Optimize for kernels which are known to have the vfork syscall. Don't confuse the...

diff --git a/sysdeps/unix/sysv/linux/i386/vfork.S b/sysdeps/unix/sysv/linux/i386/vfork.S
index 6f7477e89d796c727b07a0abc72d51ef8677aff8..59657e49c02b1a15c3d6349e763cde24a4521e9d 100644 (file)
--- a/sysdeps/unix/sysv/linux/i386/vfork.S
+++ b/sysdeps/unix/sysv/linux/i386/vfork.S
@@ -1,4 +1,4 @@
-/* Copyright (C) 1999 Free Software Foundation, Inc.
+/* Copyright (C) 1999, 2002 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Andreas Schwab <schwab@gnu.org>.
 
@@ -20,6 +20,7 @@
 #include <sysdep.h>
 #define _ERRNO_H       1
 #include <bits/errno.h>
+#include <kernel-features.h>
 
 /* Clone the calling process, but without copying the whole address space.
    The calling process is suspended until the new process exits or is
@@ -36,22 +37,32 @@ ENTRY (__vfork)
        /* Stuff the syscall number in EAX and enter into the kernel.  */
        movl    $SYS_ify (vfork), %eax
        int     $0x80
+
+       /* Jump to the return PC.  Don't jump directly since this
+          disturbs the branch target cache.  Instead push the return
+          address back on the stack.  */
+       pushl   %ecx
+
        cmpl    $-4095, %eax
-       jae     .Lerror         /* Branch forward if it failed.  */
+       /* Branch forward if it failed.  */
+# ifdef __ASSUME_VFORK_SYSCALL
+       jae     SYSCALL_ERROR_LABEL
+.Lpseudo_end:
+# else
+       jae     .Lerror
+# endif
 
-       /* Jump to the return PC.  */
-       jmp     *%ecx
+       ret
 
+# ifndef __ASSUME_VFORK_SYSCALL
 .Lerror:
-       /* Push back the return PC.  */
-       pushl   %ecx
-
        /* Check if vfork syscall is known at all.  */
        cmpl    $-ENOSYS, %eax
        jne     SYSCALL_ERROR_LABEL
-
+# endif
 #endif
 
+#ifndef __ASSUME_VFORK_SYSCALL
        /* If we don't have vfork, fork is close enough.  */
 
        movl    $SYS_ify (fork), %eax
@@ -60,7 +71,7 @@ ENTRY (__vfork)
        jae     SYSCALL_ERROR_LABEL
 .Lpseudo_end:
        ret
-
+#endif
 PSEUDO_END (__vfork)
 
 weak_alias (__vfork, vfork)