core/init: Don't checksum MPIPL data areas

Right now the romem checksum runs from _start until the start of our
data area. This spans the area used for the MPIPL data structures since
they're included in the SPIRA-H data area.

Reviewed-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

core/init.c

@@ -927,8 +927,12 @@ static void checksum_romem(void)
 	if (chip_quirk(QUIRK_SLOW_SIM))
 		return;
 
-	csum = mem_csum(_start, _romem_end);
+	csum = mem_csum(_start, _head_end);
 	romem_csum ^= csum;
+
+	csum = mem_csum(_stext, _romem_end);
+	romem_csum ^= csum;
+
 	csum = mem_csum(__builtin_kernel_start, __builtin_kernel_end);
 	romem_csum ^= csum;
 }

include/skiboot.h

@@ -37,6 +37,7 @@ extern struct mem_region *mem_region_next(struct mem_region *region);
 
 /* Misc linker script symbols */
 extern char _start[];
+extern char _head_end[];
 extern char _stext[];
 extern char _etext[];
 extern char __sym_map_end[];

skiboot.lds.S

@@ -69,6 +69,13 @@ SECTIONS
 		KEEP(*(.spirah.data))
 	}
 
+	_head_end = .;
+
+	/*
+	 * The following sections are read-write at runtime. We need
+	 * to skip over them when checksumming the skiboot images
+	 * before a fast-reboot.
+	 */
 	. = PROC_DUMP_AREA_OFF;
 	.procdump : {
 		KEEP(*(.procdump.data))
@@ -94,6 +101,8 @@ SECTIONS
 		KEEP(*(.cpuctrl.data))
 	}
 
+	/* ...and back to RO */
+
 	. = ALIGN(0x10);
 	_stext = .;
  	.text : {