On Wed, Jun 15, 2016 at 1:44 PM, Mark Rutland <[email protected]> wrote: > 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: >> > On Tue, Jun 14, 2016 at 7:55 PM, Mark Rutland <[email protected]> wrote: >> > > 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@ribbensteg:/home/nanook# ./kcov > mmap: No such device > > The device exists (it was able to open the fd, evidently): > > root@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? According to Dmitry (thanks, Dmitry!) this has regressed recently, but there's a pending patch that should probably fix the problem: http://lkml.iu.edu/hypermail/linux/kernel/1605.2/04379.html > Thanks, > Mark.
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