates the old 255 syscall number limit. So
+ * now we can just call this as a function as syscall() per the function
+ * prototype in unistd.h, so to call _exit(42) you can just call.
+ * syscall(__NR_exit, 42);
+ * and things will just work.
+ */
+
+.text
+ .align 4
+.globl syscall
+ .type syscall,@function
+syscall:
+ pushl %edi
+ pushl %esi
+ pushl %ebx
+ movl 36(%esp),%edi; /* Load the 5 syscall argument registers */
+ movl 32(%esp),%esi;
+ movl 28(%esp),%edx;
+ movl 24(%esp),%ecx;
+ movl 20(%esp),%ebx;
+ movl 16(%esp),%eax /* Load syscall number into %eax. */
+#APP
+ int $0x80
+#NO_APP
+ cmpl $-4095,%eax
+ jbe .Ldone
+
+#ifdef PIC
+ call Lhere
+Lhere:
+ popl %ebx
+ addl $_GLOBAL_OFFSET_TABLE_+[.-Lhere],%ebx
+ negl %eax
+ movl %eax,%ecx
+#ifdef _LIBC_REENTRANT
+ call __errno_location@PLT
+#else
+ movl errno@GOT(%ebx),%eax
+#endif /* _LIBC_REENTRANT */
+ movl %ecx,(%eax)
+#else
+ negl %eax
+#ifdef _LIBC_REENTRANT
+ movl %eax,%ecx
+ call __errno_location
+ movl %ecx,(%eax)
+#else
+ movl %eax,errno
+#endif /* _LIBC_REENTRANT */
+
+#endif /* PIC */
+
+ movl $-1,%eax
+ .p2align 4,,7
+.Ldone:
+ popl %ebx
+ popl %esi
+ popl %edi
+ ret
+.Lsize:
+ .size syscall,.Lsize-syscall