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Subject[PATCH 3/9] x86, pkeys, selftests: add a test for pkey 0
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From: Dave Hansen <dave.hansen@linux.intel.com>

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 <dave.hansen@linux.intel.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Michael Ellermen <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Shuah Khan <shuah@kernel.org>
---

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 2018-03-21 15:47:49.273198924 -0700
+++ b/tools/testing/selftests/x86/protection_keys.c 2018-03-21 15:47:49.277198924 -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,
_
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