powerpc: Add asm/syscall.h with the tracehook entry points

Add asm/syscall.h for powerpc with all the required entry points.
This will allow arch-independent tracing code for system calls.

BenH: Fixed up use of regs->trap to properly mask low bit
Signed-off-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

include/asm-powerpc/ptrace.h

@@ -84,6 +84,7 @@ struct pt_regs {
 #ifndef __ASSEMBLY__
 
 #define instruction_pointer(regs) ((regs)->nip)
+#define user_stack_pointer(regs) ((regs)->gpr[1])
 #define regs_return_value(regs) ((regs)->gpr[3])
 
 #ifdef CONFIG_SMP

include/asm-powerpc/syscall.h

+/*
+ * Access to user system call parameters and results
+ *
+ * Copyright (C) 2008 Red Hat, Inc.  All rights reserved.
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU General Public License v.2.
+ *
+ * See asm-generic/syscall.h for descriptions of what we must do here.
+ */
+
+#ifndef _ASM_SYSCALL_H
+#define _ASM_SYSCALL_H	1
+
+#include <linux/sched.h>
+
+static inline long syscall_get_nr(struct task_struct *task,
+				  struct pt_regs *regs)
+{
+	return TRAP(regs) == 0xc00 ? regs->gpr[0] : -1L;
+}
+
+static inline void syscall_rollback(struct task_struct *task,
+				    struct pt_regs *regs)
+{
+	regs->gpr[3] = regs->orig_gpr3;
+}
+
+static inline long syscall_get_error(struct task_struct *task,
+				     struct pt_regs *regs)
+{
+	return (regs->ccr & 0x1000) ? -regs->gpr[3] : 0;
+}
+
+static inline long syscall_get_return_value(struct task_struct *task,
+					    struct pt_regs *regs)
+{
+	return regs->gpr[3];
+}
+
+static inline void syscall_set_return_value(struct task_struct *task,
+					    struct pt_regs *regs,
+					    int error, long val)
+{
+	if (error) {
+		regs->ccr |= 0x1000L;
+		regs->gpr[3] = -error;
+	} else {
+		regs->ccr &= ~0x1000L;
+		regs->gpr[3] = val;
+	}
+}
+
+static inline void syscall_get_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned int i, unsigned int n,
+					 unsigned long *args)
+{
+	BUG_ON(i + n > 6);
+#ifdef CONFIG_PPC64
+	if (test_tsk_thread_flag(task, TIF_32BIT)) {
+		/*
+		 * Zero-extend 32-bit argument values.  The high bits are
+		 * garbage ignored by the actual syscall dispatch.
+		 */
+		while (n-- > 0)
+			args[n] = (u32) regs->gpr[3 + i + n];
+		return;
+	}
+#endif
+	memcpy(args, &regs->gpr[3 + i], n * sizeof(args[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)
+{
+	BUG_ON(i + n > 6);
+	memcpy(&regs->gpr[3 + i], args, n * sizeof(args[0]));
+}
+
+#endif	/* _ASM_SYSCALL_H */