[PATCH v2 1/2] ARM: use generic strnlen_user and strncpy_from_user functions
From: Will Deacon
Date: Fri Jun 15 2012 - 12:22:39 EST
This patch implements the word-at-a-time interface for ARM using the
same algorithm as x86. We use the fls macro from ARMv5 onwards, where
we have a clz instruction available which saves us a mov instruction
when targetting Thumb-2. For older CPUs, we use the magic 0x0ff0001
constant. Big-endian configurations make use of the implementation from
asm-generic.
With this implemented, we can replace our byte-at-a-time strnlen_user
and strncpy_from_user functions with the optimised generic versions.
Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
---
arch/arm/Kconfig | 2 +
arch/arm/include/asm/uaccess.h | 27 +++------------
arch/arm/include/asm/word-at-a-time.h | 55 +++++++++++++++++++++++++++++++++
arch/arm/kernel/armksyms.c | 4 --
arch/arm/lib/Makefile | 1 -
arch/arm/lib/strncpy_from_user.S | 43 -------------------------
arch/arm/lib/strnlen_user.S | 40 ------------------------
7 files changed, 63 insertions(+), 109 deletions(-)
create mode 100644 arch/arm/include/asm/word-at-a-time.h
delete mode 100644 arch/arm/lib/strncpy_from_user.S
delete mode 100644 arch/arm/lib/strnlen_user.S
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 84449dd..77a2fad 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -45,6 +45,8 @@ config ARM
select GENERIC_SMP_IDLE_THREAD
select KTIME_SCALAR
select GENERIC_CLOCKEVENTS_BROADCAST if SMP
+ select GENERIC_STRNCPY_FROM_USER
+ select GENERIC_STRNLEN_USER
help
The ARM series is a line of low-power-consumption RISC chip designs
licensed by ARM Ltd and targeted at embedded applications and
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 71f6536..479a635 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -189,6 +189,9 @@ static inline void set_fs(mm_segment_t fs)
#define access_ok(type,addr,size) (__range_ok(addr,size) == 0)
+#define user_addr_max() \
+ (segment_eq(get_fs(), USER_DS) ? TASK_SIZE : ~0UL)
+
/*
* The "__xxx" versions of the user access functions do not verify the
* address space - it must have been done previously with a separate
@@ -398,9 +401,6 @@ extern unsigned long __must_check __clear_user_std(void __user *addr, unsigned l
#define __clear_user(addr,n) (memset((void __force *)addr, 0, n), 0)
#endif
-extern unsigned long __must_check __strncpy_from_user(char *to, const char __user *from, unsigned long count);
-extern unsigned long __must_check __strnlen_user(const char __user *s, long n);
-
static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
{
if (access_ok(VERIFY_READ, from, n))
@@ -427,24 +427,9 @@ static inline unsigned long __must_check clear_user(void __user *to, unsigned lo
return n;
}
-static inline long __must_check strncpy_from_user(char *dst, const char __user *src, long count)
-{
- long res = -EFAULT;
- if (access_ok(VERIFY_READ, src, 1))
- res = __strncpy_from_user(dst, src, count);
- return res;
-}
-
-#define strlen_user(s) strnlen_user(s, ~0UL >> 1)
+extern long strncpy_from_user(char *dest, const char __user *src, long count);
-static inline long __must_check strnlen_user(const char __user *s, long n)
-{
- unsigned long res = 0;
-
- if (__addr_ok(s))
- res = __strnlen_user(s, n);
-
- return res;
-}
+extern __must_check long strlen_user(const char __user *str);
+extern __must_check long strnlen_user(const char __user *str, long n);
#endif /* _ASMARM_UACCESS_H */
diff --git a/arch/arm/include/asm/word-at-a-time.h b/arch/arm/include/asm/word-at-a-time.h
new file mode 100644
index 0000000..74b2d45
--- /dev/null
+++ b/arch/arm/include/asm/word-at-a-time.h
@@ -0,0 +1,55 @@
+#ifndef __ASM_ARM_WORD_AT_A_TIME_H
+#define __ASM_ARM_WORD_AT_A_TIME_H
+
+#ifndef __ARMEB__
+
+/*
+ * Little-endian word-at-a-time zero byte handling.
+ * Heavily based on the x86 algorithm.
