llext: add support for executable sections in IMR / DRAM

Make the link helper collect any non-default executable sections and
link them at 0 to be relocated at run-time to IMR / DRAM addresses.
Also tell Zephyr to treat any such sections as detached.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

scripts/llext_link_helper.py

@@ -73,9 +73,12 @@ def main():
 
 	command = [args.command]
 
+	executable = []
 	writable = []
 	readonly = []
 
+	text_found = False
+
 	elf = ELFFile(open(args.file, 'rb'))
 
 	# Create an object file with sections grouped by their properties,
@@ -102,13 +105,14 @@ def main():
 			# In general additional executable sections are possible, e.g.
 			# .init. In the future support for arbitrary such sections can be
 			# added, similar to writable and read-only data below.
-			if s_name != '.text':
-				print(f"Warning! Non-standard executable section {s_name}")
-
-			text_addr = max_alignment(text_addr, 0x1000, s_alignment)
-			text_size = s_size
-
-			command.append(f'-Wl,-Ttext=0x{text_addr:x}')
+			if s_name == '.text':
+				text_found = True
+				text_addr = max_alignment(text_addr, 0x1000, s_alignment)
+				text_size = s_size
+				command.append(f'-Wl,-Ttext=0x{text_addr:x}')
+			else:
+				# Any additional executable sections are intended for IMR
+				executable.append(section)
 
 			continue
 
@@ -122,6 +126,24 @@ def main():
 			# .rodata or other read-only sections
 			readonly.append(section)
 
+	if not text_found:
+		raise RuntimeError('No .text section found in the object file')
+
+	# IMR sections don't need to be linked with SRAM addresses
+	imr_addr = 0
+
+	for section in executable:
+		s_alignment = section.header['sh_addralign']
+		s_name = section.name
+
+		imr_addr = align_up(imr_addr, s_alignment)
+
+		command.append(f'-Wl,--section-start={s_name}=0x{imr_addr:x}')
+
+		imr_addr += section.header['sh_size']
+
+	# So far there doesn't seem to be any reason to align additional
+	# executable sections after .text
 	start_addr = align_up(text_addr + text_size, 0x1000)
 
 	for section in readonly:

src/library_manager/llext_manager.c

@@ -219,6 +219,13 @@ static int llext_manager_unload_module(uint32_t module_id, const struct sof_man_
 	return err;
 }
 
+#define LLEXT_SECTION_MIN_ADDR 0x10000
+
+static bool llext_manager_section_detached(const elf_shdr_t *shdr)
+{
+	return shdr->sh_addr < LLEXT_SECTION_MIN_ADDR;
+}
+
 static int llext_manager_link(struct sof_man_fw_desc *desc, struct sof_man_module *mod,
 			      uint32_t module_id, struct module_data *md, const void **buildinfo,
 			      const struct sof_man_module_manifest **mod_manifest)
@@ -232,6 +239,7 @@ static int llext_manager_link(struct sof_man_fw_desc *desc, struct sof_man_modul
 	struct llext_load_param ldr_parm = {
 		.relocate_local = !ctx->segment[LIB_MANAGER_TEXT].size,
 		.pre_located = true,
+		.section_detached = llext_manager_section_detached,
 	};
 	int ret = llext_load(&ebl.loader, mod->name, &md->llext, &ldr_parm);