metag: System Calls

Add metag system call and gateway page interfaces. The metag
architecture port uses the generic system call numbers from
asm-generic/unistd.h, as well as a user gateway page mapped at
0x6ffff000 which contains fast atomic primitives (depending on SMP) and
a fast method of accessing TLS data.

System calls use the SWITCH instruction with the immediate 0x440001 to
signal a system call.

Signed-off-by: James Hogan <james.hogan@imgtec.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/arch/metag/include/asm/syscall.h b/arch/metag/include/asm/syscall.h
new file mode 100644
index 000000000000..24fc97939f77
--- /dev/null
+++ b/arch/metag/include/asm/syscall.h
@@ -0,0 +1,104 @@
+/*
+ * Access to user system call parameters and results
+ *
+ * Copyright (C) 2008 Imagination Technologies Ltd.
+ *
+ * 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_METAG_SYSCALL_H
+#define _ASM_METAG_SYSCALL_H
+
+#include <linux/sched.h>
+#include <linux/err.h>
+#include <linux/uaccess.h>
+
+#include <asm/switch.h>
+
+static inline long syscall_get_nr(struct task_struct *task,
+				  struct pt_regs *regs)
+{
+	unsigned long insn;
+
+	/*
+	 * FIXME there's no way to find out how we got here other than to
+	 * examine the memory at the PC to see if it is a syscall
+	 * SWITCH instruction.
+	 */
+	if (get_user(insn, (unsigned long *)(regs->ctx.CurrPC - 4)))
+		return -1;
+
+	if (insn == __METAG_SW_ENCODING(SYS))
+		return regs->ctx.DX[0].U1;
+	else
+		return -1L;
+}
+
+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)
+{
+	unsigned long error = regs->ctx.DX[0].U0;
+	return IS_ERR_VALUE(error) ? error : 0;
+}
+
+static inline long syscall_get_return_value(struct task_struct *task,
+					    struct pt_regs *regs)
+{
+	return regs->ctx.DX[0].U0;
+}
+
+static inline void syscall_set_return_value(struct task_struct *task,
+					    struct pt_regs *regs,
+					    int error, long val)
+{
+	regs->ctx.DX[0].U0 = (long) error ?: val;
+}
+
+static inline void syscall_get_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned int i, unsigned int n,
+					 unsigned long *args)
+{
+	unsigned int reg, j;
+	BUG_ON(i + n > 6);
+
+	for (j = i, reg = 6 - i; j < (i + n); j++, reg--) {
+		if (reg % 2)
+			args[j] = regs->ctx.DX[(reg + 1) / 2].U0;
+		else
+			args[j] = regs->ctx.DX[reg / 2].U1;
+	}
+}
+
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned int i, unsigned int n,
+					 const unsigned long *args)
+{
+	unsigned int reg;
+	BUG_ON(i + n > 6);
+
+	for (reg = 6 - i; i < (i + n); i++, reg--) {
+		if (reg % 2)
+			regs->ctx.DX[(reg + 1) / 2].U0 = args[i];
+		else
+			regs->ctx.DX[reg / 2].U1 = args[i];
+	}
+}
+
+#define NR_syscalls __NR_syscalls
+
+/* generic syscall table */
+extern const void *sys_call_table[];
+
+#endif	/* _ASM_METAG_SYSCALL_H */