ptrace: Remove the unnecessary arguments from arch_ptrace_stop

Both arch_ptrace_stop_needed and arch_ptrace_stop are called with an
exit_code and a siginfo structure.  Neither argument is used by any of
the implementations so just remove the unneeded arguments.

The two arechitectures that implement arch_ptrace_stop are ia64 and
sparc.  Both architectures flush their register stacks before a
ptrace_stack so that all of the register information can be accessed
by debuggers.

As the question of if a register stack needs to be flushed is
independent of why ptrace is stopping not needing arguments make sense.

Cc: David Miller <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Link: https://lkml.kernel.org/r/87lf3mx290.fsf@disp2133
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

arch/ia64/include/asm/ptrace.h

@@ -129,9 +129,9 @@ static inline long regs_return_value(struct pt_regs *regs)
   extern void ia64_decrement_ip (struct pt_regs *pt);
 
   extern void ia64_ptrace_stop(void);
-  #define arch_ptrace_stop(code, info) \
+  #define arch_ptrace_stop() \
 	ia64_ptrace_stop()
-  #define arch_ptrace_stop_needed(code, info) \
+  #define arch_ptrace_stop_needed() \
 	(!test_thread_flag(TIF_RESTORE_RSE))
 
   extern void ptrace_attach_sync_user_rbs (struct task_struct *);

arch/sparc/include/asm/ptrace.h

@@ -26,12 +26,12 @@ static inline bool pt_regs_clear_syscall(struct pt_regs *regs)
 	return (regs->tstate &= ~TSTATE_SYSCALL);
 }
 
-#define arch_ptrace_stop_needed(exit_code, info) \
+#define arch_ptrace_stop_needed() \
 ({	flush_user_windows(); \
 	get_thread_wsaved() != 0; \
 })
 
-#define arch_ptrace_stop(exit_code, info) \
+#define arch_ptrace_stop() \
 	synchronize_user_stack()
 
 #define current_pt_regs() \
@@ -129,12 +129,12 @@ static inline bool pt_regs_clear_syscall(struct pt_regs *regs)
 	return (regs->psr &= ~PSR_SYSCALL);
 }
 
-#define arch_ptrace_stop_needed(exit_code, info) \
+#define arch_ptrace_stop_needed() \
 ({	flush_user_windows(); \
 	current_thread_info()->w_saved != 0;	\
 })
 
-#define arch_ptrace_stop(exit_code, info) \
+#define arch_ptrace_stop() \
 	synchronize_user_stack()
 
 #define current_pt_regs() \

include/linux/ptrace.h

@@ -362,29 +362,25 @@ static inline void user_single_step_report(struct pt_regs *regs)
 #ifndef arch_ptrace_stop_needed
 /**
  * arch_ptrace_stop_needed - Decide whether arch_ptrace_stop() should be called
- * @code:	current->exit_code value ptrace will stop with
- * @info:	siginfo_t pointer (or %NULL) for signal ptrace will stop with
  *
  * This is called with the siglock held, to decide whether or not it's
- * necessary to release the siglock and call arch_ptrace_stop() with the
+ * necessary to release the siglock and call arch_ptrace_stop().  It can be
- * same @code and @info arguments.  It can be defined to a constant if
+ * defined to a constant if arch_ptrace_stop() is never required, or always
- * arch_ptrace_stop() is never required, or always is.  On machines where
+ * is.  On machines where this makes sense, it should be defined to a quick
- * this makes sense, it should be defined to a quick test to optimize out
+ * test to optimize out calling arch_ptrace_stop() when it would be
- * calling arch_ptrace_stop() when it would be superfluous.  For example,
+ * superfluous.  For example, if the thread has not been back to user mode
- * if the thread has not been back to user mode since the last stop, the
+ * since the last stop, the thread state might indicate that nothing needs
- * thread state might indicate that nothing needs to be done.
+ * to be done.
  *
  * This is guaranteed to be invoked once before a task stops for ptrace and
  * may include arch-specific operations necessary prior to a ptrace stop.
  */
-#define arch_ptrace_stop_needed(code, info)	(0)
+#define arch_ptrace_stop_needed()	(0)
 #endif
 
 #ifndef arch_ptrace_stop
 /**
  * arch_ptrace_stop - Do machine-specific work before stopping for ptrace
- * @code:	current->exit_code value ptrace will stop with
- * @info:	siginfo_t pointer (or %NULL) for signal ptrace will stop with
  *
  * This is called with no locks held when arch_ptrace_stop_needed() has
  * just returned nonzero.  It is allowed to block, e.g. for user memory
@@ -394,7 +390,7 @@ static inline void user_single_step_report(struct pt_regs *regs)
  * we only do it when the arch requires it for this particular stop, as
  * indicated by arch_ptrace_stop_needed().
  */
-#define arch_ptrace_stop(code, info)		do { } while (0)
+#define arch_ptrace_stop()		do { } while (0)
 #endif
 
 #ifndef current_pt_regs

kernel/signal.c

@@ -2200,7 +2200,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 {
 	bool gstop_done = false;
 
-	if (arch_ptrace_stop_needed(exit_code, info)) {
+	if (arch_ptrace_stop_needed()) {
 		/*
 		 * The arch code has something special to do before a
 		 * ptrace stop.  This is allowed to block, e.g. for faults
@@ -2210,7 +2210,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 		 * any signal bookkeeping like checking group_stop_count.
 		 */
 		spin_unlock_irq(&current->sighand->siglock);
-		arch_ptrace_stop(exit_code, info);
+		arch_ptrace_stop();
 		spin_lock_irq(&current->sighand->siglock);
 	}