llext: add support for building relocatable modules

Add support for relocatable objects to the llext module build system.
In such builds no ELF segments are created, so we need to process all
sections individually.

Signed-off-by: Guennadi Liakhovetski <[email protected]>

scripts/llext_link_helper.py

@@ -7,9 +7,11 @@
 # portable way to do that. Therefore we pass the linker path and all the command
 # line parameters to this script and call the linker directly.
 
+import os
 import argparse
 import subprocess
 from elftools.elf.elffile import ELFFile
+import re
 
 args = None
 def parse_args():
@@ -33,21 +35,53 @@ def main():
 	elf = ELFFile(open(args.file, 'rb'))
 
 	text_addr = int(args.text_addr, 0)
+	p = re.compile('(^lib|\.so$)')
+	module = p.sub('', args.file)
 
-	text_offset = elf.get_section_by_name('.text').header.sh_offset
-	rodata_offset = elf.get_section_by_name('.rodata').header.sh_offset
-	data_offset = elf.get_section_by_name('.data').header.sh_offset
+	if elf.num_segments() != 0:
+		# A shared object type image, it contains segments
+		sections = ['.text', '.rodata', '.data', '.bss']
+		alignment = [0x1000, 0x1000, 0x10, 0x1000]
+	else:
+		# A relocatable object, need to handle all sections separately
+		sections = ['.text',
+			    f'._log_const.static.log_const_{module}_',
+			    '.static_uuids', '.z_init_APPLICATION90_0_', '.module',
+			    '.mod_buildinfo', '.data', '.trace_ctx', '.bss']
+		alignment = [0x1000, 0x1000, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, 0x1000]
 
-	upper = rodata_offset - text_offset + text_addr + 0xfff
-	rodata_addr = upper - (upper % 0x1000)
+	last_increment = 0
 
-	upper = data_offset - rodata_offset + rodata_addr + 0xf
-	data_addr = upper - (upper % 0x10)
+	command = [args.command]
+
+	for i in range(len(sections)):
+		try:
+			offset = elf.get_section_by_name(sections[i]).header.sh_offset
+			size = elf.get_section_by_name(sections[i]).header.sh_size
+		except:
+			continue
+
+		if last_increment == 0:
+			# first section must be .text and it must be successful
+			if i != 0 or sections[i] != '.text':
+                                break
+
+			addresse = text_addr
+		elif alignment[i] != 0:
+			upper = offset + last_increment + alignment[i] - 1
+			addresse = upper - (upper % alignment[i])
+		else:
+			addresse = offset + last_increment
+
+		last_increment = addresse - offset
+
+		if sections[i] == '.text':
+			command.append(f'-Wl,-Ttext=0x{text_addr:x}')
+		elif sections[i] == '.data':
+			command.append(f'-Wl,-Tdata=0x{addresse:x}')
+		else:
+			command.append(f'-Wl,--section-start={sections[i]}=0x{addresse:x}')
 
-	command = [args.command,
-		   f'-Wl,-Ttext=0x{text_addr:x}',
-		   f'-Wl,--section-start=.rodata=0x{rodata_addr:x}',
-		   f'-Wl,-Tdata=0x{data_addr:x}']
 	command.extend(args.params)
 
 	subprocess.run(command)