csky: User access

The patch adds "user access from kernel" codes.
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

arch/csky/lib/usercopy.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/uaccess.h>
+#include <linux/types.h>
+
+unsigned long raw_copy_from_user(void *to, const void *from,
+			unsigned long n)
+{
+	if (access_ok(VERIFY_READ, from, n))
+		__copy_user_zeroing(to, from, n);
+	else
+		memset(to, 0, n);
+	return n;
+}
+EXPORT_SYMBOL(raw_copy_from_user);
+
+unsigned long raw_copy_to_user(void *to, const void *from,
+			unsigned long n)
+{
+	if (access_ok(VERIFY_WRITE, to, n))
+		__copy_user(to, from, n);
+	return n;
+}
+EXPORT_SYMBOL(raw_copy_to_user);
+
+
+/*
+ * copy a null terminated string from userspace.
+ */
+#define __do_strncpy_from_user(dst, src, count, res)	\
+do {							\
+	int tmp;					\
+	long faultres;					\
+	asm volatile(					\
+	"       cmpnei  %3, 0           \n"		\
+	"       bf      4f              \n"		\
+	"1:     cmpnei  %1, 0          	\n"		\
+	"       bf      5f              \n"		\
+	"2:     ldb     %4, (%3, 0)     \n"		\
+	"       stb     %4, (%2, 0)     \n"		\
+	"       cmpnei  %4, 0           \n"		\
+	"       bf      3f              \n"		\
+	"       addi    %3,  1          \n"		\
+	"       addi    %2,  1          \n"		\
+	"       subi    %1,  1          \n"		\
+	"       br      1b              \n"		\
+	"3:     subu	%0, %1          \n"		\
+	"       br      5f              \n"		\
+	"4:     mov     %0, %5          \n"		\
+	"       br      5f              \n"		\
+	".section __ex_table, \"a\"     \n"		\
+	".align   2                     \n"		\
+	".long    2b, 4b                \n"		\
+	".previous                      \n"		\
+	"5:                             \n"		\
+	: "=r"(res), "=r"(count), "=r"(dst),		\
+	  "=r"(src), "=r"(tmp),   "=r"(faultres)	\
+	: "5"(-EFAULT), "0"(count), "1"(count),		\
+	  "2"(dst), "3"(src)				\
+	: "memory", "cc");				\
+} while (0)
+
+/*
+ * __strncpy_from_user: - Copy a NUL terminated string from userspace,
+ * with less checking.
+ * @dst:   Destination address, in kernel space.  This buffer must be at
+ *         least @count bytes long.
+ * @src:   Source address, in user space.
+ * @count: Maximum number of bytes to copy, including the trailing NUL.
+ *
+ * Copies a NUL-terminated string from userspace to kernel space.
+ * Caller must check the specified block with access_ok() before calling
+ * this function.
+ *
+ * On success, returns the length of the string (not including the trailing
+ * NUL).
+ *
+ * If access to userspace fails, returns -EFAULT (some data may have been
+ * copied).
+ *
+ * If @count is smaller than the length of the string, copies @count bytes
+ * and returns @count.
+ */
+long __strncpy_from_user(char *dst, const char *src, long count)
+{
+	long res;
+
+	__do_strncpy_from_user(dst, src, count, res);
+	return res;
+}
+EXPORT_SYMBOL(__strncpy_from_user);
+
+/*
+ * strncpy_from_user: - Copy a NUL terminated string from userspace.
+ * @dst:   Destination address, in kernel space.  This buffer must be at
+ *         least @count bytes long.
+ * @src:   Source address, in user space.
+ * @count: Maximum number of bytes to copy, including the trailing NUL.
+ *
+ * Copies a NUL-terminated string from userspace to kernel space.
+ *
+ * On success, returns the length of the string (not including the trailing
+ * NUL).
+ *
+ * If access to userspace fails, returns -EFAULT (some data may have been
+ * copied).
+ *
+ * If @count is smaller than the length of the string, copies @count bytes
+ * and returns @count.
+ */
+long strncpy_from_user(char *dst, const char *src, long count)
+{
+	long res = -EFAULT;
+
+	if (access_ok(VERIFY_READ, src, 1))
+		__do_strncpy_from_user(dst, src, count, res);
+	return res;
+}
+EXPORT_SYMBOL(strncpy_from_user);
+
+/*
+ * strlen_user: - Get the size of a string in user space.
+ * @str: The string to measure.
+ * @n:   The maximum valid length
+ *
+ * Get the size of a NUL-terminated string in user space.
+ *
+ * Returns the size of the string INCLUDING the terminating NUL.
+ * On exception, returns 0.
+ * If the string is too long, returns a value greater than @n.
