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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
parent9978306e31a8f89bd81fbc4c49fd9aefb1d30d10 (diff)
parentc5389831cda3b38a56606a348a537a1332f2d729 (diff)
downloadlinux-ce004178be1bbaa292e9e6497939e2970300095a.tar.gz
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()
-rw-r--r--arch/sparc/Kconfig2
-rw-r--r--arch/sparc/include/asm/processor_64.h4
-rw-r--r--arch/sparc/include/asm/thread_info_32.h11
-rw-r--r--arch/sparc/include/asm/uaccess.h6
-rw-r--r--arch/sparc/include/asm/uaccess_32.h10
-rw-r--r--arch/sparc/include/asm/uaccess_64.h4
-rw-r--r--arch/sparc/lib/Makefile2
-rw-r--r--arch/sparc/lib/ksyms.c3
-rw-r--r--arch/sparc/lib/strncpy_from_user_32.S47
-rw-r--r--arch/sparc/lib/strncpy_from_user_64.S133
-rw-r--r--arch/sparc/lib/usercopy.c1
-rw-r--r--arch/sparc/mm/srmmu.c27
-rw-r--r--arch/x86/include/asm/word-at-a-time.h4
-rw-r--r--fs/namei.c1
-rw-r--r--include/linux/kernel.h2
-rw-r--r--lib/Kconfig3
-rw-r--r--lib/Makefile2
-rw-r--r--lib/strncpy_from_user.c146
18 files changed, 170 insertions, 238 deletions
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 2d493a3bdfe..15e9e05740d 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -34,12 +34,12 @@ config SPARC
select GENERIC_SMP_IDLE_THREAD
select GENERIC_CMOS_UPDATE
select GENERIC_CLOCKEVENTS
+ select GENERIC_STRNCPY_FROM_USER
config SPARC32
def_bool !64BIT
select GENERIC_ATOMIC64
select CLZ_TAB
- select ARCH_THREAD_INFO_ALLOCATOR
select ARCH_USES_GETTIMEOFFSET
config SPARC64
diff --git a/arch/sparc/include/asm/processor_64.h b/arch/sparc/include/asm/processor_64.h
index 67df5cc1001..4e5a483122a 100644
--- a/arch/sparc/include/asm/processor_64.h
+++ b/arch/sparc/include/asm/processor_64.h
@@ -42,7 +42,9 @@
#define TASK_SIZE_OF(tsk) \
(test_tsk_thread_flag(tsk,TIF_32BIT) ? \
(1UL << 32UL) : ((unsigned long)-VPTE_SIZE))
-#define TASK_SIZE TASK_SIZE_OF(current)
+#define TASK_SIZE \
+ (test_thread_flag(TIF_32BIT) ? \
+ (1UL << 32UL) : ((unsigned long)-VPTE_SIZE))
#ifdef __KERNEL__
#define STACK_TOP32 ((1UL << 32UL) - PAGE_SIZE)
diff --git a/arch/sparc/include/asm/thread_info_32.h b/arch/sparc/include/asm/thread_info_32.h
index 21a38946541..5af66493245 100644
--- a/arch/sparc/include/asm/thread_info_32.h
+++ b/arch/sparc/include/asm/thread_info_32.h
@@ -77,18 +77,11 @@ register struct thread_info *current_thread_info_reg asm("g6");
/*
* thread information allocation
*/
-#define THREAD_INFO_ORDER 1
-
-struct thread_info * alloc_thread_info_node(struct task_struct *tsk, int node);
-void free_thread_info(struct thread_info *);
+#define THREAD_SIZE_ORDER 1
#endif /* __ASSEMBLY__ */
-/*
- * Size of kernel stack for each process.
- * Observe the order of get_free_pages() in alloc_thread_info_node().
- * The sun4 has 8K stack too, because it's short on memory, and 16K is a waste.
