| Message ID | 20220610233533.3649584-4-ira.weiny@intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | User pkey minor bug fixes | expand |
On 6/10/2022 4:35 PM, ira.weiny@intel.com wrote: > > +void test_pkey_alloc_on_unsupported_cpu(void) > +{ > + int test_pkey = sys_pkey_alloc(0, 0); > + > + dprintf1("pkey_alloc: %d (%d %s)\n", test_pkey, errno, > + strerror(errno)); > + pkey_assert(test_pkey < 0); > + pkey_assert(errno == ENOSPC); This assert fails on a kernel with CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS disabled. Since pkey_alloc() is an architecture dependent syscall, ENOSYS is returned instead of ENOSPC when support is disabled at compile time. See kernel/sys_ni.c This brings us to an interesting question. Should we have different return error codes when compile support is disabled vs when runtime support is missing? Here is the current behavior for pkey_alloc(): No compile time support -> return ENOSYS No runtime support (but compile time support present) -> return ENOSPC I would think applications would prefer the same error code. But, I am not sure if we can achieve this now due to ABI reasons. > +} > +
On 6/16/22 12:25, Sohil Mehta wrote: > Should we have different return error codes when compile support is > disabled vs when runtime support is missing? It doesn't *really* matter. Programs have to be able to run on old kernels which will return ENOSYS. So, _when_ new kernels return ENOSYS or ENOSPC is pretty immaterial.
diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c index 43e47de19c0d..4b733a75606f 100644 --- a/tools/testing/selftests/vm/protection_keys.c +++ b/tools/testing/selftests/vm/protection_keys.c @@ -1554,6 +1554,16 @@ void test_implicit_mprotect_exec_only_memory(int *ptr, u16 pkey) do_not_expect_pkey_fault("plain read on recently PROT_EXEC area"); } +void test_pkey_alloc_on_unsupported_cpu(void) +{ + int test_pkey = sys_pkey_alloc(0, 0); + + dprintf1("pkey_alloc: %d (%d %s)\n", test_pkey, errno, + strerror(errno)); + pkey_assert(test_pkey < 0); + pkey_assert(errno == ENOSPC); +} + void test_mprotect_pkey_on_unsupported_cpu(int *ptr, u16 pkey) { int size = PAGE_SIZE; @@ -1688,6 +1698,8 @@ int main(int argc, char *argv[]) printf("running PKEY tests for unsupported CPU/OS\n"); + test_pkey_alloc_on_unsupported_cpu(); + ptr = mmap(NULL, size, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); assert(ptr != (void *)-1); test_mprotect_pkey_on_unsupported_cpu(ptr, 1);