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authorKris Van Hees2024-09-06 10:45:03 -0400
committerMasahiro Yamada2024-09-20 09:21:43 +0900
commit5f5e7344322f0b0676579af054c787ed57d1c1df (patch)
treea710ed67fec6d10433b8aac97dd4e52d421b1460 /Documentation/process
parent23d93aa4b3b90b6e3dc8e6b6bb36580c1068bc07 (diff)
kbuild: generate offset range data for builtin modules
Create file module.builtin.ranges that can be used to find where built-in modules are located by their addresses. This will be useful for tracing tools to find what functions are for various built-in modules. The offset range data for builtin modules is generated using: - modules.builtin: associates object files with module names - vmlinux.map: provides load order of sections and offset of first member per section - vmlinux.o.map: provides offset of object file content per section - .*.cmd: build cmd file with KBUILD_MODFILE The generated data will look like: .text 00000000-00000000 = _text .text 0000baf0-0000cb10 amd_uncore .text 0009bd10-0009c8e0 iosf_mbi ... .text 00b9f080-00ba011a intel_skl_int3472_discrete .text 00ba0120-00ba03c0 intel_skl_int3472_discrete intel_skl_int3472_tps68470 .text 00ba03c0-00ba08d6 intel_skl_int3472_tps68470 ... .data 00000000-00000000 = _sdata .data 0000f020-0000f680 amd_uncore For each ELF section, it lists the offset of the first symbol. This can be used to determine the base address of the section at runtime. Next, it lists (in strict ascending order) offset ranges in that section that cover the symbols of one or more builtin modules. Multiple ranges can apply to a single module, and ranges can be shared between modules. The CONFIG_BUILTIN_MODULE_RANGES option controls whether offset range data is generated for kernel modules that are built into the kernel image. How it works: 1. The modules.builtin file is parsed to obtain a list of built-in module names and their associated object names (the .ko file that the module would be in if it were a loadable module, hereafter referred to as <kmodfile>). This object name can be used to identify objects in the kernel compile because any C or assembler code that ends up into a built-in module will have the option -DKBUILD_MODFILE=<kmodfile> present in its build command, and those can be found in the .<obj>.cmd file in the kernel build tree. If an object is part of multiple modules, they will all be listed in the KBUILD_MODFILE option argument. This allows us to conclusively determine whether an object in the kernel build belong to any modules, and which. 2. The vmlinux.map is parsed next to determine the base address of each top level section so that all addresses into the section can be turned into offsets. This makes it possible to handle sections getting loaded at different addresses at system boot. We also determine an 'anchor' symbol at the beginning of each section to make it possible to calculate the true base address of a section at runtime (i.e. symbol address - symbol offset). We collect start addresses of sections that are included in the top level section. This is used when vmlinux is linked using vmlinux.o, because in that case, we need to look at the vmlinux.o linker map to know what object a symbol is found in. And finally, we process each symbol that is listed in vmlinux.map (or vmlinux.o.map) based on the following structure: vmlinux linked from vmlinux.a: vmlinux.map: <top level section> <included section> -- might be same as top level section) <object> -- built-in association known <symbol> -- belongs to module(s) object belongs to ... vmlinux linked from vmlinux.o: vmlinux.map: <top level section> <included section> -- might be same as top level section) vmlinux.o -- need to use vmlinux.o.map <symbol> -- ignored ... vmlinux.o.map: <section> <object> -- built-in association known <symbol> -- belongs to module(s) object belongs to ... 3. As sections, objects, and symbols are processed, offset ranges are constructed in a straight-forward way: - If the symbol belongs to one or more built-in modules: - If we were working on the same module(s), extend the range to include this object - If we were working on another module(s), close that range, and start the new one - If the symbol does not belong to any built-in modules: - If we were working on a module(s) range, close that range Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com> Reviewed-by: Nick Alcock <nick.alcock@oracle.com> Reviewed-by: Alan Maguire <alan.maguire@oracle.com> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Tested-by: Sam James <sam@gentoo.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Sami Tolvanen <samitolvanen@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'Documentation/process')
-rw-r--r--Documentation/process/changes.rst7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index 3fc63f27c226..00f1ed7c59c3 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -64,6 +64,7 @@ GNU tar 1.28 tar --version
gtags (optional) 6.6.5 gtags --version
mkimage (optional) 2017.01 mkimage --version
Python (optional) 3.5.x python3 --version
+GNU AWK (optional) 5.1.0 gawk --version
====================== =============== ========================================
.. [#f1] Sphinx is needed only to build the Kernel documentation
@@ -192,6 +193,12 @@ platforms. The tool is available via the ``u-boot-tools`` package or can be
built from the U-Boot source code. See the instructions at
https://docs.u-boot.org/en/latest/build/tools.html#building-tools-for-linux
+GNU AWK
+-------
+
+GNU AWK is needed if you want kernel builds to generate address range data for
+builtin modules (CONFIG_BUILTIN_MODULE_RANGES).
+
System utilities
****************