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Filename Latest commit message Latest commit date
Steven Rostedt (VMware) 72921427d4 string.h: Add str_has_prefix() helper function
A discussion came up in the trace triggers thread about converting a
bunch of:

 strncmp(str, "const", sizeof("const") - 1)

use cases into a helper macro. It started with:

	strncmp(str, const, sizeof(const) - 1)

But then Joe Perches mentioned that if a const is not used, the
sizeof() will be the size of a pointer, which can be bad. And that
gcc will optimize strlen("const") into "sizeof("const") - 1".

Thinking about this more, a quick grep in the kernel tree found several
(thousands!) of cases that use this construct. A quick grep also
revealed that there's probably several bugs in that use case. Some are
that people forgot the "- 1" (which I found) and others could be that
the constant for the sizeof is different than the constant (although, I
haven't found any of those, but I also didn't look hard).

I figured the best thing to do is to create a helper macro and place it
into include/linux/string.h. And go around and fix all the open coded
versions of it later.

Note, gcc appears to optimize this when we make it into an always_inline
static function, which removes a lot of issues that a macro produces.

Link: http://lkml.kernel.org/r/e3e754f2bd18e56eaa8baf79bee619316ebf4cfc.1545161087.git.tom.zanussi@linux.intel.com
Link: http://lkml.kernel.org/r/20181219211615.2298e781@gandalf.local.home
Link: http://lkml.kernel.org/r/CAHk-=wg_sR-UEC1ggmkZpypOUYanL5CMX4R7ceuaV4QMf5jBtg@mail.gmail.com

Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Suggestions-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggestions-by: Joe Perches <joe@perches.com>
Suggestions-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-12-22 22:50:29 -05:00
arch arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack 2018-12-22 08:21:02 -05:00
block
certs
crypto
Documentation tracing/uprobes: Use dyn_event framework for uprobe events 2018-12-08 20:54:10 -05:00
drivers libnvdimm 4.20-rc3 2018-11-18 12:21:09 -08:00
firmware
fs
include string.h: Add str_has_prefix() helper function 2018-12-22 22:50:29 -05:00
init
ipc
kernel tracing: Make function ‘ftrace_exports’ static 2018-12-22 08:21:06 -05:00
lib seq_buf: Use size_t for len in seq_buf_puts() 2018-12-22 08:21:03 -05:00
LICENSES
mm
net
samples
scripts scripts/recordmcount.{c,pl}: support -ffunction-sections .text.* section names 2018-12-08 20:54:08 -05:00
security
sound
tools selftests/ftrace: Add testcases for dynamic event 2018-12-10 12:22:44 -05:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 4.20-rc3 2018-11-18 13:33:44 -08:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.