lib: libc: common: Add malloc heap stats support

Add support for retrieving heap stats for the malloc heap in the common
libc malloc implementation. This provides the ability to see free and
used bytes using the same structure as the kernel heap.
Without this there is no method to retrieve the malloc heap usage as the
relevant sys_heap structure is private.

Signed-off-by: Graham Roff <grahamr@qti.qualcomm.com>

Author: grahamroff-dev

lib/libc/common/include/sys_malloc.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ *
+ * @brief Zephyr common libc malloc extensions
+ */
+
+#ifndef ZEPHYR_LIB_LIBC_COMMON_INCLUDE_SYS_MALLOC_H_
+#define ZEPHYR_LIB_LIBC_COMMON_INCLUDE_SYS_MALLOC_H_
+
+#include <zephyr/sys/sys_heap.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Get the runtime statistics of the malloc heap
+ *
+ * @kconfig_dep{CONFIG_SYS_HEAP_RUNTIME_STATS}
+ *
+ * @param stats Pointer to struct to copy statistics into
+ * @return -EINVAL if null pointers, otherwise 0
+ */
+int malloc_runtime_stats_get(struct sys_memory_stats *stats);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* ZEPHYR_LIB_LIBC_COMMON_INCLUDE_SYS_MALLOC_H_ */

lib/libc/common/source/stdlib/malloc.c

@@ -262,6 +262,23 @@ void free(void *ptr)
 	malloc_unlock();
 }
 
+#ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
+
+int malloc_runtime_stats_get(struct sys_memory_stats *stats)
+{
+	int ret;
+
+	malloc_lock();
+
+	ret = sys_heap_runtime_stats_get(&z_malloc_heap, stats);
+
+	malloc_unlock();
+
+	return ret;
+}
+
+#endif /* CONFIG_SYS_HEAP_RUNTIME_STATS */
+
 SYS_INIT(malloc_prepare, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_LIBC);
 #else /* No malloc arena */
 void *malloc(size_t size)

tests/lib/c_lib/common/prj.conf

@@ -4,3 +4,4 @@ CONFIG_ZTEST_FATAL_HOOK=y
 CONFIG_MINIMAL_LIBC_NON_REENTRANT_FUNCTIONS=y
 CONFIG_MINIMAL_LIBC_RAND=y
 CONFIG_POSIX_C_LANG_SUPPORT_R=y
+CONFIG_SYS_HEAP_RUNTIME_STATS=y

tests/lib/c_lib/common/src/main.c

@@ -43,6 +43,9 @@
 #ifdef CONFIG_NEWLIB_LIBC
 #include <unistd.h>
 #endif
+#ifdef CONFIG_COMMON_LIBC_MALLOC
+#include <sys_malloc.h>
+#endif
 
 #define STACK_SIZE (512 + CONFIG_TEST_EXTRA_STACK_SIZE)
 #define LIST_LEN 2
@@ -1313,6 +1316,47 @@ ZTEST(libc_common, test_exit)
 	zassert_equal(a, 0, "exit failed");
 #endif
 }
+
+/**
+ *
+ * @brief Test malloc and associated functions.
+ *
+ */
+ZTEST(libc_common, test_malloc)
+{
+#if defined(CONFIG_COMMON_LIBC_MALLOC) && CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE > 220
+	char *buf = NULL, *temp_buf = NULL;
+#ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
+	int rc;
+	struct sys_memory_stats pre_malloc_stats, post_malloc_stats;
+
+	rc = malloc_runtime_stats_get(&pre_malloc_stats);
+	zassert_equal(rc, 0, "malloc_runtime_stats_get_failed: %d", rc);
+#endif
+
+	buf = malloc(100);
+	zassert_not_null(buf, "malloc failed");
+
+#ifdef CONFIG_SYS_HEAP_RUNTIME_STATS
+	rc = malloc_runtime_stats_get(&post_malloc_stats);
+	zassert_equal(rc, 0, "malloc_runtime_stats_get_failed: %d", rc);
+	zassert(pre_malloc_stats.free_bytes - post_malloc_stats.free_bytes >= 100,
+		"malloc_runtime_stats_get failed, free bytes did not reduce as expected");
+	zassert(post_malloc_stats.allocated_bytes - pre_malloc_stats.allocated_bytes >= 100,
+		"malloc_runtime_stats_get failed, used bytes did not increase as expected");
+#endif
+
+	temp_buf = realloc(buf, 200);
+	zassert_not_null(temp_buf, "realloc failed");
+	if (temp_buf != NULL) {
+		buf = temp_buf;
+	}
+
+	free(buf);
+#else
+	ztest_test_skip();
+#endif /* CONFIG_COMMON_LIBC_MALLOC && CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE > 220 */
+}
 /**
  * @}
  */