Working Directory Estimation

[augelu-tng]

The cmd files in the output tree often include relative paths. It is typically unclear to which working directory these paths are relative to.
At the moment the _get_working_directory function estimates the working directory by trial and error of different options.

Is there a better solution for this?
Maybe we could add a new working directory field in cmd files or the paths in cmd files could be standardized to all use the same working directory?

[augelu-tng]

Working Directory Examples for Cmd Files

cmd_file_working_directory_examples.tar.gz contains example cmd files in order to demonstrate the inconsistent usage of relative paths in cmd files.

When building the cmd graph starting from vmlinux we generally encounter two scenarios:

1. Paths relative to the cmd file, e.g.,
   • linux/kernel_build/kernel/sched/.built-in.a.cmd includes relative path core.o pointing to linux/kernel_build/kernel/sched/core.o
2. Paths relative to the output tree linux/kernel_build, e.g.,
   • linux/kernel_build/kernel/.resource.o.cmd includes relative path ../kernel/resource.c pointing to linux/kernel/resource.c.
   • linux/kernel_build/arch/x86/include/generated/uapi/asm/.unistd_32.h.cmd includes relative path ../arch/x86/entry/syscalls/syscall_32.tbl pointing to linux/arch/x86/entry/syscalls/syscall_32.tbl
   • linux/kernel_build/lib/.lib.a.cmd includes relative path lib/argv_split.o pointing to linux/kernel_build/lib/argv_split.o (same for linux/kernel_build/arch/x86/lib/.lib.a.cmd)

Conclusion:
In most cmd files the output tree is the working directory.
The exception are archive cmd files *.a.cmd which include paths relative to the cmd files themselves.
The exception to the exception are linux/kernel_build/lib/.lib.a.cmd and linux/kernel_build/arch/x86/lib/lib.a which again include paths relative to the output tree.

Cmd Files outside of vmlinux tree
When also considering cmd files that are not reached from vmlinux more inconsistencies show up:

1. Paths relative to linux/tools/objtool, e.g.,
   • linux/kernel_build/tools/objtool/arch/x86/.special.o.cmd includes relative path arch/x86/special.c pointing to linux/tools/objtool/arch/x86/special.c
2. Paths relative to linux/tools/lib/subcmd, e.g.,
   • linux/kernel_build/tools/objtool/libsubcmd/.sigchain.o.cmd includes relative path sigchain.c pointing to linux/tools/lib/subcmd/sigchain.c

Examples were taken from linux.v6.17.tinyconfig.tar.gz and linux.v6.17.defconfig.tar.gz.