Em Mon, May 24, 2021 at 04:42:22PM -0700, Andrii Nakryiko escreveu: > btf_encoder is ignoring zero-sized per-CPU ELF symbols, but the same has to be > done for DWARF variables when matching them with ELF symbols. This is due to > zero-sized DWARF variables matching unrelated (non-zero-sized) variable that > happens to be allocated at the exact same address, leading to a lot of > confusion in BTF. > See [0] for when this causes big problems. > [0] https://lore.kernel.org/bpf/CAEf4BzZ0-sihSL-UAm21JcaCCY92CqfNxycHRZYXcoj8OYb=wA@xxxxxxxxxxxxxx/ > +++ b/btf_encoder.c > @@ -550,6 +551,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > /* addr has to be recorded before we follow spec */ > addr = var->ip.addr; > + dwarf_name = variable__name(var, cu); > > /* DWARF takes into account .data..percpu section offset > * within its segment, which for vmlinux is 0, but for kernel > @@ -582,11 +584,9 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > * modules per-CPU data section has non-zero offset so all > * per-CPU symbols have non-zero values. > */ > - if (var->ip.addr == 0) { > - dwarf_name = variable__name(var, cu); > + if (var->ip.addr == 0) > if (!dwarf_name || strcmp(dwarf_name, name)) > continue; > - } > > if (var->spec) > var = var->spec; > @@ -600,6 +600,13 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, I just changed the above hunk to be: @@ -583,7 +585,6 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, * per-CPU symbols have non-zero values. */ if (var->ip.addr == 0) { - dwarf_name = variable__name(var, cu); if (!dwarf_name || strcmp(dwarf_name, name)) continue; } Which is shorter and keeps the {} around a multi line if block, ok? Thanks, applied! - Arnaldo
