diff --git a/tools/testing/memblock/tests/alloc_api.c b/tools/testing/memblock/tests/alloc_api.c
index a14f38eb8a89..71c89cb9b2a8 100644
--- a/tools/testing/memblock/tests/alloc_api.c
+++ b/tools/testing/memblock/tests/alloc_api.c
@@ -22,6 +22,8 @@ static int alloc_top_down_simple_check(void)
 	allocated_ptr = memblock_alloc(size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, size);
+
 	ASSERT_EQ(rgn->size, size);
 	ASSERT_EQ(rgn->base, expected_start);
 
@@ -80,6 +82,8 @@ static int alloc_top_down_disjoint_check(void)
 	allocated_ptr = memblock_alloc(r2_size, alignment);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r2_size);
+
 	ASSERT_EQ(rgn1->size, r1.size);
 	ASSERT_EQ(rgn1->base, r1.base);
 
@@ -125,6 +129,8 @@ static int alloc_top_down_before_check(void)
 	allocated_ptr = memblock_alloc(r2_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r2_size);
+
 	ASSERT_EQ(rgn->size, total_size);
 	ASSERT_EQ(rgn->base, memblock_end_of_DRAM() - total_size);
 
@@ -173,6 +179,8 @@ static int alloc_top_down_after_check(void)
 	allocated_ptr = memblock_alloc(r2_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r2_size);
+
 	ASSERT_EQ(rgn->size, total_size);
 	ASSERT_EQ(rgn->base, r1.base - r2_size);
 
@@ -223,6 +231,8 @@ static int alloc_top_down_second_fit_check(void)
 	allocated_ptr = memblock_alloc(r3_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r3_size);
+
 	ASSERT_EQ(rgn->size, r2.size + r3_size);
 	ASSERT_EQ(rgn->base, r2.base - r3_size);
 
@@ -277,6 +287,8 @@ static int alloc_in_between_generic_check(void)
 	allocated_ptr = memblock_alloc(r3_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r3_size);
+
 	ASSERT_EQ(rgn->size, total_size);
 	ASSERT_EQ(rgn->base, r1.base - r2.size - r3_size);
 
@@ -418,6 +430,8 @@ static int alloc_limited_space_generic_check(void)
 	allocated_ptr = memblock_alloc(available_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, available_size);
+
 	ASSERT_EQ(rgn->size, MEM_SIZE);
 	ASSERT_EQ(rgn->base, memblock_start_of_DRAM());
 
@@ -442,6 +456,7 @@ static int alloc_no_memory_generic_check(void)
 	PREFIX_PUSH();
 
 	reset_memblock_regions();
+	fill_memblock();
 
 	allocated_ptr = memblock_alloc(SZ_1K, SMP_CACHE_BYTES);
 
@@ -472,6 +487,8 @@ static int alloc_bottom_up_simple_check(void)
 	allocated_ptr = memblock_alloc(SZ_2, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, SZ_2);
+
 	ASSERT_EQ(rgn->size, SZ_2);
 	ASSERT_EQ(rgn->base, memblock_start_of_DRAM());
 
@@ -528,6 +545,7 @@ static int alloc_bottom_up_disjoint_check(void)
 	allocated_ptr = memblock_alloc(r2_size, alignment);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r2_size);
 
 	ASSERT_EQ(rgn1->size, r1.size);
 	ASSERT_EQ(rgn1->base, r1.base);
@@ -571,6 +589,8 @@ static int alloc_bottom_up_before_check(void)
 	allocated_ptr = memblock_alloc(r1_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r1_size);
+
 	ASSERT_EQ(rgn->size, total_size);
 	ASSERT_EQ(rgn->base, memblock_start_of_DRAM());
 
@@ -618,6 +638,8 @@ static int alloc_bottom_up_after_check(void)
 	allocated_ptr = memblock_alloc(r2_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r2_size);
+
 	ASSERT_EQ(rgn->size, total_size);
 	ASSERT_EQ(rgn->base, r1.base);
 
@@ -669,6 +691,8 @@ static int alloc_bottom_up_second_fit_check(void)
 	allocated_ptr = memblock_alloc(r3_size, SMP_CACHE_BYTES);
 
 	ASSERT_NE(allocated_ptr, NULL);
+	ASSERT_MEM_EQ((char *)allocated_ptr, 0, r3_size);
+
 	ASSERT_EQ(rgn->size, r2.size + r3_size);
 	ASSERT_EQ(rgn->base, r2.base);
 
diff --git a/tools/testing/memblock/tests/common.c b/tools/testing/memblock/tests/common.c
index 76a8ad818f3a..0ca26fe12c38 100644
--- a/tools/testing/memblock/tests/common.c
+++ b/tools/testing/memblock/tests/common.c
@@ -60,16 +60,23 @@ void reset_memblock_attributes(void)
 	memblock.current_limit	= MEMBLOCK_ALLOC_ANYWHERE;
 }
 
+void fill_memblock(void)
+{
+	memset(memory_block.base, 1, MEM_SIZE);
+}
+
 void setup_memblock(void)
 {
 	reset_memblock_regions();
 	memblock_add((phys_addr_t)memory_block.base, MEM_SIZE);
+	fill_memblock();
 }
 
 void dummy_physical_memory_init(void)
 {
 	memory_block.base = malloc(MEM_SIZE);
 	assert(memory_block.base);
+	fill_memblock();
 }
 
 void dummy_physical_memory_cleanup(void)
diff --git a/tools/testing/memblock/tests/common.h b/tools/testing/memblock/tests/common.h
index d396e5423a8e..7a16a7dc8f2c 100644
--- a/tools/testing/memblock/tests/common.h
+++ b/tools/testing/memblock/tests/common.h
@@ -51,6 +51,18 @@
 	assert((_expected) < (_seen)); \
 } while (0)
 
+/**
+ * ASSERT_MEM_EQ():
+ * Check that the first @_size bytes of @_seen are all equal to @_expected.
+ * If false, print failed test message (if running with --verbose) and then
+ * assert.
+ */
+#define ASSERT_MEM_EQ(_seen, _expected, _size) do { \
+	for (int _i = 0; _i < (_size); _i++) { \
+		ASSERT_EQ((_seen)[_i], (_expected)); \
+	} \
+} while (0)
+
 #define PREFIX_PUSH() prefix_push(__func__)
 
 /*
@@ -70,6 +82,7 @@ struct region {
 
 void reset_memblock_regions(void);
 void reset_memblock_attributes(void);
+void fill_memblock(void);
 void setup_memblock(void);
 void dummy_physical_memory_init(void);
 void dummy_physical_memory_cleanup(void);
