[v2 4/5] arm64: mte: add a test for MTE tags compression

[Alexander Potapenko]

Ensure that tag sequences containing alternating values are compressed
to buffers of expected size and correctly decompressed afterwards.

Signed-off-by: Alexander Potapenko <glider at google.com>
---
 arch/arm64/Kconfig           |  10 ++
 arch/arm64/mm/Makefile       |   1 +
 arch/arm64/mm/test_mtecomp.c | 175 +++++++++++++++++++++++++++++++++++
 3 files changed, 186 insertions(+)
 create mode 100644 arch/arm64/mm/test_mtecomp.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0aa727888e746..9473c1e2e8593 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2101,6 +2101,16 @@ config ARM64_MTE_COMP
 	  128-byte tag buffers corresponding to 4K pages can be compressed using
 	  the EA0 algorithm to save heap memory.
 
+config ARM64_MTE_COMP_KUNIT_TEST
+	tristate "Test tag compression for ARM64 MTE" if !KUNIT_ALL_TESTS
+	default KUNIT_ALL_TESTS
+	depends on KUNIT && ARM64_MTE_COMP
+	help
+	  Test EA0 compression algorithm enabled by CONFIG_ARM64_MTE_COMP.
+
+	  Ensure that tag sequences containing alternating values are compressed
+	  to buffers of expected size and correctly decompressed afterwards.
+
 config ARM64_SVE
 	bool "ARM Scalable Vector Extension support"
 	default y
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index 46778f6dd83c2..170dc62b010b9 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_TRANS_TABLE)	+= trans_pgd-asm.o
 obj-$(CONFIG_DEBUG_VIRTUAL)	+= physaddr.o
 obj-$(CONFIG_ARM64_MTE)		+= mteswap.o
 obj-$(CONFIG_ARM64_MTE_COMP)	+= mtecomp.o
+obj-$(CONFIG_ARM64_MTE_COMP_KUNIT_TEST) += test_mtecomp.o
 KASAN_SANITIZE_physaddr.o	+= n
 