- */
+/* Size of kernel stack for each process */
#define THREAD_SIZE (2 * PAGE_SIZE)
/*
diff --git a/arch/sparc/include/asm/uaccess.h b/arch/sparc/include/asm/uaccess.h
index e88fbe5c045..0167d26d0d1 100644
--- a/arch/sparc/include/asm/uaccess.h
+++ b/arch/sparc/include/asm/uaccess.h
@@ -5,4 +5,10 @@
#else
#include <asm/uaccess_32.h>
#endif
+
+#define user_addr_max() \
+ (segment_eq(get_fs(), USER_DS) ? TASK_SIZE : ~0UL)
+
+extern long strncpy_from_user(char *dest, const char __user *src, long count);
+
#endif
diff --git a/arch/sparc/include/asm/uaccess_32.h b/arch/sparc/include/asm/uaccess_32.h
index d50c310f5d3..59586b57ef1 100644
--- a/arch/sparc/include/asm/uaccess_32.h
+++ b/arch/sparc/include/asm/uaccess_32.h
@@ -304,16 +304,6 @@ static inline unsigned long clear_user(void __user *addr, unsigned long n)
return n;
}
-extern long __strncpy_from_user(char *dest, const char __user *src, long count);
-
-static inline long strncpy_from_user(char *dest, const char __user *src, long count)
-{
- if (__access_ok((unsigned long) src, count))
- return __strncpy_from_user(dest, src, count);
- else
- return -EFAULT;
-}
-
extern long __strlen_user(const char __user *);
extern long __strnlen_user(const char __user *, long len);
diff --git a/arch/sparc/include/asm/uaccess_64.h b/arch/sparc/include/asm/uaccess_64.h
index a1091afb883..dcdfb89cbf3 100644
--- a/arch/sparc/include/asm/uaccess_64.h
+++ b/arch/sparc/include/asm/uaccess_64.h
@@ -257,10 +257,6 @@ extern unsigned long __must_check __clear_user(void __user *, unsigned long);
#define clear_user __clear_user
-extern long __must_check __strncpy_from_user(char *dest, const char __user *src, long count);
-
-#define strncpy_from_user __strncpy_from_user
-
extern long __strlen_user(const char __user *);
extern long __strnlen_user(const char __user *, long len);
diff --git a/arch/sparc/lib/Makefile b/arch/sparc/lib/Makefile
index 389628f50a1..943d98dc4cd 100644
--- a/arch/sparc/lib/Makefile
+++ b/arch/sparc/lib/Makefile
@@ -10,7 +10,7 @@ lib-y += strlen.o
lib-y += checksum_$(BITS).o
lib-$(CONFIG_SPARC32) += blockops.o
lib-y += memscan_$(BITS).o memcmp.o strncmp_$(BITS).o
-lib-y += strncpy_from_user_$(BITS).o strlen_user_$(BITS).o
+lib-y += strlen_user_$(BITS).o
lib-$(CONFIG_SPARC32) += divdi3.o udivdi3.o
lib-$(CONFIG_SPARC32) += copy_user.o locks.o
lib-$(CONFIG_SPARC64) += atomic_64.o
diff --git a/arch/sparc/lib/ksyms.c b/arch/sparc/lib/ksyms.c
index 2dc30875c8b..6b278abdb63 100644
--- a/arch/sparc/lib/ksyms.c
+++ b/arch/sparc/lib/ksyms.c
@@ -33,9 +33,6 @@ EXPORT_SYMBOL(memset);
EXPORT_SYMBOL(memmove);
EXPORT_SYMBOL(__bzero);
-/* Moving data to/from/in userspace. */
-EXPORT_SYMBOL(__strncpy_from_user);
-
/* Networking helper routines. */
EXPORT_SYMBOL(csum_partial);
diff --git a/arch/sparc/lib/strncpy_from_user_32.S b/arch/sparc/lib/strncpy_from_user_32.S
deleted file mode 100644
index db0ed2964bd..00000000000
--- a/arch/sparc/lib/strncpy_from_user_32.S
+++ /dev/null
@@ -1,47 +0,0 @@
-/* strncpy_from_user.S: Sparc strncpy from userspace.
- *
- * Copyright(C) 1996 David S. Miller
- */
-
-#include <linux/linkage.h>
-#include <asm/ptrace.h>
-#include <asm/errno.h>
-
- .text
-
- /* Must return:
- *
- * -EFAULT for an exception
- * count if we hit the buffer limit
- * bytes copied if we hit a null byte
- */
-
-ENTRY(__strncpy_from_user)
- /* %o0=dest, %o1=src, %o2=count */
- mov %o2, %o3
-1:
- subcc %o2, 1, %o2
- bneg 2f
- nop
-10:
- ldub [%o1], %o4
- add %o0, 1, %o0
- cmp %o4, 0
- add %o1, 1, %o1
- bne 1b
- stb %o4, [%o0 - 1]
-2:
- add %o2, 1, %o0
- retl
- sub %o3, %o0, %o0
-ENDPROC(__strncpy_from_user)
-
- .section .fixup,#alloc,#execinstr
- .align 4
-4:
- retl
- mov -EFAULT, %o0
-
- .section __ex_table,#alloc
- .align 4
- .word 10b, 4b
diff --git a/arch/sparc/lib/strncpy_from_user_64.S b/arch/sparc/lib/strncpy_from_user_64.S
deleted file mode 100644
index d1246b71307..00000000000
--- a/arch/sparc/lib/strncpy_from_user_64.S
+++ /dev/null
@@ -1,133 +0,0 @@
-/*
- * strncpy_from_user.S: Sparc64 strncpy from userspace.
