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authorLinus Torvalds <torvalds@linux-foundation.org>2012-05-24 15:10:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-24 15:10:28 -0700
commitce004178be1bbaa292e9e6497939e2970300095a (patch)
tree1cd5306548947deaedd612189b56d35265217e8e /lib
parent9978306e31a8f89bd81fbc4c49fd9aefb1d30d10 (diff)
parentc5389831cda3b38a56606a348a537a1332f2d729 (diff)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc
Pull sparc changes from David S. Miller: "This has the generic strncpy_from_user() implementation architectures can now use, which we've been developing on linux-arch over the past few days. For good measure I ran both a 32-bit and a 64-bit glibc testsuite run, and the latter of which pointed out an adjustment I needed to make to sparc's user_addr_max() definition. Linus, you were right, STACK_TOP was not the right thing to use, even on sparc itself :-) From Sam Ravnborg, we have a conversion of sparc32 over to the common alloc_thread_info_node(), since the aspect which originally blocked our doing so (sun4c) has been removed." Fix up trivial arch/sparc/Kconfig and lib/Makefile conflicts. * git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc: sparc: Fix user_addr_max() definition. lib: Sparc's strncpy_from_user is generic enough, move under lib/ kernel: Move REPEAT_BYTE definition into linux/kernel.h sparc: Increase portability of strncpy_from_user() implementation. sparc: Optimize strncpy_from_user() zero byte search. sparc: Add full proper error handling to strncpy_from_user(). sparc32: use the common implementation of alloc_thread_info_node()
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig3
-rw-r--r--lib/Makefile2
-rw-r--r--lib/strncpy_from_user.c146
3 files changed, 151 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index 0e25c03939e..98230ac3db2 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -16,6 +16,9 @@ config BITREVERSE
config RATIONAL
boolean
+config GENERIC_STRNCPY_FROM_USER
+ bool
+
config GENERIC_FIND_FIRST_BIT
bool
diff --git a/lib/Makefile b/lib/Makefile
index 74290c9e286..b98df505f33 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -125,6 +125,8 @@ obj-$(CONFIG_CLZ_TAB) += clz_tab.o
obj-$(CONFIG_DDR) += jedec_ddr_data.o
+obj-$(CONFIG_GENERIC_STRNCPY_FROM_USER) += strncpy_from_user.o
+
hostprogs-y := gen_crc32table
clean-files := crc32table.h
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
new file mode 100644
index 00000000000..c4c09b0e96b
--- /dev/null
+++ b/lib/strncpy_from_user.c
@@ -0,0 +1,146 @@
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+
+#include <asm/byteorder.h>
+
+static inline long find_zero(unsigned long mask)
+{
+ long byte = 0;
+
+#ifdef __BIG_ENDIAN
+#ifdef CONFIG_64BIT
+ if (mask >> 32)
+ mask >>= 32;
+ else
+ byte = 4;
+#endif
+ if (mask >> 16)
+ mask >>= 16;
+ else
+ byte += 2;
+ return (mask >> 8) ? byte : byte + 1;
+#else
+#ifdef CONFIG_64BIT
+ if (!((unsigned int) mask)) {
+ mask >>= 32;
+ byte = 4;
+ }
+#endif
+ if (!(mask & 0xffff)) {
+ mask >>= 16;
+ byte += 2;
+ }
+ return (mask & 0xff) ? byte : byte + 1;
+#endif
+}
+
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+#define IS_UNALIGNED(src, dst) 0
+#else
+#define IS_UNALIGNED(src, dst) \
+ (((long) dst | (long) src) & (sizeof(long) - 1))
+#endif
+
+/*
+ * Do a strncpy, return length of string without final '\0'.
+ * 'count' is the user-supplied count (return 'count' if we
+ * hit it), 'max' is the address space maximum (and we return
+ * -EFAULT if we hit it).
+ */
+static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max)
+{
+ const unsigned long high_bits = REPEAT_BYTE(0xfe) + 1;
+ const unsigned long low_bits = REPEAT_BYTE(0x7f);
+ long res = 0;
+
+ /*
+ * Truncate 'max' to the user-specified limit, so that
+ * we only have one limit we need to check in the loop
+ */
+ if (max > count)
+ max = count;
+
+ if (IS_UNALIGNED(src, dst))
+ goto byte_at_a_time;
+
+ while (max >= sizeof(unsigned long)) {
+ unsigned long c, v, rhs;
+
+ /* Fall back to byte-at-a-time if we get a page fault */
+ if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
+ break;
+ rhs = c | low_bits;
+ v = (c + high_bits) & ~rhs;
+ *(unsigned long *)(dst+res) = c;
+ if (v) {
+ v = (c & low_bits) + low_bits;
+ v = ~(v | rhs);
+ return res + find_zero(v);
+ }
+ res += sizeof(unsigned long);
+ max -= sizeof(unsigned long);
+ }
+
+byte_at_a_time:
+ while (max) {
+ char c;
+
+ if (unlikely(__get_user(c,src+res)))
+ return -EFAULT;
+ dst[res] = c;
+ if (!c)
+ return res;
+ res++;
+ max--;
+ }
+
+ /*
+ * Uhhuh. We hit 'max'. But was that the user-specified maximum
+ * too? If so, that's ok - we got as much as the user asked for.
+ */
+ if (res >= count)
+ return res;
+
+ /*
+ * Nope: we hit the address space limit, and we still had more
+ * characters the caller would have wanted. That's an EFAULT.
+ */
+ return -EFAULT;
+}
+
+/**
+ * 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 __user *src, long count)
+{
+ unsigned long max_addr, src_addr;
+
+ if (unlikely(count <= 0))
+ return 0;
+
+ max_addr = user_addr_max();
+ src_addr = (unsigned long)src;
+ if (likely(src_addr < max_addr)) {
+ unsigned long max = max_addr - src_addr;
+ return do_strncpy_from_user(dst, src, count, max);
+ }
+ return -EFAULT;
+}
+EXPORT_SYMBOL(strncpy_from_user);