When unregistering the signal handler, we have to pass SIG_DFL, and
blindly reading from PFN 0 and PFN 1 seems to be problematic on !x86
systems. In particularly, on arm64 tx2 machines where noting resides at
these physical memory locations, we can generate RAS errors.
Let's fix it by scanning /proc/iomem for actual "System RAM".
Link: https://lkml.kernel.org/r/20250528195244.1182810-1-david@redhat.com
Fixes: 2616b37032 ("selftests/mm: add simple VM_PFNMAP tests based on mmap'ing /dev/mem")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reported-by: Ryan Roberts <ryan.roberts@arm.com>
Closes: https://lore.kernel.org/all/232960c2-81db-47ca-a337-38c4bce5f997@arm.com/T/#u
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Aishwarya TCV <aishwarya.tcv@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's test some basic functionality using /dev/mem. These tests will
implicitly cover some PAT (Page Attribute Handling) handling on x86.
These tests will only run when /dev/mem access to the first two pages in
physical address space is possible and allowed; otherwise, the tests are
skipped.
On current x86-64 with PAT inside a VM, all tests pass:
TAP version 13
1..6
# Starting 6 tests from 1 test cases.
# RUN pfnmap.madvise_disallowed ...
# OK pfnmap.madvise_disallowed
ok 1 pfnmap.madvise_disallowed
# RUN pfnmap.munmap_split ...
# OK pfnmap.munmap_split
ok 2 pfnmap.munmap_split
# RUN pfnmap.mremap_fixed ...
# OK pfnmap.mremap_fixed
ok 3 pfnmap.mremap_fixed
# RUN pfnmap.mremap_shrink ...
# OK pfnmap.mremap_shrink
ok 4 pfnmap.mremap_shrink
# RUN pfnmap.mremap_expand ...
# OK pfnmap.mremap_expand
ok 5 pfnmap.mremap_expand
# RUN pfnmap.fork ...
# OK pfnmap.fork
ok 6 pfnmap.fork
# PASSED: 6 / 6 tests passed.
# Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0
However, we are able to trigger:
[ 27.888251] x86/PAT: pfnmap:1790 freeing invalid memtype [mem 0x00000000-0x00000fff]
There are probably more things worth testing in the future, such as
MAP_PRIVATE handling. But this set of tests is sufficient to cover most
of the things we will rework regarding PAT handling.
Link: https://lkml.kernel.org/r/20250509153033.952746-1-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Dev Jain <dev.jain@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
