seccomp: simplify secure_computing()

Afaict, the struct seccomp_data argument to secure_computing() is unused
by all current callers. So let's remove it.
The argument was added in [1]. It was added because having the arch
supply the syscall arguments used to be faster than having it done by
secure_computing() (cf. Andy's comment in [2]). This is not true anymore
though.

/* References */
[1]: 2f275de5 ("seccomp: Add a seccomp_data parameter secure_computing()")
[2]: https://lore.kernel.org/r/CALCETrU_fs_At-hTpr231kpaAd0z7xJN4ku-DvzhRU6cvcJA_w@mail.gmail.comSigned-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-parisc@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linux-um@lists.infradead.org
Cc: x86@kernel.org
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20190924064420.6353-1-christian.brauner@ubuntu.comSigned-off-by: Kees Cook <keescook@chromium.org>

arch/arm/kernel/ptrace.c

@@ -923,7 +923,7 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
 
 	/* Do seccomp after ptrace; syscall may have changed. */
 #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
-	if (secure_computing(NULL) == -1)
+	if (secure_computing() == -1)
 		return -1;
 #else
 	/* XXX: remove this once OABI gets fixed */

arch/arm64/kernel/ptrace.c

@@ -1816,7 +1816,7 @@ int syscall_trace_enter(struct pt_regs *regs)
 	}
 
 	/* Do the secure computing after ptrace; failures should be fast. */
-	if (secure_computing(NULL) == -1)
+	if (secure_computing() == -1)
 		return -1;
 
 	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))

arch/parisc/kernel/ptrace.c

@@ -342,7 +342,7 @@ long do_syscall_trace_enter(struct pt_regs *regs)
 	}
 
 	/* Do the secure computing check after ptrace. */
-	if (secure_computing(NULL) == -1)
+	if (secure_computing() == -1)
 		return -1;
 
 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS

arch/s390/kernel/ptrace.c

@@ -856,7 +856,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
 	}
 
 	/* Do the secure computing check after ptrace. */
-	if (secure_computing(NULL)) {
+	if (secure_computing()) {
 		/* seccomp failures shouldn't expose any additional code. */
 		return -1;
 	}

arch/um/kernel/skas/syscall.c

@@ -35,7 +35,7 @@ void handle_syscall(struct uml_pt_regs *r)
 		goto out;
 
 	/* Do the seccomp check after ptrace; failures should be fast. */
-	if (secure_computing(NULL) == -1)
+	if (secure_computing() == -1)
 		goto out;
 
 	syscall = UPT_SYSCALL_NR(r);

arch/x86/entry/vsyscall/vsyscall_64.c

@@ -222,7 +222,7 @@ bool emulate_vsyscall(unsigned long error_code,
 	 */
 	regs->orig_ax = syscall_nr;
 	regs->ax = -ENOSYS;
-	tmp = secure_computing(NULL);
+	tmp = secure_computing();
 	if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
 		warn_bad_vsyscall(KERN_DEBUG, regs,
 				  "seccomp tried to change syscall nr or ip");

include/linux/seccomp.h

@@ -33,10 +33,10 @@ struct seccomp {
 
 #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
 extern int __secure_computing(const struct seccomp_data *sd);
-static inline int secure_computing(const struct seccomp_data *sd)
+static inline int secure_computing(void)
 {
 	if (unlikely(test_thread_flag(TIF_SECCOMP)))
-		return  __secure_computing(sd);
+		return  __secure_computing(NULL);
 	return 0;
 }
 #else
@@ -59,7 +59,7 @@ struct seccomp { };
 struct seccomp_filter { };
 
 #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
-static inline int secure_computing(struct seccomp_data *sd) { return 0; }
+static inline int secure_computing(void) { return 0; }
 #else
 static inline void secure_computing_strict(int this_syscall) { return; }
 #endif