- *
- * Copyright (C) 1997, 1999 Jakub Jelinek (jj@ultra.linux.cz)
- */
-
-#include <linux/linkage.h>
-#include <asm/asi.h>
-#include <asm/errno.h>
-
- .data
- .align 8
-0: .xword 0x0101010101010101
-
- .text
-
- /* 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)
- *
- * This implementation assumes:
- * %o1 is 8 aligned => !(%o2 & 7)
- * %o0 is 8 aligned (if not, it will be slooooow, but will work)
- *
- * This is optimized for the common case:
- * in my stats, 90% of src are 8 aligned (even on sparc32)
- * and average length is 18 or so.
- */
-
-ENTRY(__strncpy_from_user)
- /* %o0=dest, %o1=src, %o2=count */
- andcc %o1, 7, %g0 ! IEU1 Group
- bne,pn %icc, 30f ! CTI
- add %o0, %o2, %g3 ! IEU0
-60: ldxa [%o1] %asi, %g1 ! Load Group
- brlez,pn %o2, 10f ! CTI
- mov %o0, %o3 ! IEU0
-50: sethi %hi(0b), %o4 ! IEU0 Group
- ldx [%o4 + %lo(0b)], %o4 ! Load
- sllx %o4, 7, %o5 ! IEU1 Group
-1: sub %g1, %o4, %g2 ! IEU0 Group
- stx %g1, [%o0] ! Store
- add %o0, 8, %o0 ! IEU1
- andcc %g2, %o5, %g0 ! IEU1 Group
- bne,pn %xcc, 5f ! CTI
- add %o1, 8, %o1 ! IEU0
- cmp %o0, %g3 ! IEU1 Group
- bl,a,pt %xcc, 1b ! CTI
-61: ldxa [%o1] %asi, %g1 ! Load
-10: retl ! CTI Group
- mov %o2, %o0 ! IEU0
-5: srlx %g2, 32, %g7 ! IEU0 Group
- sethi %hi(0xff00), %o4 ! IEU1
- andcc %g7, %o5, %g0 ! IEU1 Group
- be,pn %icc, 2f ! CTI
- or %o4, %lo(0xff00), %o4 ! IEU0
- srlx %g1, 48, %g7 ! IEU0 Group
- andcc %g7, %o4, %g0 ! IEU1 Group
- be,pn %icc, 50f ! CTI
- andcc %g7, 0xff, %g0 ! IEU1 Group
- be,pn %icc, 51f ! CTI
- srlx %g1, 32, %g7 ! IEU0
- andcc %g7, %o4, %g0 ! IEU1 Group
- be,pn %icc, 52f ! CTI
- andcc %g7, 0xff, %g0 ! IEU1 Group
- be,pn %icc, 53f ! CTI
-2: andcc %g2, %o5, %g0 ! IEU1 Group
- be,pn %icc, 2f ! CTI
- srl %g1, 16, %g7 ! IEU0
- andcc %g7, %o4, %g0 ! IEU1 Group
- be,pn %icc, 54f ! CTI
- andcc %g7, 0xff, %g0 ! IEU1 Group
- be,pn %icc, 55f ! CTI
- andcc %g1, %o4, %g0 ! IEU1 Group
- be,pn %icc, 56f ! CTI
- andcc %g1, 0xff, %g0 ! IEU1 Group
- be,a,pn %icc, 57f ! CTI
- sub %o0, %o3, %o0 ! IEU0
-2: cmp %o0, %g3 ! IEU1 Group
- bl,a,pt %xcc, 50b ! CTI
-62: ldxa [%o1] %asi, %g1 ! Load
- retl ! CTI Group
- mov %o2, %o0 ! IEU0
-50: sub %o0, %o3, %o0
- retl
- sub %o0, 8, %o0
-51: sub %o0, %o3, %o0
- retl
- sub %o0, 7, %o0
-52: sub %o0, %o3, %o0
- retl
- sub %o0, 6, %o0
-53: sub %o0, %o3, %o0
- retl
- sub %o0, 5, %o0
-54: sub %o0, %o3, %o0
- retl
- sub %o0, 4, %o0
-55: sub %o0, %o3, %o0
- retl
- sub %o0, 3, %o0
-56: sub %o0, %o3, %o0
- retl
- sub %o0, 2, %o0
-57: retl
- sub %o0, 1, %o0
-30: brlez,pn %o2, 3f
- sub %g0, %o2, %o3
- add %o0, %o2, %o0
-63: lduba [%o1] %asi, %o4
-1: add %o1, 1, %o1
- brz,pn %o4, 2f
- stb %o4, [%o0 + %o3]
- addcc %o3, 1, %o3
- bne,pt %xcc, 1b
-64: lduba [%o1] %asi, %o4
-3: retl
- mov %o2, %o0
-2: retl
- add %o2, %o3, %o0
-ENDPROC(__strncpy_from_user)
-
- .section __ex_table,"a"
- .align 4
- .word 60b, __retl_efault
- .word 61b, __retl_efault
- .word 62b, __retl_efault
- .word 63b, __retl_efault
- .word 64b, __retl_efault
