Changeset da13982 in mainline for kernel/meson.build

Timestamp:

2023-10-26T15:20:07Z (15 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

master, topic/msim-upgrade, topic/simplify-dev-export

Children:

2fbb42f

Parents:

d28bdbe

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-10-26 14:42:03)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2023-10-26 15:20:07)

Message:

Read symbol table from ELF sections

Instead of the currently broken data generated using genmap.py,
read the ELF symbol table for stack traces and symbol names.
In addition to that, prepare ground for accessing DWARF debug
sections.

Because neither .symtab, nor .debug_* sections are
normally part of the program image, these have to be provided
externally. Instead of the previous way of relinking kernel
to bake in the symbol data, we now only link kernel once
and the extra debug data is loaded as part of the initrd image.

File:

• kernel/meson.build (modified) (3 diffs)

kernel/meson.build

@@ -41 +41 @@
 # Defines test_src
 subdir('test')
-
-## Cross-platform assembly to start a symtab.data section
-#
-symtab_section = '.section symtab.data, "a", ' + atsign + 'progbits;'
 
 kernel_include_dirs = include_directories(
@@ -97 +93 @@
 endif
 
-if CONFIG_STRIP_BINARIES
-        # TODO: do this after disassembling
-        kernel_link_args += [ '-s' ]
-endif
-
 kernel_c_args = arch_kernel_c_args + kernel_defs + [
         '-ffreestanding',
@@ -149 +140 @@
 all_kernel_objects = [ instrumentables, noninstrumentables ]
 
-# We iterate the build several times to get symbol table right.
-# Three times is sufficient to get correct even symbols after symtab.
+kernel_name = 'kernel.elf'
+kernel_map_name = kernel_name + '.map'
+kernel_map_path = meson.current_build_dir() / kernel_map_name
+
+kernel_elf = executable(kernel_name,
+        include_directories: kernel_include_dirs,
+        implicit_include_directories: false,
+        c_args: kernel_c_args,
+        link_args: kernel_c_args + kernel_link_args + [
+                '-Wl,-Map,' + kernel_map_path,
+        ],
+        link_depends: kernel_ldscript,
+        link_whole: all_kernel_objects,
+        pie: false,
+)
+
+kernel_dbg = custom_target('kernel.dbg',
+        output: 'kernel.dbg',
+        input: kernel_elf,
+        command: [
+                objcopy,
+                '--only-keep-debug',
+                '@INPUT@',
+                '@OUTPUT@',
+        ],
+)
+
+kernel_elf_stripped = custom_target(kernel_name + '.stripped',
+        output: kernel_name + '.stripped',
+        input: kernel_elf,
+        command: [
+                objcopy,
+                '--strip-unneeded',
+                '@INPUT@',
+                '@OUTPUT@',
+        ],
+)
+
+rd_init_binaries += [[ kernel_elf_stripped, 'boot/kernel.elf' ]]
+install_files += [[ 'boot', kernel_elf_stripped.full_path(), 'kernel.elf' ]]
+install_deps += [ kernel_elf_stripped ]
 
 if CONFIG_SYMTAB
-        # Iterate build three times.
-        iterations = [ 1, 2, 3 ]
-
-        # Generates symbol table information as an object file.
-        genmap = find_program('tools/genmap.py')
-
-        # Symbol table dump needed for genmap.
-        kernel_syms = custom_target('kernel_syms.txt',
-                input: all_kernel_objects,
-                output: 'kernel_syms.txt',
-                command: [ objdump, '-t', '@INPUT@' ],
-                capture: true,
-        )
-else
-        # Build just once.
-        iterations = [ 1 ]
-endif
-
-# Empty symbol map for first iteration.
-kernel_map_S = custom_target('empty_map.S',
-        output: 'empty_map.S',
-        capture: true,
-        command: [ 'echo', kernel_as_prolog + symtab_section ],
-)
-
-foreach iter : iterations
-        is_last = (iter == iterations.length())
-        kernel_name = 'kernel.@0@.elf'.format(iter)
-        kernel_map_name = kernel_name + '.map'
-        kernel_map_path = meson.current_build_dir() / kernel_map_name
-
-        kernel_elf = executable(kernel_name, kernel_map_S,
-                include_directories: kernel_include_dirs,
-                implicit_include_directories: false,
-                c_args: kernel_c_args,
-                link_args: kernel_c_args + kernel_link_args + [
-                        '-Wl,-Map,' + kernel_map_path,
-                ],
-                link_depends: kernel_ldscript,
-                link_whole: all_kernel_objects,
-                pie: false,
-        )
-
-        # Generate symbol table if this is not the final iteration.
-        if not is_last
-
-                # TODO: Teach kernel to read its own ELF symbol table and get rid of this nonsense.
-                # Need to first make sure all architectures (even future ones with dumb bootloaders) can use ELF formatted kernel.
-
-                kernel_map_bin = custom_target(kernel_map_name + '.bin',
-                        output: kernel_map_name + '.bin',
-                        input: [ kernel_elf, kernel_syms ],
-                        command: [ genmap, kernel_map_path, '@INPUT1@', '@OUTPUT@' ],
-                )
-
-                kernel_map_S_name = kernel_name + '.map.S'
-
-                kernel_map_S = custom_target(kernel_map_S_name,
-                        input: kernel_map_bin,
-                        output: kernel_map_S_name,
-                        capture: true,
-                        command: [ 'echo', kernel_as_prolog + symtab_section + ' .incbin "@INPUT@"' ],
-                )
-        endif
-endforeach
-
-rd_init_binaries += [[ kernel_elf, 'boot/kernel.elf' ]]
-
-install_files += [[ 'boot', kernel_elf.full_path(), 'kernel.elf' ]]
-install_deps += [ kernel_elf ]
+        rd_init_binaries += [[ kernel_dbg, 'kernel.dbg' ]]
+        install_files += [[ 'boot', kernel_dbg.full_path(), 'kernel.dbg' ]]
+        install_deps += [ kernel_dbg ]
+endif
 
 kernel_disasm = custom_target('kernel.elf.disasm',