 obj-$(CONFIG_KASAN)		+= kasan_init.o
diff --git a/arch/arm64/mm/test_mtecomp.c b/arch/arm64/mm/test_mtecomp.c
new file mode 100644
index 0000000000000..67bef6f28dac4
--- /dev/null
+++ b/arch/arm64/mm/test_mtecomp.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test cases for EA0, the compression algorithm for MTE tags.
+ */
+
+#include <asm/mtecomp.h>
+#include <kunit/test.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+/*
+ * Test that ea0_tags_to_ranges() produces a single range for a zero-filled tag
+ * buffer.
+ */
+static void test_tags_to_ranges_zero(struct kunit *test)
+{
+	u8 tags[128], dtags[128];
+	short r_sizes[256];
+	int r_len = 256;
+	u8 r_tags[256];
+
+	memset(tags, 0, 128);
+	ea0_tags_to_ranges(tags, r_tags, r_sizes, &r_len);
+	KUNIT_EXPECT_EQ(test, r_len, 1);
+	KUNIT_EXPECT_EQ(test, r_tags[0], 0);
+	KUNIT_EXPECT_EQ(test, r_sizes[0], 256);
+	ea0_ranges_to_tags(r_tags, r_sizes, r_len, dtags);
+	KUNIT_EXPECT_EQ(test, memcmp(tags, dtags, 128), 0);
+}
+
+/*
+ * Test that a small number of different tags is correctly transformed into
+ * ranges.
+ */
+static void test_tags_to_ranges_simple(struct kunit *test)
+{
+	u8 tags[128], dtags[128];
+	const u8 ex_tags[] = { 0xa, 0x0, 0xa, 0xb, 0x0 };
+	const short ex_sizes[] = { 1, 2, 2, 1, 250 };
+	short r_sizes[256];
+	int r_len = 256;
+	u8 r_tags[256];
+
+	memset(tags, 0, 128);
+	tags[0] = 0xa0;
+	tags[1] = 0x0a;
+	tags[2] = 0xab;
+	ea0_tags_to_ranges(tags, r_tags, r_sizes, &r_len);
+	KUNIT_EXPECT_EQ(test, r_len, 5);
+	KUNIT_EXPECT_EQ(test, memcmp(r_tags, ex_tags, sizeof(ex_tags)), 0);
+	KUNIT_EXPECT_EQ(test, memcmp(r_sizes, ex_sizes, sizeof(ex_sizes)), 0);
+	ea0_ranges_to_tags(r_tags, r_sizes, r_len, dtags);
+	KUNIT_EXPECT_EQ(test, memcmp(tags, dtags, 128), 0);
+}
+
+/* Test that repeated 0xa0 byte produces 256 ranges of length 1. */
+static void test_tags_to_ranges_repeated(struct kunit *test)
+{
+	u8 tags[128], dtags[128];
+	short r_sizes[256];
+	int r_len = 256;
+	u8 r_tags[256];
+
+	memset(tags, 0xa0, 128);
+	ea0_tags_to_ranges(tags, r_tags, r_sizes, &r_len);
+	KUNIT_EXPECT_EQ(test, r_len, 256);
+	ea0_ranges_to_tags(r_tags, r_sizes, r_len, dtags);
+	KUNIT_EXPECT_EQ(test, memcmp(tags, dtags, 128), 0);
+}
+
+/* Test that a zero-filled array is compressed into inline storage. */
+static void test_compress_zero(struct kunit *test)
+{
+	u8 tags[128], dtags[128];
+	u64 handle;
+
+	memset(tags, 0, 128);
+	handle = ea0_compress(tags);
+	KUNIT_EXPECT_EQ(test, handle & BIT_ULL(63), 0);
+	/* Tags are stored inline. */
+	KUNIT_EXPECT_EQ(test, ea0_storage_size(handle), 8);
+	KUNIT_EXPECT_TRUE(test, ea0_decompress(handle, dtags));
+	KUNIT_EXPECT_EQ(test, memcmp(tags, dtags, 128), 0);
+}
+
+/*
+ * Test that a very small number of tag ranges ends up compressed into 8 bytes.
+ */
+static void test_compress_simple(struct kunit *test)
+{
+	u8 tags[128], dtags[128];
+	u64 handle;
+
+	memset(tags, 0, 128);
+	tags[0] = 0xa0;
+	tags[1] = 0x0a;
+	tags[2] = 0xab;
+
+	handle = ea0_compress(tags);
+	KUNIT_EXPECT_EQ(test, handle & BIT_ULL(63), 0);
+	/* Tags are stored inline. */
+	KUNIT_EXPECT_EQ(test, ea0_storage_size(handle), 8);
+	KUNIT_EXPECT_TRUE(test, ea0_decompress(handle, dtags));
+	KUNIT_EXPECT_EQ(test, memcmp(tags, dtags, 128), 0);
+}
+
+/*
+ * Generate a buffer that will contain @nranges of tag ranges, test that it
+ * compresses into @exp_size bytes and decompresses into the original tag
+ * sequence.
+ */
+static void compress_range_helper(struct kunit *test, int nranges, int exp_size)
+{
+	u8 tags[128], dtags[128];
+	u64 handle;
+	int i;
+
+	memset(tags, 0, 128);
+
+	if (nranges > 1) {
+		nranges--;
+		for (i = 0; i < nranges / 2; i++)
+			tags[i] = 0xab;
+		if (nranges % 2)
+			tags[nranges / 2] = 0xa0;
+	}
+
+	handle = ea0_compress(tags);
+	KUNIT_EXPECT_EQ(test, handle & BIT_ULL(63), 0);
+	KUNIT_EXPECT_EQ(test, ea0_storage_size(handle), exp_size);
+	KUNIT_EXPECT_TRUE(test, ea0_decompress(handle, dtags));
+	KUNIT_EXPECT_EQ(test, memcmp(tags, dtags, 128), 0);
+}
+
+/*
+ * Test that every number of tag ranges is correctly compressed and
+ * decompressed.
+ */
+static void test_compress_ranges(struct kunit *test)
+{
+	int i, exp_size;
+
+	for (i = 1; i <= 256; i++) {
+		if (i < 7)
+			exp_size = 8;
+		else if (i < 12)
+			exp_size = 16;
+		else if (i < 24)
+			exp_size = 32;
+		else if (i < 47)
+			exp_size = 64;
+		else
+			exp_size = 128;
+		compress_range_helper(test, i, exp_size);
+	}
+}
+
+static struct kunit_case mtecomp_test_cases[] = {
+	KUNIT_CASE(test_tags_to_ranges_zero),
+	KUNIT_CASE(test_tags_to_ranges_simple),
+	KUNIT_CASE(test_tags_to_ranges_repeated),
+	KUNIT_CASE(test_compress_zero),
+	KUNIT_CASE(test_compress_simple),
+	KUNIT_CASE(test_compress_ranges),
+	{}
+};
+
+static struct kunit_suite mtecomp_test_suite = {
+	.name = "mtecomp",
+	.test_cases = mtecomp_test_cases,
+};
+kunit_test_suites(&mtecomp_test_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexander Potapenko <glider at google.com>");
-- 
2.41.0.255.g8b1d071c50-goog