generic sys_fork / sys_vfork / sys_clone

... and get rid of idiotic struct pt_regs * in asm-generic/syscalls.h
prototypes of the same, while we are at it.  Eventually we want those
in linux/syscalls.h, of course, but that'll have to wait a bit.

Note that there are *three* variants of sys_clone() order of arguments.
Braindamage galore...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/Kconfig

@@ -341,4 +341,18 @@ config MODULES_USE_ELF_REL
 	  Modules only use ELF REL relocations.  Modules with ELF RELA
 	  relocations will give an error.
 
+#
+# ABI hall of shame
+#
+config CLONE_BACKWARDS
+	bool
+	help
+	  Architecture has tls passed as the 4th argument of clone(2),
+	  not the 5th one.
+
+config CLONE_BACKWARDS2
+	bool
+	help
+	  Architecture has the first two arguments of clone(2) swapped.
+
 source "kernel/gcov/Kconfig"

include/asm-generic/syscalls.h

@@ -10,16 +10,15 @@
  */
 #ifndef sys_clone
 asmlinkage long sys_clone(unsigned long clone_flags, unsigned long newsp,
-			void __user *parent_tid, void __user *child_tid,
+			void __user *parent_tid, void __user *child_tid);
-			struct pt_regs *regs);
 #endif
 
 #ifndef sys_fork
-asmlinkage long sys_fork(struct pt_regs *regs);
+asmlinkage long sys_fork(void);
 #endif
 
 #ifndef sys_vfork
-asmlinkage long sys_vfork(struct pt_regs *regs);
+asmlinkage long sys_vfork(void);
 #endif
 
 #ifndef sys_execve

kernel/fork.c

@@ -1645,6 +1645,49 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 }
 #endif
 
+#ifdef __ARCH_WANT_SYS_FORK
+SYSCALL_DEFINE0(fork)
+{
+#ifdef CONFIG_MMU
+	return do_fork(SIGCHLD, 0, current_pt_regs(), 0, NULL, NULL);
+#else
+	/* can not support in nommu mode */
+	return(-EINVAL);
+#endif
+}
+#endif
+
+#ifdef __ARCH_WANT_SYS_VFORK
+SYSCALL_DEFINE0(vfork)
+{
+	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, current_pt_regs(),
+			0, NULL, NULL);
+}
+#endif
+
+#ifdef __ARCH_WANT_SYS_CLONE
+#ifdef CONFIG_CLONE_BACKWARDS
+SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
+		 int __user *, parent_tidptr,
+		 int, tls_val,
+		 int __user *, child_tidptr)
+#elif defined(CONFIG_CLONE_BACKWARDS2)
+SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
+		 int __user *, parent_tidptr,
+		 int __user *, child_tidptr,
+		 int, tls_val)
+#else
+SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
+		 int __user *, parent_tidptr,
+		 int __user *, child_tidptr,
+		 int, tls_val)
+#endif
+{
+	return do_fork(clone_flags, newsp, current_pt_regs(), 0,
+		parent_tidptr, child_tidptr);
+}
+#endif
+
 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
 #define ARCH_MIN_MMSTRUCT_ALIGN 0
 #endif