From: Dave Hansen <[email protected]> Protection key 0 is the default key for all memory and will not normally come back from pkey_alloc(). But, you might still want pass it to mprotect_pkey().
This check ensures that you can use pkey 0. Signed-off-by: Dave Hansen <[email protected]> Cc: Ram Pai <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Michael Ellermen <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Shuah Khan <[email protected]> --- b/tools/testing/selftests/x86/protection_keys.c | 30 ++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff -puN tools/testing/selftests/x86/protection_keys.c~pkeys-update-selftests-with-pkey-0-test tools/testing/selftests/x86/protection_keys.c --- a/tools/testing/selftests/x86/protection_keys.c~pkeys-update-selftests-with-pkey-0-test 2018-03-26 10:22:34.841170194 -0700 +++ b/tools/testing/selftests/x86/protection_keys.c 2018-03-26 10:22:34.844170194 -0700 @@ -1169,6 +1169,35 @@ void test_pkey_alloc_exhaust(int *ptr, u } } +/* + * pkey 0 is special. It is allocated by default, so you do not + * have to call pkey_alloc() to use it first. Make sure that it + * is usable. + */ +void test_mprotect_with_pkey_0(int *ptr, u16 pkey) +{ + long size; + int prot; + + assert(pkey_last_malloc_record); + size = pkey_last_malloc_record->size; + /* + * This is a bit of a hack. But mprotect() requires + * huge-page-aligned sizes when operating on hugetlbfs. + * So, make sure that we use something that's a multiple + * of a huge page when we can. + */ + if (size >= HPAGE_SIZE) + size = HPAGE_SIZE; + prot = pkey_last_malloc_record->prot; + + /* Use pkey 0 */ + mprotect_pkey(ptr, size, prot, 0); + + /* Make sure that we can set it back to the original pkey. */ + mprotect_pkey(ptr, size, prot, pkey); +} + void test_ptrace_of_child(int *ptr, u16 pkey) { __attribute__((__unused__)) int peek_result; @@ -1306,6 +1335,7 @@ void (*pkey_tests[])(int *ptr, u16 pkey) test_kernel_gup_of_access_disabled_region, test_kernel_gup_write_to_write_disabled_region, test_executing_on_unreadable_memory, + test_mprotect_with_pkey_0, test_ptrace_of_child, test_pkey_syscalls_on_non_allocated_pkey, test_pkey_syscalls_bad_args, _
