[patch 1/2] kstrdup: implementation

[patch 1/2] kstrdup: implementation

[Robert Love]

Rusty and I's LCA kernel tutorial again brought up kstrdup().  Let's
close this never ending saga and provide a standard kernel
implementation.

As an example of the savings from such a patch, there are a handful of
existing strdup() implementations and what looks like 100s of open coded
strdup() uses.  Some of which are surely buggy or less optimal than our
version, and all of which bloat the kernel.

Andrew, patch is against 2.6.12-rc3.

Best,

	Robert Love


The world continually reimplements kstrdup().  Implement an optimal version
and export it to the world.

By: Robert Love and Rusty Russell.

Signed-off-by: Robert Love <rml@novell.com>

 include/linux/string.h |    1 +
 lib/string.c           |   20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff -urN linux-2.6.12-rc3/include/linux/string.h linux/include/linux/string.h
--- linux-2.6.12-rc3/include/linux/string.h	2005-03-02 02:38:07.000000000 -0500
+++ linux/include/linux/string.h	2005-04-21 21:23:04.000000000 -0400
@@ -17,6 +17,7 @@
 extern char * strsep(char **,const char *);
 extern __kernel_size_t strspn(const char *,const char *);
 extern __kernel_size_t strcspn(const char *,const char *);
+extern char * kstrdup(const char *,unsigned int __nocast);
 
 /*
  * Include machine specific inline routines
diff -urN linux-2.6.12-rc3/lib/string.c linux/lib/string.c
--- linux-2.6.12-rc3/lib/string.c	2005-03-02 02:38:25.000000000 -0500
+++ linux/lib/string.c	2005-04-21 21:31:11.000000000 -0400
@@ -22,6 +22,7 @@
 #include <linux/types.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
+#include <linux/slab.h>
 #include <linux/module.h>
 
 #ifndef __HAVE_ARCH_STRNICMP
@@ -76,6 +77,25 @@
 EXPORT_SYMBOL(strcpy);
 #endif
 
+/*
+ * kstrdup - allocate space for and then copy an existing string
+ *
+ * @str: the string to duplicate
+ * @gfp: the GFP mask used to allocate the storage for the duplicated string
+ */
+char * kstrdup(const char *str, unsigned int __nocast flags)
+{
+	size_t len;
+	char *buf;
+
+	len = strlen(str) + 1;
+	buf = kmalloc(len, flags);
+	if (likely(buf))
+		memcpy(buf, str, len);
+	return buf;
+}
+EXPORT_SYMBOL(kstrdup);
+
 #ifndef __HAVE_ARCH_STRNCPY
 /**
  * strncpy - Copy a length-limited, %NUL-terminated string

Re: [patch 1/2] kstrdup: implementation

[Adrian Bunk]

On Thu, Apr 21, 2005 at 11:41:15PM -0400, Robert Love wrote:

> Rusty and I's LCA kernel tutorial again brought up kstrdup().  Let's
> close this never ending saga and provide a standard kernel
> implementation.
>...
 
This is a good example why development against Linus' tree is ofter 
pointless:

A similar patch is already in -mm.

> Best,
> 
> 	Robert Love
>...

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

Re: [patch 1/2] kstrdup: implementation

[Robert Love]

On Fri, 2005-04-22 at 05:51 +0200, Adrian Bunk wrote:

> This is a good example why development against Linus' tree is ofter 
> pointless:

Seriously.

> A similar patch is already in -mm.

But...woohoo!

	Robert Love