a4bb1e43e2
kstrdup() is often used to duplicate strings where neither source neither
destination will be ever modified. In such case we can just reuse the
source instead of duplicating it. The problem is that we must be sure
that the source is non-modifiable and its life-time is long enough.
I suspect the good candidates for such strings are strings located in
kernel .rodata section, they cannot be modifed because the section is
read-only and their life-time is equal to kernel life-time.
This small patchset proposes alternative version of kstrdup -
kstrdup_const, which returns source string if it is located in .rodata
otherwise it fallbacks to kstrdup. To verify if the source is in
.rodata function checks if the address is between sentinels
__start_rodata, __end_rodata. I guess it should work with all
architectures.
The main patch is accompanied by four patches constifying kstrdup for
cases where situtation described above happens frequently.
I have tested the patchset on mobile platform (exynos4210-trats) and it
saves 3272 string allocations. Since minimal allocation is 32 or 64
bytes depending on Kconfig options the patchset saves respectively about
100KB or 200KB of memory.
Stats from tested platform show that the main offender is sysfs:
By caller:
2260 __kernfs_new_node
631 clk_register+0xc8/0x1b8
318 clk_register+0x34/0x1b8
51 kmem_cache_create
12 alloc_vfsmnt
By string (with count >= 5):
883 power
876 subsystem
135 parameters
132 device
61 iommu_group
...
This patch (of 5):
Add an alternative version of kstrdup which returns pointer to constant
char array. The function checks if input string is in persistent and
read-only memory section, if yes it returns the input string, otherwise it
fallbacks to kstrdup.
kstrdup_const is accompanied by kfree_const performing conditional memory
deallocation of the string.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
162 lines
4.5 KiB
C
162 lines
4.5 KiB
C
#ifndef _LINUX_STRING_H_
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#define _LINUX_STRING_H_
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#include <linux/compiler.h> /* for inline */
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#include <linux/types.h> /* for size_t */
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#include <linux/stddef.h> /* for NULL */
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#include <stdarg.h>
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#include <uapi/linux/string.h>
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extern char *strndup_user(const char __user *, long);
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extern void *memdup_user(const void __user *, size_t);
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/*
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* Include machine specific inline routines
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*/
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#include <asm/string.h>
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#ifndef __HAVE_ARCH_STRCPY
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extern char * strcpy(char *,const char *);
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#endif
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#ifndef __HAVE_ARCH_STRNCPY
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extern char * strncpy(char *,const char *, __kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_STRLCPY
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size_t strlcpy(char *, const char *, size_t);
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#endif
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#ifndef __HAVE_ARCH_STRCAT
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extern char * strcat(char *, const char *);
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#endif
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#ifndef __HAVE_ARCH_STRNCAT
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extern char * strncat(char *, const char *, __kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_STRLCAT
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extern size_t strlcat(char *, const char *, __kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_STRCMP
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extern int strcmp(const char *,const char *);
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#endif
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#ifndef __HAVE_ARCH_STRNCMP
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extern int strncmp(const char *,const char *,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_STRCASECMP
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extern int strcasecmp(const char *s1, const char *s2);
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#endif
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#ifndef __HAVE_ARCH_STRNCASECMP
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extern int strncasecmp(const char *s1, const char *s2, size_t n);
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#endif
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#ifndef __HAVE_ARCH_STRCHR
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extern char * strchr(const char *,int);
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#endif
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#ifndef __HAVE_ARCH_STRCHRNUL
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extern char * strchrnul(const char *,int);
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#endif
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#ifndef __HAVE_ARCH_STRNCHR
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extern char * strnchr(const char *, size_t, int);
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#endif
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#ifndef __HAVE_ARCH_STRRCHR
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extern char * strrchr(const char *,int);
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#endif
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extern char * __must_check skip_spaces(const char *);
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extern char *strim(char *);
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static inline __must_check char *strstrip(char *str)
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{
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return strim(str);
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}
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#ifndef __HAVE_ARCH_STRSTR
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extern char * strstr(const char *, const char *);
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#endif
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#ifndef __HAVE_ARCH_STRNSTR
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extern char * strnstr(const char *, const char *, size_t);
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#endif
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#ifndef __HAVE_ARCH_STRLEN
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extern __kernel_size_t strlen(const char *);
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#endif
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#ifndef __HAVE_ARCH_STRNLEN
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extern __kernel_size_t strnlen(const char *,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_STRPBRK
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extern char * strpbrk(const char *,const char *);
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#endif
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#ifndef __HAVE_ARCH_STRSEP
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extern char * strsep(char **,const char *);
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#endif
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#ifndef __HAVE_ARCH_STRSPN
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extern __kernel_size_t strspn(const char *,const char *);
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#endif
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#ifndef __HAVE_ARCH_STRCSPN
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extern __kernel_size_t strcspn(const char *,const char *);
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#endif
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#ifndef __HAVE_ARCH_MEMSET
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extern void * memset(void *,int,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_MEMCPY
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extern void * memcpy(void *,const void *,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_MEMMOVE
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extern void * memmove(void *,const void *,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_MEMSCAN
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extern void * memscan(void *,int,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_MEMCMP
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extern int memcmp(const void *,const void *,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_MEMCHR
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extern void * memchr(const void *,int,__kernel_size_t);
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#endif
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void *memchr_inv(const void *s, int c, size_t n);
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extern void kfree_const(const void *x);
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extern char *kstrdup(const char *s, gfp_t gfp);
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extern const char *kstrdup_const(const char *s, gfp_t gfp);
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extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
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extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
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extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
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extern void argv_free(char **argv);
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extern bool sysfs_streq(const char *s1, const char *s2);
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extern int strtobool(const char *s, bool *res);
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#ifdef CONFIG_BINARY_PRINTF
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int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);
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int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf);
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int bprintf(u32 *bin_buf, size_t size, const char *fmt, ...) __printf(3, 4);
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#endif
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extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
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const void *from, size_t available);
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/**
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* strstarts - does @str start with @prefix?
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* @str: string to examine
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* @prefix: prefix to look for.
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*/
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static inline bool strstarts(const char *str, const char *prefix)
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{
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return strncmp(str, prefix, strlen(prefix)) == 0;
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}
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size_t memweight(const void *ptr, size_t bytes);
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void memzero_explicit(void *s, size_t count);
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/**
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* kbasename - return the last part of a pathname.
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*
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* @path: path to extract the filename from.
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*/
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static inline const char *kbasename(const char *path)
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{
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const char *tail = strrchr(path, '/');
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return tail ? tail + 1 : path;
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}
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#endif /* _LINUX_STRING_H_ */
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