On Wed, Jun 15, 2016 at 10:25:10AM +0100, Mark Rutland wrote:

On Tue, Jun 14, 2016 at 08:16:08PM +0200, Alexander Potapenko wrote:

quoted

On Tue, Jun 14, 2016 at 7:55 PM, Mark Rutland [off-list ref] wrote:

quoted

I built and booted (via EFI) a kernel with this feature enabled (also
with the boot/Makefile change removed). I haven't tested the feature
itself as such, as I'm not sure how to do that.

You can test it by running the test program from Documentation/kcov.txt.

Ah, I hadn't spotted that. If I get the chance I'll try to give that a
go.

I just had a go (with this applied atop of v4.7-rc3), and I get:

root at ribbensteg:/home/nanook# ./kcov 
mmap: No such device

The device exists (it was able to open the fd, evidently):

root at ribbensteg:/home/nanook# ls -al /sys/kernel/debug/kcov 
-rw------- 1 root root 0 Jan  1  1970 /sys/kernel/debug/kcov

Strace show me:

openat(AT_FDCWD, "/sys/kernel/debug/kcov", O_RDWR) = 3
ioctl(3, CHIOMOVE or CM_IOCGATR, 0x10000) = 0
mmap(NULL, 524288, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0) = -1 ENODEV (No such device)

It doesn't look like the error paths in kcov_mmap are hitting.

Any ideas?

Thanks,
Mark.