From: Francis Laniel <laniel_fran...@privacyrequired.com> Hi.
First, I hope your families, friends and yourself are fine. In a recent mail about the merge of a new fortified string function, Linus Torvalds suggested the creation of a dedicated header file for these functions: https://marc.info/?l=linux-mm-commits&m=160810366111244 This will make the code cleaner and also improve compile time for people who do not set CONFIG_FORTIFY_SOURCE. So, this patch creates fortify-string.h which is a new header which contains all the fortified versions of functions declared in string.h. Since code was moved, I might as well correct the warnings raised by checkpatch.pl. I benchmarked the code compilation with and without CONFIG_FORTIFY_SOURCE. To do this, I compiled 10 times a x86_64_defconfig'ured kernel using make -j4 and cleaning after each compilation. These compilations were first done without CONFIG_FORTIFY_SOURCE defined, then with this option defined. The results were collected using the time bash builtin and are the following (in seconds, rounded to 10^-3): | | min | max | mean | std. dev. | median | 99th percentile | | --- | ------- | ------- | ------- | --------- | ------- | --------------- | | w/o | 524.488 | 526.982 | 525.111 | 0.722 | 524.901 | 526.848 | | w/ | 529.502 | 531.795 | 529.939 | 0.671 | 529.783 | 531.633 | First, the results are quite stable as shown by the standard deviation (less than 1 second). On average, compile time without CONFIG_FORTIFY_SOURCE is 0.919% faster. For the median case, compiling without setting this option is 0.930% faster. Finally, with the 99th percentile, not using CONFIG_FORTIFY_SOURCE is 0.908% faster. Globally, using a different header seems to provide a roughly 1% faster compile time for people who do not set CONFIG_FORTIFY_SOURCE. This is not a huge gain... but still a gain! Especially on compilation which is an operation kernel developers do a lot. So, I await your opinions and reviews on this patch. Version history: * v2: Correct misguarded instructions which follow if. Best regards. Francis Laniel (1): string.h: Move fortified functions definitions in a dedicated header. include/linux/fortify-string.h | 302 +++++++++++++++++++++++++++++++++ include/linux/string.h | 282 +----------------------------- 2 files changed, 303 insertions(+), 281 deletions(-) create mode 100644 include/linux/fortify-string.h -- 2.20.1
