b3c0d957a2
When building with KCOV enabled the compiler will insert function calls to probes allowing us to trace the execution of the kernel from userspace. These probes are on function entry (trace-pc) and on comparison operations (trace-cmp). Userspace can enable the use of these probes on a single kernel thread with an ioctl interface. It can allocate space for the probe with KIOSETBUFSIZE, then mmap the allocated buffer and enable tracing with KIOENABLE, with the trace mode being passed in as the int argument. When complete KIODISABLE is used to disable tracing. The first item in the buffer is the number of trace event that have happened. Userspace can write 0 to this to reset the tracing, and is expected to do so on first use. The format of the buffer depends on the trace mode. When in PC tracing just the return address of the probe is stored. Under comparison tracing the comparison type, the two arguments, and the return address are traced. The former method uses on entry per trace event, while the later uses 4. As such they are incompatible so only a single mode may be enabled. KCOV is expected to help fuzzing the kernel, and while in development has already found a number of issues. It is required for the syzkaller system call fuzzer [1]. Other kernel fuzzers could also make use of it, either with the current interface, or by extending it with new modes. A man page is currently being worked on and is expected to be committed soon, however having the code in the kernel now is useful for other developers to use. [1] https://github.com/google/syzkaller Submitted by: Mitchell Horne <mhorne063@gmail.com> (Earlier version) Reviewed by: kib Testing by: tuexen Sponsored by: DARPA, AFRL Sponsored by: The FreeBSD Foundation (Mitchell Horne) Differential Revision: https://reviews.freebsd.org/D14599 |
||
---|---|---|
.. | ||
etc | ||
freebsd_test_suite | ||
sys | ||
Kyuafile | ||
Makefile | ||
Makefile.depend | ||
Makefile.inc0 | ||
README |
src/tests: The FreeBSD test suite ================================= To run the FreeBSD test suite: (1) Make sure that kyua is installed: pkg install kyua (2) To run the tests: kyua test -k /usr/tests/Kyuafile (3) To see the test results: kyua report For further information on using the test suite, read tests(7): man tests Description of FreeBSD test suite ================================= The build of the test suite is organized in the following manner: * The build of all test artifacts is protected by the MK_TESTS knob. The user can disable these with the WITHOUT_TESTS setting in src.conf(5). * The goal for /usr/tests/ (the installed test programs) is to follow the same hierarchy as /usr/src/ wherever possible, which in turn drives several of the design decisions described below. This simplifies the discoverability of tests. We want a mapping such as: /usr/src/bin/cp/ -> /usr/tests/bin/cp/ /usr/src/lib/libc/ -> /usr/tests/lib/libc/ /usr/src/usr.bin/cut/ -> /usr/tests/usr.bin/cut/ ... and many more ... * Test programs for specific utilities and libraries are located next to the source code of such programs. For example, the tests for the src/lib/libcrypt/ library live in src/lib/libcrypt/tests/. The tests/ subdirectory is optional and should, in general, be avoided. * The src/tests/ hierarchy (this directory) provides generic test infrastructure and glue code to join all test programs together into a single test suite definition. * The src/tests/ hierarchy also includes cross-functional test programs: i.e. test programs that cover more than a single utility or library and thus don't fit anywhere else in the tree. Consider this to follow the same rationale as src/share/man/: this directory contains generic manual pages while the manual pages that are specific to individual tools or libraries live next to the source code. In order to keep the src/tests/ hierarchy decoupled from the actual test programs being installed --which is a worthy goal because it simplifies the addition of new test programs and simplifies the maintenance of the tree-- the top-level Kyuafile does not know which subdirectories may exist upfront. Instead, such Kyuafile automatically detects, at run-time, which */Kyuafile files exist and uses those directly. Similarly, every directory in src/ that wants to install a Kyuafile to just recurse into other subdirectories reuses this Kyuafile with auto-discovery features. As an example, take a look at src/lib/tests/ whose sole purpose is to install a Kyuafile into /usr/tests/lib/. The goal in this specific case is for /usr/tests/lib/ to be generated entirely from src/lib/. -- $FreeBSD$