On Wed, Apr 22, 2026 at 9:04 PM Josh Poimboeuf <[email protected]> wrote: > > Rewrite the symbol correlation code, using a tiered list of > deterministic strategies in a loop. For duplicately named symbols, each > tier applies a filter with the goal of finding a 1:1 deterministic > correlation between the original and patched version of the symbol. > > Overall this works much better than the existing algorithm, particularly > with LTO kernels.
I found it is hard to follow all the matching algorithms here. Could you please add some examples for each case: different levels in find_twin(), match in find_twin_suffixed(), and match in find_twin_positional()? Also a few nitpicks below. > Signed-off-by: Josh Poimboeuf <[email protected]> > --- [...] > +static struct symbol *find_twin(struct elfs *e, struct symbol *sym1) > +{ > + struct symbol *name_last = NULL, *scope_last = NULL, > + *file_last = NULL, *csum_last = NULL; > + unsigned int name_orig = 0, name_patched = 0; > + unsigned int scope_orig = 0, scope_patched = 0; > + unsigned int file_orig = 0, file_patched = 0; > + unsigned int csum_orig = 0, csum_patched = 0; > + struct symbol *sym2, *match = NULL; > + > + /* Count orig candidates */ > + for_each_sym_by_demangled_name(e->orig, sym1->demangled_name, sym2) { > + if (sym2->twin || sym1->type != sym2->type || > dont_correlate(sym2) || > + (!maybe_same_file(sym1, sym2))) > continue; > > - count++; > - result = sym2; > + /* Level 1: name match (widest filter) */ > + name_orig++; > + > + /* Level 2: scope (scope changes allowed) */ > + if (is_tu_local_sym(sym1) != is_tu_local_sym(sym2)) is_tu_local_sym(sym1) is called many times, shall we add a variable for it? > + continue; > + scope_orig++; > + > + /* Level 3: file (scope changes disallowed) */ > + if (!same_file(sym1, sym2)) > + continue; > + file_orig++; > + > + /* Level 4: checksum (unchanged symbols) */ > + if (sym1->len != sym2->len || !sym1->csum.checksum || > + sym1->csum.checksum != sym2->csum.checksum) > + continue; > + csum_orig++; > } > > - if (count > 1) { > - ERROR("Multiple (%d) correlation candidates for %s", count, > sym->name); > - return -1; > + /* Count patched candidates */ > + for_each_sym_by_demangled_name(e->patched, sym1->demangled_name, > sym2) { > + if (sym2->twin || sym1->type != sym2->type || > dont_correlate(sym2)) > + continue; > + > + /* Level 1 */ > + if (!maybe_same_file(sym1, sym2)) > + continue; This for_each_sym_by_demangled_name() has two "if () continue" while the first one has one. Maybe keep them the same (just for symmetry)? Thanks, Song > + name_patched++; > + name_last = sym2; > + [...]
