llext: fix overlap checks for aligned regions

The overlap checks in the section mapping code were not taking into
account the alignment padding added to the start of each region, which
could lead to false positives when checking for overlaps.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>

subsys/llext/llext_load.c

@@ -301,9 +301,12 @@ static int llext_map_sections(struct llext_loader *ldr, struct llext *ext,
 
 		if (region->sh_type == SHT_NULL) {
 			/* First section of this type, copy all info to the
-			 * region descriptor.
+			 * region descriptor. Clear the 'sh_info' field so
+			 * it holds the number of bytes added at the start of
+			 * the region for alignment corrections.
 			 */
 			memcpy(region, shdr, sizeof(*region));
+			region->sh_info = 0;
 		} else {
 			/* Make sure this section is compatible with the region */
 			if ((shdr->sh_flags & SHF_BASIC_TYPE_MASK) !=
@@ -384,6 +387,7 @@ static int llext_map_sections(struct llext_loader *ldr, struct llext *ext,
 					}
 					region->sh_offset -= rest;
 					region->sh_size += rest;
+					region->sh_info += rest;
 				}
 				region->sh_addralign = shdr->sh_addralign;
 			}
@@ -428,7 +432,7 @@ static int llext_map_sections(struct llext_loader *ldr, struct llext *ext,
 				/*
 				 * Test regions that have VMA ranges for overlaps
 				 */
-#define BOT(reg) reg->sh_addr
+#define BOT(reg) (reg->sh_addr + reg->sh_info)
 #define TOP(reg) (reg->sh_addr + reg->sh_size - 1)
 				if ((BOT(x) <= BOT(y) && TOP(x) >= BOT(y)) ||
 				    (BOT(y) <= BOT(x) && TOP(y) >= BOT(x))) {
@@ -451,7 +455,7 @@ static int llext_map_sections(struct llext_loader *ldr, struct llext *ext,
 				continue;
 			}
 
-#define BOT(reg) reg->sh_offset
+#define BOT(reg) (reg->sh_offset + reg->sh_info)
 #define TOP(reg) (reg->sh_offset + reg->sh_size - 1)
 			if ((BOT(x) <= BOT(y) && TOP(x) >= BOT(y)) ||
 			    (BOT(y) <= BOT(x) && TOP(y) >= BOT(x))) {