Thanks for the patch! + Marcus Marcus can you please test the below patch and provide your tested-by and reported-by tags? On Fri, Sep 8, 2023 at 4:47 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > > On Thu, Sep 07, 2023 at 10:33:00PM +0200, Jiri Olsa wrote: > > On Thu, Sep 07, 2023 at 12:01:18PM -0700, Nick Desaulniers wrote: > > > So we've got a curious report recently: > > > https://github.com/ClangBuiltLinux/linux/issues/1913 > > > > > > ld.lld: error: ld-temp.o <inline asm>:14577:1: symbol > > > '__BTF_ID__struct__cgroup__624' is already defined > > > __BTF_ID__struct__cgroup__624: > > > ^ > > > > > > It's been hard to pin down a SHA and .config to reproduce this, but > > > looking at the definition of BTF_ID's usage of __ID's usage of > > > __COUNTER__, and the two statements: > > > > > > kernel/bpf/helpers.c:2460:BTF_ID(struct, cgroup) > > > kernel/bpf/verifier.c:5075:BTF_ID(struct, cgroup) > > > > > > Is it possible that __COUNTER__ could evaluate to the same value > > > across 2 different translation units, leading to a name collision like > > > the above? > > > > hum, that probably the case, I see same counter values at different > > __BTF_ID_ symbols: > > > > ffffffff833fe540 r __BTF_ID__struct__bpf_bloom_filter__380 > > ffffffff833fe548 r __BTF_ID__struct__bpf_queue_stack__380 > > ffffffff833fe578 r __BTF_ID__struct__cgroup__380 > > > > perhaps we were just lucky not to hit that :-\ > > > > > > > > looking at another usage of BTF_ID other than struct > > > cgroup;kernel/bpf/helpers.c:2461:BTF_ID(func, bpf_cgroup_release) > > > is only defined in one translation unit > > > > > > Should one of those two `BTF_ID(struct, cgroup)` be removed? Is there > > > some other way we can avoid these collisions in the future? > > > > need to find some way to make the symbol unique, will check > > the change below uses object's path as the __BTF_ID_.. symbol suffix to make > it unique > > I'm still looking, but can't think of a better way so far, perhaps somebody > will have better idea Another good approach; I had simply added __LINE__ into the paste. https://github.com/ClangBuiltLinux/linux/issues/1913#issuecomment-1710794319 Which just makes the probability of this occurring again smaller, but still non-zero. + Masahiro for thoughts on the invocation of echo and base32. Looks like base32 is part of coreutils. Kind of strange that coreutils isn't listed in Documentation/process/changes.rst. Would adding the usage of base32 add a new dependency on coreutils? > > jirka > > > --- > diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h > index a3462a9b8e18..564953f9cbc7 100644 > --- a/include/linux/btf_ids.h > +++ b/include/linux/btf_ids.h > @@ -49,7 +49,7 @@ word \ > ____BTF_ID(symbol, word) > > #define __ID(prefix) \ > - __PASTE(prefix, __COUNTER__) > + __PASTE(__PASTE(prefix, __COUNTER__), BTF_ID_BASE) Do we still need __COUNTER__ if we're now using BTF_ID_BASE? > > /* > * The BTF_ID defines unique symbol for each ID pointing > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index 68d0134bdbf9..2ef8b2798be0 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -200,6 +200,10 @@ _c_flags += $(if $(patsubst n%,, \ > -D__KCSAN_INSTRUMENT_BARRIERS__) > endif > > +ifeq ($(CONFIG_DEBUG_INFO_BTF),y) > +_c_flags += -DBTF_ID_BASE=$(subst =,,$(shell echo -n $(modfile) | base32 -w0)) `man 1 base32` shows it can just read a file. Could the above be: _c_flags += -DBTF_ID_BASE=$(subst =,,$(shell base32 -w0 $(modfile))) ? (untested) Also, the output of $ base32 -w0 Documentation/process/changes.rst is 24456 characters. This is going to blow up symbol tables. I suppose ELF probably has some length limit on symbol names, too. I was nervous about my approaching appending __LINE__. Perhaps pipe the output to `head -c <n bytes>`? > +endif > + > # $(srctree)/$(src) for including checkin headers from generated source files > # $(objtree)/$(obj) for including generated headers from checkin source files > ifeq ($(KBUILD_EXTMOD),) -- Thanks, ~Nick Desaulniers
