lib/os/heap: introduce option to force big heap mode

This option allows forcing big heap mode. Useful on for getting 8-byte
aligned blocks on 32-bit machines.

Signed-off-by: Martin Åberg <[email protected]>

Author: tbr-tt

arch/sparc/Kconfig

@@ -13,6 +13,10 @@ config SPARC_NWIN
 	help
 	  Number of implemented register windows.
 
+# ISA requires 8-byte alignment for 64-bit data access
+config SYS_HEAP_ALWAYS_BIG_MODE
+	default y
+
 config GEN_ISR_TABLES
 	default y
 

lib/os/Kconfig

@@ -46,6 +46,16 @@ config SYS_HEAP_ALLOC_LOOPS
 	  keeps the maximum runtime at a tight bound so that the heap
 	  is useful in locked or ISR contexts.
 
+config SYS_HEAP_ALWAYS_BIG_MODE
+	bool "Always use the heap big chunks mode"
+	help
+	  The sys_heap allocator by default returns pointers to blocks
+	  which are guaranteed to be aligned to the pointer size.
+	  By enabling the "big chunks" mode, the returned blocks are
+	  guaranteed to be 8 byte aligned, also on 32-bit platforms.
+	  If this option is enabled, the "big chunks" mode will always
+	  be used by sys_heap.
+
 config PRINTK64
 	bool "Enable 64 bit printk conversions (DEPRECATED)"
 	help

lib/os/heap.h

@@ -66,6 +66,9 @@ struct z_heap {
 
 static inline bool big_heap_chunks(size_t chunks)
 {
+	if (IS_ENABLED(CONFIG_SYS_HEAP_ALWAYS_BIG_MODE)) {
+		return 1;
+	}
 	return sizeof(void *) > 4U || chunks > 0x7fffU;
 }