On Tue, 2025-08-26 at 13:17 -0700, Yonghong Song wrote: [...] > I tried with gcc14 and can reproduced the issue described in the above. > I build the kernel like below with gcc14 > make KCFLAGS='-O3' -j > and get the following build error > WARN: resolve_btfids: unresolved symbol bpf_strnchr > make[2]: *** [/home/yhs/work/bpf-next/scripts/Makefile.vmlinux:91: vmlinux] Error 255 > make[2]: *** Deleting file 'vmlinux' > Checking the symbol table: > 22276: ffffffff81b15260 249 FUNC LOCAL DEFAULT 1 bpf_strnchr.cons[...] > 235128: ffffffff81b1f540 296 FUNC GLOBAL DEFAULT 1 bpf_strnchr > and the disasm code: > bpf_strnchr: > ... > > bpf_strchr: > ... > bpf_strnchr.constprop.0 > ... > > So in symbol table, we have both bpf_strnchr.constprop.0 and bpf_strnchr. > For such case, pahole will skip func bpf_strnchr hence the above resolve_btfids > failure. > > The solution in this patch can indeed resolve this issue. It looks like instead of adding __noclone there is an option to improve pahole's filtering of ambiguous functions. Abstractly, there is nothing wrong with having a clone of a global function that has undergone additional optimizations. As long as the original symbol exists, everything should be fine. Since kfuncs are global, this should guarantee that the compiler does not change their signature, correct? Does this also hold for LTO builds? If so, when pahole sees a set of symbols like [foo, foo.1, foo.2, ...], with 'foo' being global and the rest local, then there is no real need to filter out 'foo'. Wdyt? [...]
