On Wed, Mar 31, 2021 at 08:07:18PM +0000, Sean Christopherson wrote: > On Wed, Mar 31, 2021, Kees Cook wrote: > > On Wed, Mar 24, 2021 at 10:45:36PM +0000, Sean Christopherson wrote: > > > On Tue, Mar 23, 2021, Sami Tolvanen wrote: > > > > On Tue, Mar 23, 2021 at 9:36 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > > > > > > > On Tue, Mar 23, 2021, Sami Tolvanen wrote: > > > > > > On Mon, Mar 22, 2021 at 4:44 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > Merge module sections only when using Clang LTO. With gcc-10, merging > > > > > > > sections does not appear to update the symbol tables for the module, > > > > > > > e.g. 'readelf -s' shows the value that a symbol would have had, if > > > > > > > sections were not merged. > > > > > > > > > > > > I'm fine with limiting this to LTO only, but it would be helpful to > > > > > > understand which sections are actually getting merged here. > > > > > > > > > > It doesn't appear to matter which sections get merged, the tables only show the > > > > > correct data if there is no merging whatsoever, e.g. allowing merging for any > > > > > one of the four types (.bss, .data, .rodata and .text) results in breakage. > > > > > AFAICT, merging any sections causes the layout to change and throw off the > > > > > symbol tables. > > > > > > > > Thanks for the clarification. I can reproduce this issue with gcc + > > > > bfd if any of the sections are merged, but gcc + lld produces valid > > > > symbol tables. > > > > > > FWIW, clang + bfd also produces mangled tables, so it does appear to be bfd > > > specific. > > > > Are you able to open a bug against bfd for this? > > Yes? I'll ping you when I run into trouble ;-) Hm, I can't tell if any of these are duplicates: https://sourceware.org/bugzilla/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=SUSPENDED&bug_status=WAITING&bug_status=REOPENED&component=ld&list_id=59962&product=binutils&query_format=advanced&short_desc=symbol&short_desc_type=allwordssubstr -- Kees Cook
