user/sven/linux.git/include/linux/string.h, branch v3.16.74

lib/string.c: implement a basic bcmp

2019-08-13T11:39:03Z

commit 5f074f3e192f10c9fade898b9b3b8812e3d83342 upstream. A recent optimization in Clang (r355672) lowers comparisons of the return value of memcmp against zero to comparisons of the return value of bcmp against zero. This helps some platforms that implement bcmp more efficiently than memcmp. glibc simply aliases bcmp to memcmp, but an optimized implementation is in the works. This results in linkage failures for all targets with Clang due to the undefined symbol. For now, just implement bcmp as a tailcail to memcmp to unbreak the build. This routine can be further optimized in the future. Other ideas discussed: * A weak alias was discussed, but breaks for architectures that define their own implementations of memcmp since aliases to declarations are not permitted (only definitions). Arch-specific memcmp implementations typically declare memcmp in C headers, but implement them in assembly. * -ffreestanding also is used sporadically throughout the kernel. * -fno-builtin-bcmp doesn't work when doing LTO. Link: https://bugs.llvm.org/show_bug.cgi?id=41035 Link: https://code.woboq.org/userspace/glibc/string/memcmp.c.html#bcmp Link: https://github.com/llvm/llvm-project/commit/8e16d73346f8091461319a7dfc4ddd18eedcff13 Link: https://github.com/ClangBuiltLinux/linux/issues/416 Link: http://lkml.kernel.org/r/20190313211335.165605-1-ndesaulniers@google.com Signed-off-by: Nick Desaulniers Reported-by: Nathan Chancellor Reported-by: Adhemerval Zanella Suggested-by: Arnd Bergmann Suggested-by: James Y Knight Suggested-by: Masahiro Yamada Suggested-by: Nathan Chancellor Suggested-by: Rasmus Villemoes Acked-by: Steven Rostedt (VMware) Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Reviewed-by: Masahiro Yamada Reviewed-by: Andy Shevchenko Cc: David Laight Cc: Rasmus Villemoes Cc: Namhyung Kim Cc: Greg Kroah-Hartman Cc: Alexander Shishkin Cc: Dan Williams Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings

string: drop __must_check from strscpy()

2018-11-20T18:05:41Z

This was done as part of commit 08a77676f9c5 upstream, from which the following description is taken: > strlcpy() is worse than strlcpy() because it unconditionally runs > strlen() on the source string, and the only reason we switched to > strlcpy() here was because it was lacking __must_check, which doesn't > reflect any material differences between the two function. It's just > that someone added __must_check to strscpy() and not to strlcpy(). > > These basic string copy operations are used in variety of ways, and > one of not-so-uncommon use cases is safely handling truncated copies, > where the caller naturally doesn't care about the return value. The > __must_check doesn't match the actual use cases and forces users to > opt for inferior variants which lack __must_check by happenstance or > spread ugly (void) casts. Cc: Tejun Heo Signed-off-by: Ben Hutchings

string: provide strscpy()

2018-10-21T07:46:12Z

commit 30035e45753b708e7d47a98398500ca005e02b86 upstream. The strscpy() API is intended to be used instead of strlcpy(), and instead of most uses of strncpy(). - Unlike strlcpy(), it doesn't read from memory beyond (src + size). - Unlike strlcpy() or strncpy(), the API provides an easy way to check for destination buffer overflow: an -E2BIG error return value. - The provided implementation is robust in the face of the source buffer being asynchronously changed during the copy, unlike the current implementation of strlcpy(). - Unlike strncpy(), the destination buffer will be NUL-terminated if the string in the source buffer is too long. - Also unlike strncpy(), the destination buffer will not be updated beyond the NUL termination, avoiding strncpy's behavior of zeroing the entire tail end of the destination buffer. (A memset() after the strscpy() can be used if this behavior is desired.) - The implementation should be reasonably performant on all platforms since it uses the asm/word-at-a-time.h API rather than simple byte copy. Kernel-to-kernel string copy is not considered to be performance critical in any case. Signed-off-by: Chris Metcalf [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings

random: add and use memzero_explicit() for clearing data

2014-11-05T11:43:08Z

commit d4c5efdb97773f59a2b711754ca0953f24516739 upstream. zatimend has reported that in his environment (3.16/gcc4.8.3/corei7) memset() calls which clear out sensitive data in extract_{buf,entropy, entropy_user}() in random driver are being optimized away by gcc. Add a helper memzero_explicit() (similarly as explicit_bzero() variants) that can be used in such cases where a variable with sensitive data is being cleared out in the end. Other use cases might also be in crypto code. [ I have put this into lib/string.c though, as it's always built-in and doesn't need any dependencies then. ] Fixes kernel bugzilla: 82041 Reported-by: zatimend@hotmail.co.uk Signed-off-by: Daniel Borkmann Acked-by: Hannes Frederic Sowa Cc: Alexey Dobriyan Signed-off-by: Theodore Ts'o [ kamal: backport to 3.13-stable: one more memzero_explicit in extract_buf() ] Signed-off-by: Kamal Mostafa Signed-off-by: Luis Henriques

lib: add glibc style strchrnul() variant

2014-05-23T02:23:27Z

The strchrnul() variant helpfully returns a the end of the string instead of a NULL if the requested character is not found. This can simplify string parsing code since it doesn't need to expicitly check for a NULL return. If a valid string pointer is passed in, then a valid null terminated string will always come back out. Signed-off-by: Grant Likely

string: introduce helper to get base file name from given path

2012-12-18T01:15:17Z

There are several places in the kernel that use functionality like basename(3) with the exception: in case of '/foo/bar/' we expect to get an empty string. Let's do it common helper for them. Signed-off-by: Andy Shevchenko Cc: Jason Baron Cc: YAMANE Toshiaki Cc: Greg Kroah-Hartman Cc: Steven Rostedt Cc: Frederic Weisbecker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

UAPI: (Scripted) Disintegrate include/linux

2012-10-13T09:46:48Z

Signed-off-by: David Howells Acked-by: Arnd Bergmann Acked-by: Thomas Gleixner Acked-by: Michael Kerrisk Acked-by: Paul E. McKenney Acked-by: Dave Jones

string: do not export memweight() to userspace

2012-08-21T23:45:03Z

Fix the following warning: usr/include/linux/string.h:8: userspace cannot reference function or variable defined in the kernel Signed-off-by: WANG Cong Acked-by: Akinobu Mita Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

string: introduce memweight()

2012-07-31T00:25:16Z

memweight() is the function that counts the total number of bits set in memory area. Unlike bitmap_weight(), memweight() takes pointer and size in bytes to specify a memory area which does not need to be aligned to long-word boundary. [akpm@linux-foundation.org: rename `w' to `ret'] Signed-off-by: Akinobu Mita Cc: Anders Larsen Cc: Alasdair Kergon Cc: Laurent Pinchart Cc: Mark Fasheh Cc: Joel Becker Cc: Jan Kara Cc: Andreas Dilger Cc: "Theodore Ts'o" Cc: Matthew Wilcox Cc: Mauro Carvalho Chehab Cc: Tony Luck Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib/string.c: introduce memchr_inv()

2011-11-01T00:30:47Z

memchr_inv() is mainly used to check whether the whole buffer is filled with just a specified byte. The function name and prototype are stolen from logfs and the implementation is from SLUB. Signed-off-by: Akinobu Mita Acked-by: Christoph Lameter Acked-by: Pekka Enberg Cc: Matt Mackall Acked-by: Joern Engel Cc: Marcin Slusarz Cc: Eric Dumazet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds