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 |
||
|---|---|---|
| .. | ||
| acct | ||
| execve | ||
| pipe | ||
| coredump_phnum_helper.c | ||
| coredump_phnum_test.sh | ||
| kcov.c | ||
| kern_copyin.c | ||
| kern_descrip_test.c | ||
| libkern_crc32.c | ||
| Makefile | ||
| Makefile.depend | ||
| Makefile.inc | ||
| pdeathsig_helper.c | ||
| pdeathsig.c | ||
| ptrace_test.c | ||
| reaper.c | ||
| sigaltstack.c | ||
| sys_getrandom.c | ||
| unix_passfd_test.c | ||
| unix_seqpacket_test.c | ||
| unix_socketpair_test.c | ||
| waitpid_nohang.c | ||