- .previous
diff --git a/arch/sparc/lib/usercopy.c b/arch/sparc/lib/usercopy.c
index 14b363fec8a..5c4284ce1c0 100644
--- a/arch/sparc/lib/usercopy.c
+++ b/arch/sparc/lib/usercopy.c
@@ -1,4 +1,5 @@
#include <linux/module.h>
+#include <linux/kernel.h>
#include <linux/bug.h>
void copy_from_user_overflow(void)
diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index 8e97e0305b0..256db6b22c5 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -467,33 +467,6 @@ void srmmu_unmapiorange(unsigned long virt_addr, unsigned int len)
flush_tlb_all();
}
-/*
- * On the SRMMU we do not have the problems with limited tlb entries
- * for mapping kernel pages, so we just take things from the free page
- * pool. As a side effect we are putting a little too much pressure
- * on the gfp() subsystem. This setup also makes the logic of the
- * iommu mapping code a lot easier as we can transparently handle
- * mappings on the kernel stack without any special code.
- */
-struct thread_info *alloc_thread_info_node(struct task_struct *tsk, int node)
-{
- struct thread_info *ret;
-
- ret = (struct thread_info *)__get_free_pages(GFP_KERNEL,
- THREAD_INFO_ORDER);
-#ifdef CONFIG_DEBUG_STACK_USAGE
- if (ret)
- memset(ret, 0, PAGE_SIZE << THREAD_INFO_ORDER);
-#endif /* DEBUG_STACK_USAGE */
-
- return ret;
-}
-
-void free_thread_info(struct thread_info *ti)
-{
- free_pages((unsigned long)ti, THREAD_INFO_ORDER);
-}
-
/* tsunami.S */
extern void tsunami_flush_cache_all(void);
extern void tsunami_flush_cache_mm(struct mm_struct *mm);
diff --git a/arch/x86/include/asm/word-at-a-time.h b/arch/x86/include/asm/word-at-a-time.h
index e58f03b206c..ae03facfadd 100644
--- a/arch/x86/include/asm/word-at-a-time.h
+++ b/arch/x86/include/asm/word-at-a-time.h
@@ -1,6 +1,8 @@
#ifndef _ASM_WORD_AT_A_TIME_H
#define _ASM_WORD_AT_A_TIME_H
+#include <linux/kernel.h>
+
/*
* This is largely generic for little-endian machines, but the
* optimal byte mask counting is probably going to be something
@@ -35,8 +37,6 @@ static inline long count_masked_bytes(long mask)
#endif
-#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
-
/* Return the high bit set in the first byte that is a zero */
static inline unsigned long has_zero(unsigned long a)
{
diff --git a/fs/namei.c b/fs/namei.c
index e70ebab9624..93ff12b1a1d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -16,6 +16,7 @@
#include <linux/init.h>
#include <linux/export.h>
+#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/namei.h>
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index c0d34420a91..ec55a3c8ba7 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -38,6 +38,8 @@
#define STACK_MAGIC 0xdeadbeef
+#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
+
#define ALIGN(x, a) __ALIGN_KERNEL((x), (a))
#define __ALIGN_MASK(x, mask) __ALIGN_KERNEL_MASK((x), (mask))
#define PTR_ALIGN(p, a) ((typeof(p))ALIGN((unsigned long)(p), (a)))
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);