Hello, On Thu, May 27, 2021 at 11:58:24AM -0300, Arnaldo Carvalho de Melo wrote: > Em Thu, May 27, 2021 at 11:55:10AM -0300, Arnaldo Carvalho de Melo escreveu: > > 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/ > > I also added this: > > Reported-by: Michal Suchánek <msuchanek@xxxxxxx> > > Michal, so you tested this patch and verified it fixed the problem? If > so please let me know so that I also add: This is the first time I see this patch. Given that linux-next does not build for me at the moment I don't think I will test it soon. Thanks Michal > > Tested-by: Michal Suchánek <msuchanek@xxxxxxx> > > Thanks, > > - Arnaldo > > > > +++ 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 > > -- > > - Arnaldo