+ */
+#include <linux/kernel.h>
+
+struct word_at_a_time {
+ const unsigned long one_bits, high_bits;
+};
+
+#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
+
+static inline unsigned long has_zero(unsigned long a, unsigned long *bits,
+ const struct word_at_a_time *c)
+{
+ unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
+ *bits = mask;
+ return mask;
+}
+
+#define prep_zero_mask(a, bits, c) (bits)
+
+static inline unsigned long create_zero_mask(unsigned long bits)
+{
+ bits = (bits - 1) & ~bits;
+ return bits >> 7;
+}
+
+static inline unsigned long find_zero(unsigned long mask)
+{
+ unsigned long ret;
+
+#if __LINUX_ARM_ARCH__ >= 5
+ /* We have clz available. */
+ ret = fls(mask) >> 3;
+#else
+ /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
+ ret = (0x0ff0001 + mask) >> 23;
+ /* Fix the 1 for 00 case */
+ ret &= mask;
+#endif
+
+ return ret;
+}
+
+#else /* __ARMEB__ */
+#include <asm-generic/word-at-a-time.h>
+#endif
+
+#endif /* __ASM_ARM_WORD_AT_A_TIME_H */
diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index b57c75e..c3dff6a 100644
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -87,10 +87,6 @@ EXPORT_SYMBOL(memmove);
EXPORT_SYMBOL(memchr);
EXPORT_SYMBOL(__memzero);
- /* user mem (segment) */
-EXPORT_SYMBOL(__strnlen_user);
-EXPORT_SYMBOL(__strncpy_from_user);
-
#ifdef CONFIG_MMU
EXPORT_SYMBOL(copy_page);
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 992769a..d5060da 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -8,7 +8,6 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
delay.o findbit.o memchr.o memcpy.o \
memmove.o memset.o memzero.o setbit.o \
- strncpy_from_user.o strnlen_user.o \
strchr.o strrchr.o \
testchangebit.o testclearbit.o testsetbit.o \
ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \
diff --git a/arch/arm/lib/strncpy_from_user.S b/arch/arm/lib/strncpy_from_user.S
deleted file mode 100644
index f202d7b..0000000
--- a/arch/arm/lib/strncpy_from_user.S
+++ /dev/null
@@ -1,43 +0,0 @@
-/*
- * linux/arch/arm/lib/strncpy_from_user.S
- *
- * Copyright (C) 1995-2000 Russell King
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-#include <linux/linkage.h>
-#include <asm/assembler.h>
-#include <asm/errno.h>
-
- .text
- .align 5
-
-/*
- * Copy a string from user space to kernel space.
- * r0 = dst, r1 = src, r2 = byte length
- * returns the number of characters copied (strlen of copied string),
- * -EFAULT on exception, or "len" if we fill the whole buffer
- */
-ENTRY(__strncpy_from_user)
- mov ip, r1
-1: subs r2, r2, #1
- ldrusr r3, r1, 1, pl
- bmi 2f
- strb r3, [r0], #1
- teq r3, #0
- bne 1b
- sub r1, r1, #1 @ take NUL character out of count
-2: sub r0, r1, ip
- mov pc, lr
-ENDPROC(__strncpy_from_user)
-
- .pushsection .fixup,"ax"
- .align 0
-9001: mov r3, #0
- strb r3, [r0, #0] @ null terminate
- mov r0, #-EFAULT
- mov pc, lr
- .popsection
-
diff --git a/arch/arm/lib/strnlen_user.S b/arch/arm/lib/strnlen_user.S
deleted file mode 100644
index 0ecbb45..0000000
--- a/arch/arm/lib/strnlen_user.S
+++ /dev/null
@@ -1,40 +0,0 @@
-/*
- * linux/arch/arm/lib/strnlen_user.S
- *
- * Copyright (C) 1995-2000 Russell King
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-#include <linux/linkage.h>
-#include <asm/assembler.h>
-#include <asm/errno.h>
-
- .text
- .align 5
-
-/* Prototype: unsigned long __strnlen_user(const char *str, long n)
- * Purpose : get length of a string in user memory
- * Params : str - address of string in user memory
- * Returns : length of string *including terminator*
- * or zero on exception, or n + 1 if too long
- */
-ENTRY(__strnlen_user)
- mov r2, r0
-1:
- ldrusr r3, r0, 1
- teq r3, #0
- beq 2f
- subs r1, r1, #1
- bne 1b
- add r0, r0, #1
-2: sub r0, r0, r2
- mov pc, lr
-ENDPROC(__strnlen_user)
-
- .pushsection .fixup,"ax"
- .align 0
-9001: mov r0, #0
- mov pc, lr
- .popsection
--
1.7.4.1
--
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