* [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables @ 2021-05-24 23:42 Andrii Nakryiko 2021-05-25 19:58 ` Arnaldo Carvalho de Melo 2021-05-27 14:55 ` Arnaldo Carvalho de Melo 0 siblings, 2 replies; 10+ messages in thread From: Andrii Nakryiko @ 2021-05-24 23:42 UTC (permalink / raw) To: dwarves, acme, bpf, jolsa; +Cc: andrii, kernel-team 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@mail.gmail.com/ Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- 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 ^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-24 23:42 [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables Andrii Nakryiko @ 2021-05-25 19:58 ` Arnaldo Carvalho de Melo 2021-05-27 14:55 ` Arnaldo Carvalho de Melo 1 sibling, 0 replies; 10+ messages in thread From: Arnaldo Carvalho de Melo @ 2021-05-25 19:58 UTC (permalink / raw) To: Andrii Nakryiko; +Cc: dwarves, bpf, jolsa, kernel-team 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@mail.gmail.com/ > > Signed-off-by: Andrii Nakryiko <andrii@kernel.org> > --- > 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 ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-24 23:42 [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables Andrii Nakryiko 2021-05-25 19:58 ` Arnaldo Carvalho de Melo @ 2021-05-27 14:55 ` Arnaldo Carvalho de Melo 2021-05-27 14:58 ` Arnaldo Carvalho de Melo 2021-05-27 16:43 ` Andrii Nakryiko 1 sibling, 2 replies; 10+ messages in thread From: Arnaldo Carvalho de Melo @ 2021-05-27 14:55 UTC (permalink / raw) To: Andrii Nakryiko; +Cc: dwarves, bpf, jolsa, kernel-team 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@mail.gmail.com/ > +++ 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 ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-27 14:55 ` Arnaldo Carvalho de Melo @ 2021-05-27 14:58 ` Arnaldo Carvalho de Melo 2021-05-27 15:27 ` Michal Suchánek 2021-05-27 16:43 ` Andrii Nakryiko 1 sibling, 1 reply; 10+ messages in thread From: Arnaldo Carvalho de Melo @ 2021-05-27 14:58 UTC (permalink / raw) To: Michal Suchánek; +Cc: Andrii Nakryiko, dwarves, bpf, jolsa, kernel-team 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@mail.gmail.com/ I also added this: Reported-by: Michal Suchánek <msuchanek@suse.de> Michal, so you tested this patch and verified it fixed the problem? If so please let me know so that I also add: Tested-by: Michal Suchánek <msuchanek@suse.de> 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 ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-27 14:58 ` Arnaldo Carvalho de Melo @ 2021-05-27 15:27 ` Michal Suchánek 2021-05-27 15:38 ` Arnaldo Carvalho de Melo 2021-05-27 16:45 ` Andrii Nakryiko 0 siblings, 2 replies; 10+ messages in thread From: Michal Suchánek @ 2021-05-27 15:27 UTC (permalink / raw) To: Arnaldo Carvalho de Melo Cc: Andrii Nakryiko, dwarves, bpf, jolsa, kernel-team 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@mail.gmail.com/ > > I also added this: > > Reported-by: Michal Suchánek <msuchanek@suse.de> > > 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@suse.de> > > 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 ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-27 15:27 ` Michal Suchánek @ 2021-05-27 15:38 ` Arnaldo Carvalho de Melo 2021-05-27 16:47 ` Arnaldo Carvalho de Melo 2021-05-27 16:45 ` Andrii Nakryiko 1 sibling, 1 reply; 10+ messages in thread From: Arnaldo Carvalho de Melo @ 2021-05-27 15:38 UTC (permalink / raw) To: Michal Suchánek; +Cc: Andrii Nakryiko, dwarves, bpf, jolsa, kernel-team Em Thu, May 27, 2021 at 05:27:58PM +0200, Michal Suchánek escreveu: > 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@mail.gmail.com/ > > > > I also added this: > > > > Reported-by: Michal Suchánek <msuchanek@suse.de> > > > > 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. Ok, I'm test building with torvalds/master, will try with linux-next afterwards, Thanks, - Arnaldo > Thanks > > Michal > > > > > Tested-by: Michal Suchánek <msuchanek@suse.de> > > > > 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 -- - Arnaldo ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-27 15:38 ` Arnaldo Carvalho de Melo @ 2021-05-27 16:47 ` Arnaldo Carvalho de Melo 2021-05-28 6:24 ` Michal Suchánek 0 siblings, 1 reply; 10+ messages in thread From: Arnaldo Carvalho de Melo @ 2021-05-27 16:47 UTC (permalink / raw) To: Michal Suchánek; +Cc: Andrii Nakryiko, dwarves, bpf, jolsa, kernel-team Em Thu, May 27, 2021 at 12:38:38PM -0300, Arnaldo Carvalho de Melo escreveu: > Em Thu, May 27, 2021 at 05:27:58PM +0200, Michal Suchánek escreveu: > > 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@mail.gmail.com/ > > > > > > I also added this: > > > > > > Reported-by: Michal Suchánek <msuchanek@suse.de> > > > > > > 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. > > Ok, I'm test building with torvalds/master, will try with linux-next > afterwards, I build and booted torvalds/master, all seems to work, now moving to linux-next. > Thanks, > > - Arnaldo > > > Thanks > > > > Michal > > > > > > > > Tested-by: Michal Suchánek <msuchanek@suse.de> > > > > > > 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 > > -- > > - Arnaldo -- - Arnaldo ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-27 16:47 ` Arnaldo Carvalho de Melo @ 2021-05-28 6:24 ` Michal Suchánek 0 siblings, 0 replies; 10+ messages in thread From: Michal Suchánek @ 2021-05-28 6:24 UTC (permalink / raw) To: Arnaldo Carvalho de Melo Cc: Andrii Nakryiko, dwarves, bpf, jolsa, kernel-team On Thu, May 27, 2021 at 01:47:41PM -0300, Arnaldo Carvalho de Melo wrote: > Em Thu, May 27, 2021 at 12:38:38PM -0300, Arnaldo Carvalho de Melo escreveu: > > Em Thu, May 27, 2021 at 05:27:58PM +0200, Michal Suchánek escreveu: > > > 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@mail.gmail.com/ > > > > > > > > I also added this: > > > > > > > > Reported-by: Michal Suchánek <msuchanek@suse.de> > > > > > > > > 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. > > > > Ok, I'm test building with torvalds/master, will try with linux-next > > afterwards, > > I build and booted torvalds/master, all seems to work, now moving to > linux-next. [ 9s] /usr/bin/qemu-kvm -nodefaults -no-reboot -nographic -vga none -cpu host -object rng-random,filename=/dev/random,id=rng0 -device virtio-rng-pci,rng=rng0 -runas qemu -net none -kernel /var/cache/obs/worker/root_2/.mount/boot/kernel -initrd /var/cache/obs/worker/root_2/.mount/boot/initrd -append root=/dev/disk/by-id/virtio-0 rootfstype=ext4 rootflags=noatime ext4.allow_unsupported=1 mitigations=off panic=1 quiet no-kvmclock elevator=noop nmi_watchdog=0 rw rd.driver.pre=binfmt_misc console=ttyS0 init=/.build/build -m 8192 -drive file=/var/cache/obs/worker/root_2/root,format=raw,if=none,id=disk,cache=unsafe -device virtio-blk-pci,drive=disk,serial=0 -drive file=/var/cache/obs/worker/root_2/swap,format=raw,if=none,id=swap,cache=unsafe -device virtio-blk-pci,drive=swap,serial=1 -serial stdio -chardev socket,id=monitor,server,nowait,path=/var/cache/obs/worker/root_2/root.qemu/monitor -mon chardev=monitor,mode=readline -smp 8 [ 9s] c[?7l[2J[0mSeaBIOS (version rel-1.14.0-0-g155821a-rebuilt.opensuse.org) [ 15s] Booting from ROM..c[?7l[2J### VM