Kconfig: select whether to use a mem pool or kmalloc

Not automatically tied into the default global allocator yet.

Author: tylerwhall

Kconfig

@@ -4,3 +4,44 @@ menuconfig RUST
 	select CPLUSPLUS
 	help
 	  Rust language support.
+
+if RUST
+choice RUST_GLOBAL_ALLOCATOR
+	prompt "Rust global allocator"
+	default RUST_ALLOC_POOL
+	help
+	  The global allocator can either use k_malloc or a dedicated sys mem
+	  pool for Rust allocations. A dedicated pool is required for userspace
+	  because the pool must be placed in a shared memory region accessible
+	  to all Rust userspace threads.
+
+config RUST_ALLOC_KMALLOC
+	bool "k_malloc"
+	depends on !USERSPACE
+	help
+	  Adjust the pool size with CONFIG_HEAP_MEM_POOL_SIZE. Must be non-zero.
+
+config RUST_ALLOC_POOL
+	bool "Dedicated memory pool"
+	help
+	  Required for userspace.
+endchoice
+
+if RUST_ALLOC_POOL
+config RUST_HEAP_MEM_POOL_SIZE
+	int "Rust heap memory pool size (in bytes)"
+	default 1024
+	help
+	  This option specifies the size of the heap memory pool created
+	  specifically to act as the Rust global allocator.  Must be a power of
+	  2. A size of zero means that no heap memory pool is defined.
+
+config RUST_HEAP_MEM_POOL_MIN_SIZE
+	int "The smallest blocks in the Rust heap memory pool (in bytes)"
+	default 16
+	help
+	  This option specifies the size of the smallest block in the pool.
+	  Option must be a power of 2 and lower than or equal to the size
+	  of the entire pool.
+endif
+endif

rust-smem.c

@@ -1,9 +1,3 @@
-/*
- * Copyright (c) 2012-2014 Wind River Systems, Inc.
- *
- * SPDX-License-Identifier: Apache-2.0
- */
-
 #include <zephyr.h>
 #include <init.h>
 #include <misc/mempool.h>
@@ -18,10 +12,14 @@ K_APPMEM_PARTITION_DEFINE(rust_std_partition);
 #define RUST_STD_SECTION .data
 #endif
 
-#define RUST_STD_MEM_POOL_SIZE 1024
-SYS_MEM_POOL_DEFINE(rust_std_mem_pool, NULL, 16,
-                    RUST_STD_MEM_POOL_SIZE, 1, 4, RUST_STD_SECTION);
+#if defined(CONFIG_RUST_ALLOC_POOL)
+SYS_MEM_POOL_DEFINE(rust_std_mem_pool, NULL, CONFIG_RUST_HEAP_MEM_POOL_MIN_SIZE,
+                    CONFIG_RUST_HEAP_MEM_POOL_SIZE, 1, 4, RUST_STD_SECTION);
+#elif CONFIG_HEAP_MEM_POOL_SIZE == 0
+#error CONFIG_HEAP_MEM_POOL_SIZE (k_malloc) must be non-zero if not using a Rust sys mem pool.
+#endif
 
+#if defined(CONFIG_USERSPACE) || defined(CONFIG_RUST_ALLOC_POOL)
 static int rust_std_init(struct device *arg)
 {
     ARG_UNUSED(arg);
@@ -30,9 +28,12 @@ static int rust_std_init(struct device *arg)
     k_mem_domain_init(&rust_std_domain, 0, NULL);
     k_mem_domain_add_partition(&rust_std_domain, &rust_std_partition);
 #endif
+#ifdef CONFIG_RUST_ALLOC_POOL
     sys_mem_pool_init(&rust_std_mem_pool);
+#endif
 
     return 0;
 }
 
 SYS_INIT(rust_std_init, PRE_KERNEL_2, CONFIG_APPLICATION_INIT_PRIORITY);
+#endif

samples/rust-app/prj.conf

@@ -1,4 +1,5 @@
 CONFIG_RUST=y
+CONFIG_RUST_ALLOC_POOL=y
 CONFIG_SERIAL=y
 CONFIG_UART_NATIVE_POSIX=y
 CONFIG_NATIVE_UART_0_ON_OWN_PTY=y