[PATCH] Implement ALTERNATE memory layout.

[Krzysztof Halasa]

Signed-off-by: Krzysztof Hałasa <khc at pm.waw.pl>

--- a/arch/arm/cpu/start.c
+++ b/arch/arm/cpu/start.c
@@ -58,7 +58,6 @@ static noinline __noreturn void __start(uint32_t membase, uint32_t memsize,
 	endmem -= STACK_SIZE; /* Stack */
 
 	if (IS_ENABLED(CONFIG_MMU_EARLY)) {
-
 		endmem &= ~0x3fff;
 		endmem -= SZ_16K; /* ttb */
 
@@ -66,6 +65,9 @@ static noinline __noreturn void __start(uint32_t membase, uint32_t memsize,
 			mmu_early_enable(membase, memsize, endmem);
 	}
 
+#ifdef CONFIG_MEMORY_LAYOUT_ALTERNATE
+		malloc_end = endmem;
+#else
 	if ((unsigned long)_text > membase + memsize ||
 			(unsigned long)_text < membase)
 		/*
@@ -76,15 +78,21 @@ static noinline __noreturn void __start(uint32_t membase, uint32_t memsize,
 		malloc_end = endmem;
 	else
 		malloc_end = (unsigned long)_text;
+#endif
 
 	/*
 	 * Maximum malloc space is the Kconfig value if given
 	 * or 64MB.
 	 */
 	if (MALLOC_SIZE > 0) {
-		malloc_start = malloc_end - MALLOC_SIZE;
-		if (malloc_start < membase)
+		if (malloc_end > membase + MALLOC_SIZE)
+			malloc_start = malloc_end - MALLOC_SIZE;
+		else
 			malloc_start = membase;
+		if (malloc_start < (unsigned long)_end &&
+		    malloc_end > (unsigned long)_text)
+			/* malloc area follows text */
+			malloc_start = (unsigned long)_end;
 	} else {
 		malloc_start = malloc_end - (malloc_end - membase) / 2;
 		if (malloc_end - malloc_start > SZ_64M)
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -161,7 +161,7 @@ choice
 config MEMORY_LAYOUT_DEFAULT
 	bool "use default memory layout"
 	help
-	  select this option to use bareboxs standard memory layout:
+	  select this option to use barebox's standard memory layout:
 
 	  stack
 	  -----
@@ -169,6 +169,17 @@ config MEMORY_LAYOUT_DEFAULT
 	  -----
 	  TEXT_BASE
 
+config MEMORY_LAYOUT_ALTERNATE
+	bool "use alternate memory layout"
+	help
+	  select this option to use barebox's alternate memory layout:
+
+	  TEXT_BASE
+	  -----
+	  malloc heap
+	  -----
+	  stack
+
 config MEMORY_LAYOUT_FIXED
 	bool "manually assign a memory layout"
 	help