On Tue, Jun 11, 2024 at 09:56:51AM +0800, Zheng Yejian wrote: > On 2024/6/7 23:02, Peter Zijlstra wrote: > > Oh gawd, sodding weak functions again. > > > > I would suggest changing scipts/kallsyms.c to emit readily identifiable > > symbol names for all the weak junk, eg: > > > > __weak_junk_NNNNN > > > > Sorry for the late reply, I just had a long noon holiday :> > > scripts/kallsyms.c is compiled and used to handle symbols in vmlinux.o > or vmlinux.a, see kallsyms_step() in scripts/link-vmlinux.sh, those > overridden weak symbols has been removed from symbol table of vmlinux.o > or vmlinux.a. But we can found those symbols from original xx/xx.o file, > for example, the weak free_initmem() in in init/main.c is overridden, > its symbol is not in vmlinx but is still in init/main.o . > > How about traversing all origin xx/xx.o and finding all weak junk symbols ? You don't need to. ELF symbl tables have an entry size for FUNC type objects, this means that you can readily find holes in the text and fill them with a symbol. Specifically, you can check the mcount locations against the symbol table and for every one that falls in a hole, generate a new junk symbol. Also see 4adb23686795 where objtool adds these holes to the ignore/unreachable code check. The lack of size for kallsyms is in a large part what is causing the problems.
