c6x: sanitize copy_thread(), get rid of clone(2) wrapper, switch to generic clone()

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

arch/c6x/include/asm/syscalls.h

@@ -41,10 +41,6 @@ extern long sys_fallocate_c6x(int fd, int mode,
 			      u32 len_lo, u32 len_hi);
 extern int sys_cache_sync(unsigned long s, unsigned long e);
 
-struct pt_regs;
-
-extern asmlinkage long sys_c6x_clone(struct pt_regs *regs);
-
 #include <asm-generic/syscalls.h>
 
 #endif /* __ASM_C6X_SYSCALLS_H */

arch/c6x/include/uapi/asm/unistd.h

@@ -15,6 +15,7 @@
  */
 
 #define __ARCH_WANT_SYS_EXECVE
+#define __ARCH_WANT_SYS_CLONE
 
 /* Use the standard ABI for syscalls. */
 #include <asm-generic/unistd.h>

arch/c6x/kernel/entry.S

@@ -613,18 +613,6 @@ ENDPROC(sys_sigaltstack)
 	;; Special system calls
 	;; return address is in B3
 	;;
-ENTRY(sys_clone)
-	ADD	.D1X	SP,8,A4
-#ifdef CONFIG_C6X_BIG_KERNEL
- ||	MVKL	.S1	sys_c6x_clone,A0
-	MVKH	.S1	sys_c6x_clone,A0
-	BNOP	.S2X	A0,5
-#else
- ||	B	.S2	sys_c6x_clone
-	NOP	5
-#endif
-ENDPROC(sys_clone)
-
 ENTRY(sys_rt_sigreturn)
 	ADD	.D1X	SP,8,A4
 #ifdef CONFIG_C6X_BIG_KERNEL

arch/c6x/kernel/process.c

@@ -112,22 +112,6 @@ void exit_thread(void)
 {
 }
 
-SYSCALL_DEFINE1(c6x_clone, struct pt_regs *, regs)
-{
-	unsigned long clone_flags;
-	unsigned long newsp;
-
-	/* syscall puts clone_flags in A4 and usp in B4 */
-	clone_flags = regs->orig_a4;
-	if (regs->b4)
-		newsp = regs->b4;
-	else
-		newsp = regs->sp;
-
-	return do_fork(clone_flags, newsp, regs, 0, (int __user *)regs->a6,
-		       (int __user *)regs->b6);
-}
-
 /*
  * Do necessary setup to start up a newly executed thread.
  */
@@ -155,13 +139,13 @@ void start_thread(struct pt_regs *regs, unsigned int pc, unsigned long usp)
  */
 int copy_thread(unsigned long clone_flags, unsigned long usp,
 		unsigned long ustk_size,
-		struct task_struct *p, struct pt_regs *regs)
+		struct task_struct *p, struct pt_regs *unused)
 {
 	struct pt_regs *childregs;
 
 	childregs = task_pt_regs(p);
 
-	if (!regs) {
+	if (unlikely(p->flags & PF_KTHREAD)) {
 		/* case of  __kernel_thread: we return to supervisor space */
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->sp = (unsigned long)(childregs + 1);
@@ -170,7 +154,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 		childregs->a1 = ustk_size;	/* argument */
 	} else {
 		/* Otherwise use the given stack */
-		*childregs = *regs;
+		*childregs = *current_pt_regs();
+		if (usp)
 			childregs->sp = usp;
 		p->thread.pc = (unsigned long) ret_from_fork;
 	}