On Mon, Jan 12, 2015 at 10:18 AM, Andrzej Hajda <a.ha...@samsung.com> wrote: > kstrdup if 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.
It also introduces kfree_const(const void *x). As kfree_const() has the exact same signature as kfree(), the risk of accidentally passing pointers returned from kstrdup_const() to kfree() seems high, which may lead to memory corruption if the pointer doesn't point to allocated memory. > 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. > > As I have tested the patchset on mobile platform (exynos4210-trats) 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. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/