On Tue, Nov 26, 2024 at 02:34:47PM +0100, Maciej Wieczor-Retman wrote: > Recent change in how get_user() handles pointers [1] has a specific case > for LAM. It assigns a different bitmask that's later used to check > whether a pointer comes from userland in get_user(). > > While currently commented out (until LASS [2] is merged into the kernel) > it's worth making changes to the LAM selftest ahead of time. > > Modify cpu_has_la57() so it provides current paging level information > instead of the cpuid one. > > Add test case to LAM that utilizes a ioctl (FIOASYNC) syscall which uses > get_user() in its implementation. Execute the syscall with differently > tagged pointers to verify that valid user pointers are passing through > and invalid kernel/non-canonical pointers are not. > > Also to avoid unhelpful test failures add a check in main() to skip > running tests if LAM was not compiled into the kernel. > > Code was tested on a Sierra Forest Xeon machine that's LAM capable. The > test was ran without issues with both the LAM lines from [1] untouched > and commented out. The test was also ran without issues with LAM_SUP > both enabled and disabled. > > 4/5 level pagetables code paths were also successfully tested in Simics > on a 5-level capable machine. > > [1] https://lore.kernel.org/all/20241024013214.129639-1-torvalds@xxxxxxxxxxxxxxxxxxxx/ > [2] https://lore.kernel.org/all/20241028160917.1380714-1-alexander.shishkin@xxxxxxxxxxxxxxx/ > > Maciej Wieczor-Retman (3): > selftests/lam: Move cpu_has_la57() to use cpuinfo flag > selftests/lam: Skip test if LAM is disabled > selftests/lam: Test get_user() LAM pointer handling > > tools/testing/selftests/x86/lam.c | 122 ++++++++++++++++++++++++++++-- > 1 file changed, 117 insertions(+), 5 deletions(-) Apart from the nitpick in 1/3, looks good to me: Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> -- Kiryl Shutsemau / Kirill A. Shutemov
