metag: Memory handling

Meta has instructions for accessing:
 - bytes        - GETB (1 byte)
 - words        - GETW (2 bytes)
 - doublewords  - GETD (4 bytes)
 - longwords    - GETL (8 bytes)

All accesses must be aligned. Unaligned accesses can be detected and
made to fault on Meta2, however it isn't possible to fix up unaligned
writes so we don't bother fixing up reads either.

This patch adds metag memory handling code including:
 - I/O memory (io.h, ioremap.c): Actually any virtual memory can be
   accessed with these helpers. A part of the non-MMUable address space
   is used for memory mapped I/O. The ioremap() function is implemented
   one to one for non-MMUable addresses.
 - User memory (uaccess.h, usercopy.c): User memory is directly
   accessible from privileged code.
 - Kernel memory (maccess.c): probe_kernel_write() needs to be
   overwridden to use the I/O functions when doing a simple aligned
   write to non-writecombined memory, otherwise the write may be split
   by the generic version.

Note that due to the fact that a portion of the virtual address space is
non-MMUable, and therefore always maps directly to the physical address
space, metag specific I/O functions are made available (metag_in32,
metag_out32 etc). These cast the address argument to a pointer so that
they can be used with raw physical addresses. These accessors are only
to be used for accessing fixed core Meta architecture registers in the
non-MMU region, and not for any SoC/peripheral registers.

