layout: Add explict .stack section

This replaces our hacky asserts and makes debugging easier.

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

layout.ld

@@ -9,8 +9,6 @@ PHDRS
 /* Loaders like to put stuff in low memory (< 1M), so we don't use it. */
 ram_min = 1M;
 ram_max = 2M;
-/* Our stack grows down from ram_max. TODO: Add a guard for stack overflows. */
-stack_size = 64K;
 
 SECTIONS
 {
@@ -28,16 +26,17 @@ SECTIONS
 	.data   : { *(.data .data.*)     }
 	data_size = . - data_start;
 
-	/* The BSS section isn't mapped from any file data. It is simply zeroed
-	   in RAM. So our file size should be computed from here.                 */
-	file_size = . - ram_min;
+	/* The BSS section isn't mapped from file data. It is just zeroed in RAM. */
 	.bss : {
 		bss_start = .;
 		*(.bss .bss.*)
 		bss_size = . - bss_start;
 	}
 
-	ASSERT((. <= ram_max - stack_size), "firmware size too big for RAM region")
+	/* Our stack grows down from ram_max. TODO: Add stack overflow guards.    */
+	stack_size = 64K;
+	. = ram_max - stack_size;
+	.stack (NOLOAD) : { . += stack_size; } :NONE
 
 	/* Match edk2's GccBase.lds DISCARD section */
 	/DISCARD/ : {