llvm-project

882d0251 - Improve the executable name detection in ELF core files. (#197341)

Improve the executable name detection in ELF core files. (#197341) A previous commit switched us to use the value of the AT_EXECFN, which is an entry in the aux vector, as the executable path. As it turns out, if a symlink is used to launch a program, the symlink path will be in the AT_EXECFN string in core file memory. The PRPSINFO also contains a basename of the program, and it will also be the symlink basename. The best source of information to figure out the executable name is from the NT_FILE note. This always has the resolved path to the executable. Now the executable name is found in a reliable way starting with finding the NT_FILE entry for the main executable. This can reliably be done by finding the NT_FILE entry whose address contains the AT_PHDR aux vector value. This value is the address of the program headers for the main executable. If there is no NT_FILE entry we can find, we fall back to the AT_EXECFN entry from memory and then fallback to the basename in the PRPSINFO. This patch also creates a placeholder as the main executable when the executable can't be found to ensure users can see which executable they will need to track down in order to load the core file. The tests added will test the order of precedence. It does this by creating a core file with: - NT_FILE entry with a path of "/path/nt_file_foo" - AT_EXECFN in the aux vector with a path of "/path/execfn_foo" - NT_PRPSINFO entry with a path of "prpsinfo_foo" We then test that the correct entry is found as the best path option is removed from the core file.