+ */
+long strnlen_user(const char *s, long n)
+{
+	unsigned long res, tmp;
+
+	if (s == NULL)
+		return 0;
+
+	asm volatile(
+	"       cmpnei  %1, 0           \n"
+	"       bf      3f              \n"
+	"1:     cmpnei  %0, 0           \n"
+	"       bf      3f              \n"
+	"2:     ldb     %3, (%1, 0)     \n"
+	"       cmpnei  %3, 0           \n"
+	"       bf      3f              \n"
+	"       subi    %0,  1          \n"
+	"       addi    %1,  1          \n"
+	"       br      1b              \n"
+	"3:     subu    %2, %0          \n"
+	"       addi    %2,  1          \n"
+	"       br      5f              \n"
+	"4:     movi    %0, 0           \n"
+	"       br      5f              \n"
+	".section __ex_table, \"a\"     \n"
+	".align   2                     \n"
+	".long    2b, 4b                \n"
+	".previous                      \n"
+	"5:                             \n"
+	: "=r"(n), "=r"(s), "=r"(res), "=r"(tmp)
+	: "0"(n), "1"(s), "2"(n)
+	: "memory", "cc");
+
+	return res;
+}
+EXPORT_SYMBOL(strnlen_user);
+
+#define __do_clear_user(addr, size)			\
+do {							\
+	int __d0, zvalue, tmp;				\
+							\
+	asm volatile(					\
+	"0:     cmpnei  %1, 0           \n"		\
+	"       bf      7f              \n"		\
+	"       mov     %3, %1          \n"		\
+	"       andi    %3, 3           \n"		\
+	"       cmpnei  %3, 0           \n"		\
+	"       bf      1f              \n"		\
+	"       br      5f              \n"		\
+	"1:     cmplti  %0, 32          \n" /* 4W */	\
+	"       bt      3f              \n"		\
+	"8:     stw     %2, (%1, 0)     \n"		\
+	"10:    stw     %2, (%1, 4)     \n"		\
+	"11:    stw     %2, (%1, 8)     \n"		\
+	"12:    stw     %2, (%1, 12)    \n"		\
+	"13:    stw     %2, (%1, 16)    \n"		\
+	"14:    stw     %2, (%1, 20)    \n"		\
+	"15:    stw     %2, (%1, 24)    \n"		\
+	"16:    stw     %2, (%1, 28)    \n"		\
+	"       addi    %1, 32          \n"		\
+	"       subi    %0, 32          \n"		\
+	"       br      1b              \n"		\
+	"3:     cmplti  %0, 4           \n" /* 1W */	\
+	"       bt      5f              \n"		\
+	"4:     stw     %2, (%1, 0)     \n"		\
+	"       addi    %1, 4           \n"		\
+	"       subi    %0, 4           \n"		\
+	"       br      3b              \n"		\
+	"5:     cmpnei  %0, 0           \n" /* 1B */	\
+	"9:     bf      7f              \n"		\
+	"6:     stb     %2, (%1, 0)     \n"		\
+	"       addi    %1,  1          \n"		\
+	"       subi    %0,  1          \n"		\
+	"       br      5b              \n"		\
+	".section __ex_table,\"a\"      \n"		\
+	".align   2                     \n"		\
+	".long    8b, 9b                \n"		\
+	".long    10b, 9b               \n"		\
+	".long    11b, 9b               \n"		\
+	".long    12b, 9b               \n"		\
+	".long    13b, 9b               \n"		\
+	".long    14b, 9b               \n"		\
+	".long    15b, 9b               \n"		\
+	".long    16b, 9b               \n"		\
+	".long    4b, 9b                \n"		\
+	".long    6b, 9b                \n"		\
+	".previous                      \n"		\
+	"7:                             \n"		\
+	: "=r"(size), "=r" (__d0),			\
+	  "=r"(zvalue), "=r"(tmp)			\
+	: "0"(size), "1"(addr), "2"(0)			\
+	: "memory", "cc");				\
+} while (0)
+
+/*
+ * clear_user: - Zero a block of memory in user space.
+ * @to:   Destination address, in user space.
+ * @n:    Number of bytes to zero.
+ *
+ * Zero a block of memory in user space.
+ *
+ * Returns number of bytes that could not be cleared.
+ * On success, this will be zero.
+ */
+unsigned long
+clear_user(void __user *to, unsigned long n)
+{
+	if (access_ok(VERIFY_WRITE, to, n))
+		__do_clear_user(to, n);
+	return n;
+}
+EXPORT_SYMBOL(clear_user);
+
+/*
+ * __clear_user: - Zero a block of memory in user space, with less checking.
+ * @to:   Destination address, in user space.
+ * @n:    Number of bytes to zero.
+ *
+ * Zero a block of memory in user space.  Caller must check
+ * the specified block with access_ok() before calling this function.
+ *
+ * Returns number of bytes that could not be cleared.
+ * On success, this will be zero.
+ */
+unsigned long
+__clear_user(void __user *to, unsigned long n)
+{
+	__do_clear_user(to, n);
+	return n;
+}
+EXPORT_SYMBOL(__clear_user);