x86: use generic strncpy_from_user routine
The generic strncpy_from_user() is not really optimal, since it is
designed to work on both little-endian and big-endian. And on
little-endian you can simplify much of the logic to find the first zero
byte, since little-endian arithmetic doesn't have to worry about the
carry bit propagating into earlier bytes (only later bytes, which we
don't care about).
But I have patches to make the generic routines use the architecture-
specific <asm/word-at-a-time.h> infrastructure, so that we can regain
the little-endian optimizations. But before we do that, switch over to
the generic routines to make the patches each do just one well-defined
thing.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 81c3e8b..3220d44 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -93,6 +93,7 @@
select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)
select GENERIC_TIME_VSYSCALL if X86_64
select KTIME_SCALAR if X86_32
+ select GENERIC_STRNCPY_FROM_USER
config INSTRUCTION_DECODER
def_bool (KPROBES || PERF_EVENTS || UPROBES)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 851fe0d..1354fac 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -32,6 +32,7 @@
#define segment_eq(a, b) ((a).seg == (b).seg)
+#define user_addr_max() (current_thread_info()->addr_limit.seg)
#define __addr_ok(addr) \
((unsigned long __force)(addr) < \
(current_thread_info()->addr_limit.seg))
diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index 2e4e4b0..f61ee67 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -43,100 +43,3 @@
return len;
}
EXPORT_SYMBOL_GPL(copy_from_user_nmi);
-
-/*
- * 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)
-{
- 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;
-
- while (max >= sizeof(unsigned long)) {
- unsigned long c, mask;
-
- /* Fall back to byte-at-a-time if we get a page fault */
- if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
- break;
- mask = has_zero(c);
- if (mask) {
- mask = (mask - 1) & ~mask;
- mask >>= 7;
- *(unsigned long *)(dst+res) = c & mask;
- return res + count_masked_bytes(mask);
- }
- *(unsigned long *)(dst+res) = c;
- res += sizeof(unsigned long);
- max -= sizeof(unsigned long);
- }
-
- 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 = current_thread_info()->addr_limit.seg;
- 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);