Add a man page for kcov.

[gbe]

Good to go from manpages!

It would maybe feasible to include a notice about incompatibles about other kernel santinzing options.
I remember that I tried to build a kernel once with following options, which was not possible:

include GENERIC
ident GENERIC-SANTI
options		COVERAGE
options		KCOV
options		KCSAN

[markj]

In D26108#579497, @gbe wrote:

Good to go from manpages!

It would maybe feasible to include a notice about incompatibles about other kernel santinzing options.
I remember that I tried to build a kernel once with following options, which was not possible:

include GENERIC
ident GENERIC-SANTI
options		COVERAGE
options		KCOV
options		KCSAN

Yeah, I guess you can only build with a single sanitizer at a time. Since KCSAN is itself not yet documented, I'm inclined to just leave the KCOV page as-is. Once I've gotten a chance to try using KCSAN I might try documenting it.

[tuexen]

Maybe you can mention that it is only supported on amd64 and arm64, possibly in the BUGS section.

[andrew]

In D26108#579767, @tuexen wrote:

Maybe you can mention that it is only supported on amd64 and arm64, possibly in the BUGS section.

It should work on all architectures. The only issue I know about is on 32-bit mips where we don't have the userspace 64-bit atomic operations to clear buf[0].

share/man/man4/kcov.4

177 ↗

(On Diff #75956)

It might pay to zero buf[0] before the printf otherwise the return path of the ioctl will also be in the trace.

[tuexen]

In D26108#579813, @andrew wrote:

In D26108#579767, @tuexen wrote:

Maybe you can mention that it is only supported on amd64 and arm64, possibly in the BUGS section.

It should work on all architectures.

Thanks for the clarification. For whatever reason I was assuming that it works only on amd64 and arm64. Not sure why...

[andrew]

In D26108#579497, @gbe wrote:

Good to go from manpages!

It would maybe feasible to include a notice about incompatibles about other kernel santinzing options.
I remember that I tried to build a kernel once with following options, which was not possible:

include GENERIC
ident GENERIC-SANTI
options		COVERAGE
options		KCOV
options		KCSAN

It should be possible to mix them with clang 11 or gcc.

[markj]

Clear the tracing buffer after ioctl(KIOENABLE).