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. I've been following this, just didn't got to process it, will do it soon. - Arnaldo > See [0] for when this causes big problems. > > [0] https://lore.kernel.org/bpf/CAEf4BzZ0-sihSL-UAm21JcaCCY92CqfNxycHRZYXcoj8OYb=wA@xxxxxxxxxxxxxx/ > > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > --- > btf_encoder.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/btf_encoder.c b/btf_encoder.c > index c711f124b31e..672b9943a4e2 100644 > --- a/btf_encoder.c > +++ b/btf_encoder.c > @@ -538,6 +538,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > cu__for_each_variable(cu, core_id, pos) { > uint32_t size, type, linkage; > const char *name, *dwarf_name; > + const struct tag *tag; > uint64_t addr; > int id; > > @@ -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, > break; > } > > + tag = cu__type(cu, var->ip.tag.type); > + if (tag__size(tag, cu) == 0) { > + if (btf_elf__verbose) > + fprintf(stderr, "Ignoring zero-sized per-CPU variable '%s'...\n", dwarf_name ?: "<missing name>"); > + continue; > + } > + > type = var->ip.tag.type + type_id_off; > linkage = var->external ? BTF_VAR_GLOBAL_ALLOCATED : BTF_VAR_STATIC; > > -- > 2.30.2 > -- - Arnaldo
