On Mon, Feb 8, 2021 at 11:10 PM David Gow davidgow@google.com wrote:
kunit_tool maintains a list of config options which are broken under UML, which we exclude from an otherwise 'make ARCH=um allyesconfig' build used to run all tests with the --alltests option.
Something in UML allyesconfig is causing segfaults when page poisining is enabled (and is poisoning with a non-zero value). Previously, this didn't occur, as allyesconfig enabled the CONFIG_PAGE_POISONING_ZERO option, which worked around the problem by zeroing memory. This option has since been removed, and memory is now poisoned with 0xAA, which triggers segfaults in many different codepaths, preventing UML from booting.
Note that we have to disable both CONFIG_PAGE_POISONING and CONFIG_DEBUG_PAGEALLOC, as the latter will 'select' the former on architectures (such as UML) which don't implement __kernel_map_pages().
Ideally, we'd fix this properly by tracking down the real root cause, but since this is breaking KUnit's --alltests feature, it's worth disabling there in the meantime so the kernel can boot to the point where tests can actually run.
Fixes: f289041ed4 ("mm, page_poison: remove CONFIG_PAGE_POISONING_ZERO") Signed-off-by: David Gow davidgow@google.com
Reviewed-by: Brendan Higgins brendanhiggins@google.com