xtensa: implement tracehook functions and enable HAVE_ARCH_TRACEHOOK

Implement syscall_get_nr, syscall_rollback, syscall_get_error,
syscall_{get,set}_return_value and syscall_{get,set}_arguments.
Select HAVE_ARCH_TRACEHOOK as Xtensa now has all support for that.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -18,6 +18,7 @@ config XTENSA
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_STRNCPY_FROM_USER if KASAN
 	select HAVE_ARCH_KASAN if MMU
+	select HAVE_ARCH_TRACEHOOK
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_EXIT_THREAD

arch/xtensa/include/asm/syscall.h

@@ -10,6 +10,8 @@
 #ifndef _ASM_SYSCALL_H
 #define _ASM_SYSCALL_H
 
+#include <linux/err.h>
+#include <asm/ptrace.h>
 #include <uapi/linux/audit.h>
 
 static inline int syscall_get_arch(void)
@@ -17,7 +19,83 @@ static inline int syscall_get_arch(void)
 	return AUDIT_ARCH_XTENSA;
 }
 
-struct pt_regs;
+static inline long syscall_get_nr(struct task_struct *task,
+				  struct pt_regs *regs)
+{
+	return regs->syscall;
+}
+
+static inline void syscall_rollback(struct task_struct *task,
+				    struct pt_regs *regs)
+{
+	/* Do nothing. */
+}
+
+static inline long syscall_get_error(struct task_struct *task,
+				     struct pt_regs *regs)
+{
+	/* 0 if syscall succeeded, otherwise -Errorcode */
+	return IS_ERR_VALUE(regs->areg[2]) ? regs->areg[2] : 0;
+}
+
+static inline long syscall_get_return_value(struct task_struct *task,
+					    struct pt_regs *regs)
+{
+	return regs->areg[2];
+}
+
+static inline void syscall_set_return_value(struct task_struct *task,
+					    struct pt_regs *regs,
+					    int error, long val)
+{
+	regs->areg[0] = (long) error ? error : val;
+}
+
+#define SYSCALL_MAX_ARGS 6
+#define XTENSA_SYSCALL_ARGUMENT_REGS {6, 3, 4, 5, 8, 9}
+
+static inline void syscall_get_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned int i, unsigned int n,
+					 unsigned long *args)
+{
+	static const unsigned int reg[] = XTENSA_SYSCALL_ARGUMENT_REGS;
+	unsigned int j;
+
+	if (n == 0)
+		return;
+
+	WARN_ON_ONCE(i + n > SYSCALL_MAX_ARGS);
+
+	for (j = 0; j < n; ++j) {
+		if (i + j < SYSCALL_MAX_ARGS)
+			args[j] = regs->areg[reg[i + j]];
+		else
+			args[j] = 0;
+	}
+}
+
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned int i, unsigned int n,
+					 const unsigned long *args)
+{
+	static const unsigned int reg[] = XTENSA_SYSCALL_ARGUMENT_REGS;
+	unsigned int j;
+
+	if (n == 0)
+		return;
+
+	if (WARN_ON_ONCE(i + n > SYSCALL_MAX_ARGS)) {
+		if (i < SYSCALL_MAX_ARGS)
+			n = SYSCALL_MAX_ARGS - i;
+		else
+			return;
+	}
+
+	for (j = 0; j < n; ++j)
+		regs->areg[reg[i + j]] = args[j];
+}
 
 asmlinkage long xtensa_rt_sigreturn(struct pt_regs*);
 asmlinkage long xtensa_shmat(int, char __user *, int);