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>

arch/metag/include/asm/mman.h

@@ -0,0 +1,11 @@
+#ifndef __METAG_MMAN_H__
+#define __METAG_MMAN_H__
+
+#include <uapi/asm/mman.h>
+
+#ifndef __ASSEMBLY__
+#define arch_mmap_check metag_mmap_check
+int metag_mmap_check(unsigned long addr, unsigned long len,
+		     unsigned long flags);
+#endif
+#endif /* __METAG_MMAN_H__ */

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 */

arch/metag/include/asm/syscalls.h

@@ -0,0 +1,39 @@
+#ifndef _ASM_METAG_SYSCALLS_H
+#define _ASM_METAG_SYSCALLS_H
+
+#include <linux/compiler.h>
+#include <linux/linkage.h>
+#include <linux/types.h>
+#include <linux/signal.h>
+
+/* kernel/signal.c */
+#define sys_rt_sigreturn sys_rt_sigreturn
+asmlinkage long sys_rt_sigreturn(void);
+
+#include <asm-generic/syscalls.h>
+
+/* kernel/sys_metag.c */
+asmlinkage int sys_metag_setglobalbit(char __user *, int);
+asmlinkage void sys_metag_set_fpu_flags(unsigned int);
+asmlinkage int sys_metag_set_tls(void __user *);
+asmlinkage void *sys_metag_get_tls(void);
+
+asmlinkage long sys_truncate64_metag(const char __user *, unsigned long,
+				     unsigned long);
+asmlinkage long sys_ftruncate64_metag(unsigned int, unsigned long,
+				      unsigned long);
+asmlinkage long sys_fadvise64_64_metag(int, unsigned long, unsigned long,
+				       unsigned long, unsigned long, int);
+asmlinkage long sys_readahead_metag(int, unsigned long, unsigned long, size_t);
+asmlinkage ssize_t sys_pread64_metag(unsigned long, char __user *, size_t,
+				     unsigned long, unsigned long);
+asmlinkage ssize_t sys_pwrite64_metag(unsigned long, char __user *, size_t,
+				      unsigned long, unsigned long);
+asmlinkage long sys_sync_file_range_metag(int, unsigned long, unsigned long,
+					  unsigned long, unsigned long,
+					  unsigned int);
+
+int do_work_pending(struct pt_regs *regs, unsigned int thread_flags,
+		    int syscall);
+
+#endif /* _ASM_METAG_SYSCALLS_H */

arch/metag/include/asm/unistd.h

@@ -0,0 +1,12 @@
+/*
+ * Copyright (C) 2012 Imagination Technologies Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <uapi/asm/unistd.h>
+
+#define __ARCH_WANT_SYS_CLONE

arch/metag/include/asm/user_gateway.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2010 Imagination Technologies
+ */
+
+#ifndef __ASM_METAG_USER_GATEWAY_H
+#define __ASM_METAG_USER_GATEWAY_H
+
+#include <asm/page.h>
+
+/* Page of kernel code accessible to userspace. */
+#define USER_GATEWAY_PAGE	0x6ffff000
+/* Offset of TLS pointer array in gateway page. */
+#define USER_GATEWAY_TLS	0x100
+
+#ifndef __ASSEMBLY__
+
+extern char __user_gateway_start;
+extern char __user_gateway_end;
+
+/* Kernel mapping of the gateway page. */
+extern void *gateway_page;
+
+static inline void set_gateway_tls(void __user *tls_ptr)
+{
+	void **gateway_tls = (void **)(gateway_page + USER_GATEWAY_TLS +
+				       hard_processor_id() * 4);
+
+	*gateway_tls = (__force void *)tls_ptr;
+#ifdef CONFIG_METAG_META12
+	/* Avoid cache aliases on virtually tagged cache. */
+	__builtin_dcache_flush((void *)USER_GATEWAY_PAGE + USER_GATEWAY_TLS +
+				       hard_processor_id() * sizeof(void *));
+#endif
+}
+
+extern int __kuser_get_tls(void);
+extern char *__kuser_get_tls_end[];
+
+extern int __kuser_cmpxchg(int, int, unsigned long *);
+extern char *__kuser_cmpxchg_end[];
+
+#endif
+
+#endif

arch/metag/include/uapi/asm/unistd.h

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2012 Imagination Technologies Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+/* Use the standard ABI for syscalls. */
+#include <asm-generic/unistd.h>
+
+/* metag-specific syscalls. */
+#define __NR_metag_setglobalbit		(__NR_arch_specific_syscall + 1)
+__SYSCALL(__NR_metag_setglobalbit, sys_metag_setglobalbit)
+#define __NR_metag_set_fpu_flags	(__NR_arch_specific_syscall + 2)
+__SYSCALL(__NR_metag_set_fpu_flags, sys_metag_set_fpu_flags)
+#define __NR_metag_set_tls		(__NR_arch_specific_syscall + 3)
+__SYSCALL(__NR_metag_set_tls, sys_metag_set_tls)
+#define __NR_metag_get_tls		(__NR_arch_specific_syscall + 4)
+__SYSCALL(__NR_metag_get_tls, sys_metag_get_tls)