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

1 files changed, 241 insertions, 0 deletions

diff --git a/arch/metag/include/asm/uaccess.h b/arch/metag/include/asm/uaccess.h
new file mode 100644
index 000000000000..0748b0a97986
--- /dev/null
+++ b/arch/metag/include/asm/uaccess.h
@@ -0,0 +1,241 @@
+#ifndef __METAG_UACCESS_H
+#define __METAG_UACCESS_H
+
+/*
+ * User space memory access functions
+ */
+#include <linux/sched.h>
+
+#define VERIFY_READ	0
+#define VERIFY_WRITE	1
+
+/*
+ * The fs value determines whether argument validity checking should be
+ * performed or not.  If get_fs() == USER_DS, checking is performed, with
+ * get_fs() == KERNEL_DS, checking is bypassed.
+ *
+ * For historical reasons, these macros are grossly misnamed.
+ */
+
+#define MAKE_MM_SEG(s)  ((mm_segment_t) { (s) })
+
+#define KERNEL_DS       MAKE_MM_SEG(0xFFFFFFFF)
+#define USER_DS		MAKE_MM_SEG(PAGE_OFFSET)
+
+#define get_ds()	(KERNEL_DS)
+#define get_fs()        (current_thread_info()->addr_limit)
+#define set_fs(x)       (current_thread_info()->addr_limit = (x))
+
+#define segment_eq(a, b)	((a).seg == (b).seg)
+
+#define __kernel_ok (segment_eq(get_fs(), KERNEL_DS))
+/*
+ * Explicitly allow NULL pointers here. Parts of the kernel such
+ * as readv/writev use access_ok to validate pointers, but want
+ * to allow NULL pointers for various reasons. NULL pointers are
+ * safe to allow through because the first page is not mappable on
+ * Meta.
+ *
+ * We also wish to avoid letting user code access the system area
+ * and the kernel half of the address space.
+ */
+#define __user_bad(addr, size) (((addr) > 0 && (addr) < META_MEMORY_BASE) || \
+				((addr) > PAGE_OFFSET &&		\
+				 (addr) < LINCORE_BASE))
+
+static inline int __access_ok(unsigned long addr, unsigned long size)
+{
+	return __kernel_ok || !__user_bad(addr, size);
+}
+
+#define access_ok(type, addr, size) __access_ok((unsigned long)(addr),	\
+						(unsigned long)(size))
+
+static inline int verify_area(int type, const void *addr, unsigned long size)
+{
+	return access_ok(type, addr, size) ? 0 : -EFAULT;
+}
+
+/*
+ * The exception table consists of pairs of addresses: the first is the
+ * address of an instruction that is allowed to fault, and the second is
+ * the address at which the program should continue.  No registers are
+ * modified, so it is entirely up to the continuation code to figure out
+ * what to do.
+ *
+ * All the routines below use bits of fixup code that are out of line
+ * with the main instruction path.  This means when everything is well,
+ * we don't even have to jump over them.  Further, they do not intrude
+ * on our cache or tlb entries.
+ */
+struct exception_table_entry {
+	unsigned long insn, fixup;
+};
+
+extern int fixup_exception(struct pt_regs *regs);
+
+/*
+ * These are the main single-value transfer routines.  They automatically
+ * use the right size if we just have the right pointer type.
+ */
+
+#define put_user(x, ptr) \
+	__put_user_check((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
+#define __put_user(x, ptr) \
+	__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
+
+extern void __put_user_bad(void);
+
+#define __put_user_nocheck(x, ptr, size)		\
+({                                                      \
+	long __pu_err;                                  \
+	__put_user_size((x), (ptr), (size), __pu_err);	\
+	__pu_err;                                       \
+})
+
+#define __put_user_check(x, ptr, size)				\
+({                                                              \
+	long __pu_err = -EFAULT;                                \
+	__typeof__(*(ptr)) __user *__pu_addr = (ptr);           \
+	if (access_ok(VERIFY_WRITE, __pu_addr, size))		\
+		__put_user_size((x), __pu_addr, (size), __pu_err);	\
+	__pu_err;                                               \
+})
+
+extern long __put_user_asm_b(unsigned int x, void __user *addr);
+extern long __put_user_asm_w(unsigned int x, void __user *addr);
+extern long __put_user_asm_d(unsigned int x, void __user *addr);
+extern long __put_user_asm_l(unsigned long long x, void __user *addr);
+
+#define __put_user_size(x, ptr, size, retval)			\
+do {                                                            \
+	retval = 0;                                             \
+	switch (size) {                                         \
+	case 1:								\
+		retval = __put_user_asm_b((unsigned int)x, ptr); break;	\
+	case 2:								\
+		retval = __put_user_asm_w((unsigned int)x, ptr); break;	\
+	case 4:								\
+		retval = __put_user_asm_d((unsigned int)x, ptr); break;	\
+	case 8:								\
+		retval = __put_user_asm_l((unsigned long long)x, ptr); break; \
+	default:							\
+		__put_user_bad();					\
+	}								\
+} while (0)
+
+#define get_user(x, ptr) \
+	__get_user_check((x), (ptr), sizeof(*(ptr)))
+#define __get_user(x, ptr) \
+	__get_user_nocheck((x), (ptr), sizeof(*(ptr)))
+
+extern long __get_user_bad(void);
+
+#define __get_user_nocheck(x, ptr, size)			\
+({                                                              \
+	long __gu_err, __gu_val;                                \
+	__get_user_size(__gu_val, (ptr), (size), __gu_err);	\
+	(x) = (__typeof__(*(ptr)))__gu_val;                     \
+	__gu_err;                                               \
+})
+
+#define __get_user_check(x, ptr, size)					\
+({                                                                      \
+	long __gu_err = -EFAULT, __gu_val = 0;                          \
+	const __typeof__(*(ptr)) __user *__gu_addr = (ptr);		\
+	if (access_ok(VERIFY_READ, __gu_addr, size))			\
+		__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
+	(x) = (__typeof__(*(ptr)))__gu_val;                             \
+	__gu_err;                                                       \
+})
+
+extern unsigned char __get_user_asm_b(const void __user *addr, long *err);
+extern unsigned short __get_user_asm_w(const void __user *addr, long *err);
+extern unsigned int __get_user_asm_d(const void __user *addr, long *err);
+
+#define __get_user_size(x, ptr, size, retval)			\
+do {                                                            \
+	retval = 0;                                             \
+	switch (size) {                                         \
+	case 1:							\
+		x = __get_user_asm_b(ptr, &retval); break;	\
+	case 2:							\
+		x = __get_user_asm_w(ptr, &retval); break;	\
+	case 4:							\
+		x = __get_user_asm_d(ptr, &retval); break;	\
+	default:						\
+		(x) = __get_user_bad();				\
+	}                                                       \
+} while (0)
+
+/*
+ * Copy a null terminated string from userspace.
+ *
+ * Must return:
+ * -EFAULT		for an exception
+ * count		if we hit the buffer limit
+ * bytes copied		if we hit a null byte
+ * (without the null byte)
+ */
+
+extern long __must_check __strncpy_from_user(char *dst, const char __user *src,
+					     long count);
+
+#define strncpy_from_user(dst, src, count) __strncpy_from_user(dst, src, count)
+
+/*
+ * Return the size of a string (including the ending 0)
+ *
+ * Return 0 on exception, a value greater than N if too long
+ */
+extern long __must_check strnlen_user(const char __user *src, long count);
+
+#define strlen_user(str) strnlen_user(str, 32767)
+
+extern unsigned long __must_check __copy_user_zeroing(void *to,
+						      const void __user *from,
+						      unsigned long n);
+
+static inline unsigned long
+copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+	if (access_ok(VERIFY_READ, from, n))
+		return __copy_user_zeroing(to, from, n);
+	return n;
+}
+
+#define __copy_from_user(to, from, n) __copy_user_zeroing(to, from, n)
+#define __copy_from_user_inatomic __copy_from_user
+
+extern unsigned long __must_check __copy_user(void __user *to,
+					      const void *from,
+					      unsigned long n);
+
+static inline unsigned long copy_to_user(void __user *to, const void *from,
+					 unsigned long n)
+{
+	if (access_ok(VERIFY_WRITE, to, n))
+		return __copy_user(to, from, n);
+	return n;
+}
+
+#define __copy_to_user(to, from, n) __copy_user(to, from, n)
+#define __copy_to_user_inatomic __copy_to_user
+
+/*
+ * Zero Userspace
+ */
+
+extern unsigned long __must_check __do_clear_user(void __user *to,
+						  unsigned long n);
+
+static inline unsigned long clear_user(void __user *to, unsigned long n)
+{
+	if (access_ok(VERIFY_WRITE, to, n))
+		return __do_clear_user(to, n);
+	return n;
+}
+
+#define __clear_user(to, n)            __do_clear_user(to, n)
+
+#endif /* _METAG_UACCESS_H */