llext: fix alignment of cold / detached sections

Cold sections within LLEXT modules should be page-size aligned to
allow setting permission flags. They're never copied after being
initially placed in DRAM, so alignment should happen already in ELF
files.

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

Author: lyakh

scripts/llext_link_helper.py

@@ -26,6 +26,10 @@ def parse_args():
 	parser.add_argument('params', nargs='+', help='Additional linker parameters')
 	parser.add_argument("-f", "--file", required=True, type=str,
 						help='Object file name')
+	parser.add_argument("-c", "--copy", required=True, type=str,
+						help='Objcopy command')
+	parser.add_argument("-o", "--output", required=True, type=str,
+						help='Output file name')
 	parser.add_argument("-t", "--text-addr", required=True, type=str,
 						help='.text section address')
 	parser.add_argument("-s", "--size-file", required=True, type=str,
@@ -148,11 +152,16 @@ def main():
 	# we accept only the .coldrodata name for now.
 
 	dram_addr = 0
+	first_dram_text = None
+	first_dram_rodata = None
 
 	for section in executable:
 		s_alignment = section.header['sh_addralign']
 		s_name = section.name
 
+		if not first_dram_text:
+			first_dram_text = s_name
+
 		dram_addr = align_up(dram_addr, s_alignment)
 
 		command.append(f'-Wl,--section-start={s_name}=0x{dram_addr:x}')
@@ -163,6 +172,9 @@ def main():
 		s_alignment = section.header['sh_addralign']
 		s_name = section.name
 
+		if not first_dram_rodata:
+			first_dram_rodata = s_name
+
 		dram_addr = align_up(dram_addr, s_alignment)
 
 		command.append(f'-Wl,--section-start={s_name}=0x{dram_addr:x}')
@@ -196,9 +208,20 @@ def main():
 
 		start_addr += section.header['sh_size']
 
+	command.extend(['-o', f'{args.file}.tmp'])
 	command.extend(args.params)
 
 	subprocess.run(command)
 
+	copy_command = [args.copy]
+
+	if first_dram_text:
+		copy_command.extend(['--set-section-alignment', f'{first_dram_text}=4096'])
+	if first_dram_rodata:
+		copy_command.extend(['--set-section-alignment', f'{first_dram_rodata}=4096'])
+
+	copy_command.extend([f'{args.file}.tmp', f'{args.output}'])
+	subprocess.run(copy_command)
+
 if __name__ == "__main__":
 	main()

zephyr/CMakeLists.txt

@@ -107,9 +107,9 @@ function(sof_llext_build module)
 		POST_BUILD
 		COMMAND ${PYTHON_EXECUTABLE} ${SOF_BASE}scripts/llext_link_helper.py -s ${size_file}
 			--text-addr=${CONFIG_LIBRARY_BASE_ADDRESS}
-			-f ${proc_in_file} ${CMAKE_C_COMPILER} --
-			-o ${proc_out_file} ${EXTRA_LINKER_PARAMS}
-	                $<TARGET_OBJECTS:${module}_llext_lib>
+			-c $<TARGET_PROPERTY:bintools,elfconvert_command>
+			-f ${proc_in_file} -o ${proc_out_file} ${CMAKE_C_COMPILER} --
+			${EXTRA_LINKER_PARAMS} $<TARGET_OBJECTS:${module}_llext_lib>
 	)
 
 	add_llext_command(TARGET ${module}