INTERACTION END ### [ 15s] 2nd stage started in virtual machine [ 15s] machine type: x86_64 [ 15s] Linux version: 5.13.0-rc3-next-2[ 5.210478] sysrq: Changing Loglevel [ 15s] 0210526-2.g3bd43[ 5.211566] sysrq: Loglevel set to 4 [ 15s] 9f-vanilla #1 SMP Thu May 27 18:27:17 UTC 2021 (3bd439f) [ 15s] Increasing log level from now on... [ 15s] Enable sysrq operations [ 15s] Setting up swapspace version 1, size = 2 GiB (2097147904 bytes) [ 15s] no label, UUID=6e22796c-6df5-4859-a291-24acde2e92e5 [ 15s] swapon: /dev/vdb: found signature [pagesize=4096, signature=swap] [ 15s] swapon: /dev/vdb: pagesize=4096, swapsize=2097152000, devsize=2097152000 [ 15s] swapon /dev/vdb [ 15s] WARNING: udev not running, creating extra device nodes [ 15s] logging output to //.build.log... next-20210527 does not build becuase of missing symbol but next-20210526 built with the patched pahole boots. Tested-by: Michal Suchánek <msuchanek@suse.de> Thanks Michal > > > Thanks, > > > > - Arnaldo > > > > > Thanks > > > > > > Michal > > > > > > > > > > > Tested-by: Michal Suchánek <msuchanek@suse.de> > > > > > > > > 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 > > > > -- > > > > - Arnaldo > > -- > > - Arnaldo ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-27 15:27 ` Michal Suchánek 2021-05-27 15:38 ` Arnaldo Carvalho de Melo @ 2021-05-27 16:45 ` Andrii Nakryiko 1 sibling, 0 replies; 10+ messages in thread From: Andrii Nakryiko @ 2021-05-27 16:45 UTC (permalink / raw) To: Michal Suchánek Cc: Arnaldo Carvalho de Melo, Andrii Nakryiko, dwarves, bpf, Jiri Olsa, Kernel Team On Thu, May 27, 2021 at 8:37 AM Michal Suchánek <msuchanek@suse.de> wrote: > > 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@mail.gmail.com/ > > > > I also added this: > > > > Reported-by: Michal Suchánek <msuchanek@suse.de> > > > > 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. > I've posted a link to it in your thread [0]. [0] https://lore.kernel.org/bpf/CAEf4BzZ9=aLVD7ytgCcSxcbOLqFNK-p1mj14Rv_TGnOyL3aO_g@mail.gmail.com/ > Given that linux-next does not build for me at the moment > I don't think I will test it soon. This patch applied to pahole master will fix linux-next build. > > Thanks > > Michal > > > > > Tested-by: Michal Suchánek <msuchanek@suse.de> > > > > 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 ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables 2021-05-27 14:55 ` Arnaldo Carvalho de Melo 2021-05-27 14:58 ` Arnaldo Carvalho de Melo @ 2021-05-27 16:43 ` Andrii Nakryiko 1 sibling, 0 replies; 10+ messages in thread From: Andrii Nakryiko @ 2021-05-27 16:43 UTC (permalink / raw) To: Arnaldo Carvalho de Melo Cc: Andrii Nakryiko, dwarves, bpf, Jiri Olsa, Kernel Team On Thu, May 27, 2021 at 7:55 AM Arnaldo Carvalho de Melo <acme@kernel.org> wrote: > > 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@mail.gmail.com/ > > > +++ 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? yeah, no problem > > Thanks, applied! Thanks! > > - Arnaldo ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2021-05-28 6:24 UTC | newest] Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-05-24 23:42 [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables Andrii Nakryiko 2021-05-25 19:58 ` Arnaldo Carvalho de Melo 2021-05-27 14:55 ` Arnaldo Carvalho de Melo 2021-05-27 14:58 ` Arnaldo Carvalho de Melo 2021-05-27 15:27 ` Michal Suchánek 2021-05-27 15:38 ` Arnaldo Carvalho de Melo 2021-05-27 16:47 ` Arnaldo Carvalho de Melo 2021-05-28 6:24 ` Michal Suchánek 2021-05-27 16:45 ` Andrii Nakryiko 2021-05-27 16:43 ` Andrii Nakryiko
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