arm64: get rid of fork/vfork/clone wrappers

[fixes from Catalin Marinas folded]
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/arm64/include/asm/syscalls.h

@@ -23,15 +23,16 @@
 /*
  * System call wrappers implemented in kernel/entry.S.
  */
-asmlinkage long sys_clone_wrapper(unsigned long clone_flags,
-				  unsigned long newsp,
-				  void __user *parent_tid,
-				  unsigned long tls_val,
-				  void __user *child_tid);
 asmlinkage long sys_rt_sigreturn_wrapper(void);
 asmlinkage long sys_sigaltstack_wrapper(const stack_t __user *uss,
 					stack_t __user *uoss);
 
+/*
+ * AArch64 sys_clone implementation has a different prototype than the generic
+ * one (additional TLS value argument).
+ */
+#define sys_clone	sys_clone
+
 #include <asm-generic/syscalls.h>
 
 #endif	/* __ASM_SYSCALLS_H */

arch/arm64/include/asm/unistd32.h

@@ -23,7 +23,7 @@
 
 __SYSCALL(0,   sys_restart_syscall)
 __SYSCALL(1,   sys_exit)
-__SYSCALL(2,   compat_sys_fork_wrapper)
+__SYSCALL(2,   compat_sys_fork)
 __SYSCALL(3,   sys_read)
 __SYSCALL(4,   sys_write)
 __SYSCALL(5,   compat_sys_open)
@@ -141,7 +141,7 @@ __SYSCALL(116, compat_sys_sysinfo)
 __SYSCALL(117, sys_ni_syscall)			/* 117 was sys_ipc */
 __SYSCALL(118, sys_fsync)
 __SYSCALL(119, compat_sys_sigreturn_wrapper)
-__SYSCALL(120, compat_sys_clone_wrapper)
+__SYSCALL(120, sys_clone)
 __SYSCALL(121, sys_setdomainname)
 __SYSCALL(122, sys_newuname)
 __SYSCALL(123, sys_ni_syscall)			/* 123 was sys_modify_ldt */
@@ -211,7 +211,7 @@ __SYSCALL(186, compat_sys_sigaltstack_wrapper)
 __SYSCALL(187, compat_sys_sendfile)
 __SYSCALL(188, sys_ni_syscall)			/* 188 reserved */
 __SYSCALL(189, sys_ni_syscall)			/* 189 reserved */
-__SYSCALL(190, compat_sys_vfork_wrapper)
+__SYSCALL(190, compat_sys_vfork)
 __SYSCALL(191, compat_sys_getrlimit)		/* SuS compliant getrlimit */
 __SYSCALL(192, sys_mmap_pgoff)
 __SYSCALL(193, compat_sys_truncate64_wrapper)

arch/arm64/kernel/entry.S

@@ -676,11 +676,6 @@ __sys_trace_return:
 /*
  * Special system call wrappers.
  */
-ENTRY(sys_clone_wrapper)
-	mov	x5, sp
-	b	sys_clone
-ENDPROC(sys_clone_wrapper)
-
 ENTRY(sys_rt_sigreturn_wrapper)
 	mov	x0, sp
 	b	sys_rt_sigreturn

arch/arm64/kernel/process.c

@@ -246,14 +246,20 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 		*childregs = *regs;
 		childregs->regs[0] = 0;
 		if (is_compat_thread(task_thread_info(p))) {
-			childregs->compat_sp = stack_start;
+			if (stack_start)
+				childregs->compat_sp = stack_start;
 		} else {
 			/*
 			 * Read the current TLS pointer from tpidr_el0 as it may be
 			 * out-of-sync with the saved value.
 			 */
 			asm("mrs %0, tpidr_el0" : "=r" (tls));
-			childregs->sp = stack_start;
+			if (stack_start) {
+				/* 16-byte aligned stack mandatory on AArch64 */
+				if (stack_start & 15)
+					return -EINVAL;
+				childregs->sp = stack_start;
+			}
 		}
 		/*
 		 * If a TLS pointer was passed to clone (4th argument), use it

arch/arm64/kernel/sys.c

@@ -31,14 +31,10 @@
  */
 asmlinkage long sys_clone(unsigned long clone_flags, unsigned long newsp,
 			  int __user *parent_tidptr, unsigned long tls_val,
-			  int __user *child_tidptr, struct pt_regs *regs)
+			  int __user *child_tidptr)
 {
-	if (!newsp)
-		newsp = regs->sp;
-	/* 16-byte aligned stack mandatory on AArch64 */
-	if (newsp & 15)
-		return -EINVAL;
-	return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
+	return do_fork(clone_flags, newsp, current_pt_regs(), 0,
+			parent_tidptr, child_tidptr);
 }
 
 asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
@@ -54,7 +50,6 @@ asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
 /*
  * Wrappers to pass the pt_regs argument.
  */
-#define sys_clone		sys_clone_wrapper
 #define sys_rt_sigreturn	sys_rt_sigreturn_wrapper
 #define sys_sigaltstack		sys_sigaltstack_wrapper
 

arch/arm64/kernel/sys32.S

@@ -26,20 +26,6 @@
 /*
  * System call wrappers for the AArch32 compatibility layer.
  */
-compat_sys_fork_wrapper:
-	mov	x0, sp
-	b	compat_sys_fork
-ENDPROC(compat_sys_fork_wrapper)
-
-compat_sys_vfork_wrapper:
-	mov	x0, sp
-	b	compat_sys_vfork
-ENDPROC(compat_sys_vfork_wrapper)
-
-compat_sys_clone_wrapper:
-	mov	x5, sp
-	b	compat_sys_clone
-ENDPROC(compat_sys_clone_wrapper)
 
 compat_sys_sigreturn_wrapper:
 	mov	x0, sp

arch/arm64/kernel/sys_compat.c

@@ -28,25 +28,15 @@
 #include <asm/cacheflush.h>
 #include <asm/unistd32.h>
 
-asmlinkage int compat_sys_fork(struct pt_regs *regs)
+asmlinkage int compat_sys_fork(void)
 {
-	return do_fork(SIGCHLD, regs->compat_sp, regs, 0, NULL, NULL);
+	return do_fork(SIGCHLD, 0, current_pt_regs(), 0, NULL, NULL);
 }
 
-asmlinkage int compat_sys_clone(unsigned long clone_flags, unsigned long newsp,
-			  int __user *parent_tidptr, int tls_val,
-			  int __user *child_tidptr, struct pt_regs *regs)
+asmlinkage int compat_sys_vfork(void)
 {
-	if (!newsp)
-		newsp = regs->compat_sp;
-
-	return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
-}
-
-asmlinkage int compat_sys_vfork(struct pt_regs *regs)
-{
-	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->compat_sp,
-		       regs, 0, NULL, NULL);
+	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
+		       current_pt_regs(), 0, NULL, NULL);
 }
 
 asmlinkage int compat_sys_sched_rr_get_interval(compat_pid_t pid,