soc/intel/apl: Warn if CBFS is outside the memory mapped area

As part of the memory mapped BIOS region is covered by SRAM, check
that CBFS always fits the effectively mapped region of flash. This
is usually taken care of by reserving the SRAM range in the FMAP
(e.g. as BIOS_UNUSABLE), but can be missed.

Change-Id: If5a5b553ad4853723bf13349c809c4f6154aa5f2
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/30055
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/soc/intel/apollolake/mmap_boot.c

@@ -110,6 +110,8 @@ const struct region_device *boot_device_ro(void)
 
 static int iafw_boot_region_properties(struct cbfs_props *props)
 {
+	struct xlate_region_device *real_dev_ptr;
+	struct region *real_dev_reg;
 	struct region regn;
 
 	/* use fmap to locate CBFS area */
@@ -119,7 +121,19 @@ static int iafw_boot_region_properties(struct cbfs_props *props)
 	props->offset = region_offset(&regn);
 	props->size = region_sz(&regn);
 
-	printk(BIOS_DEBUG, "CBFS @ %zx size %zx\n", props->offset, props->size);
+	/* Check that we are within the memory mapped area. It's too
+	   easy to forget the SRAM mapping when crafting an FMAP file. */
+	real_dev_ptr = car_get_var_ptr(&real_dev);
+	real_dev_reg = &real_dev_ptr->sub_region;
+	if (region_is_subregion(real_dev_reg, &regn)) {
+		printk(BIOS_DEBUG, "CBFS @ %zx size %zx\n",
+		       props->offset, props->size);
+	} else {
+		printk(BIOS_CRIT,
+		       "ERROR: CBFS @ %zx size %zx exceeds mem-mapped area @ %zx size %zx\n",
+		       props->offset, props->size,
+		       region_offset(real_dev_reg), region_sz(real_dev_reg));
+	}
 
 	return 0;
 }