xtensa: use generic tracehooks

Use tracehook_report_syscall_{entry,exit} instead of a local copy of it
in do_syscall_trace. Allow tracehook to cancel syscall by returning
invalid syscall number to the system_call function.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/kernel/entry.S

@@ -1899,10 +1899,11 @@ ENTRY(system_call)
 	movi	a4, do_syscall_trace_enter
 	s32i	a3, a2, PT_SYSCALL
 	callx4	a4
+	mov	a3, a6
 
 	/* syscall = sys_call_table[syscall_nr] */
 
-	movi	a4, sys_call_table;
+	movi	a4, sys_call_table
 	movi	a5, __NR_syscall_count
 	movi	a6, -ENOSYS
 	bgeu	a3, a5, 1f

arch/xtensa/kernel/ptrace.c

@@ -23,6 +23,7 @@
 #include <linux/security.h>
 #include <linux/signal.h>
 #include <linux/smp.h>
+#include <linux/tracehook.h>
 #include <linux/uaccess.h>
 
 #include <asm/coprocessor.h>
@@ -468,36 +469,21 @@ long arch_ptrace(struct task_struct *child, long request,
 	return ret;
 }
 
-void do_syscall_trace(void)
-{
-	/*
-	 * The 0x80 provides a way for the tracing parent to distinguish
-	 * between a syscall stop and SIGTRAP delivery
-	 */
-	ptrace_notify(SIGTRAP |
-		      ((current->ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
-
-	/*
-	 * this isn't the same as continuing with a signal, but it will do
-	 * for normal use.  strace only continues with a signal if the
-	 * stopping signal is not SIGTRAP.  -brl
-	 */
-	if (current->exit_code) {
-		send_sig(current->exit_code, current, 1);
-		current->exit_code = 0;
-	}
-}
-
-void do_syscall_trace_enter(struct pt_regs *regs)
+unsigned long do_syscall_trace_enter(struct pt_regs *regs)
 {
 	if (test_thread_flag(TIF_SYSCALL_TRACE) &&
-	    (current->ptrace & PT_PTRACED))
-		do_syscall_trace();
+	    tracehook_report_syscall_entry(regs))
+		return -1;
+
+	return regs->areg[2];
 }
 
 void do_syscall_trace_leave(struct pt_regs *regs)
 {
-	if (test_thread_flag(TIF_SYSCALL_TRACE) &&
-	    (current->ptrace & PT_PTRACED))
-		do_syscall_trace();
+	int step;
+
+	step = test_thread_flag(TIF_SINGLESTEP);
+
+	if (step || test_thread_flag(TIF_SYSCALL_TRACE))
+		tracehook_report_syscall_exit(regs, step);
 }