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Re: [PATCH-for-5.2 v2] trace: use STAP_SDT_V2 to work around symbol visi
From: |
Frank Ch. Eigler |
Subject: |
Re: [PATCH-for-5.2 v2] trace: use STAP_SDT_V2 to work around symbol visibility |
Date: |
Thu, 19 Nov 2020 09:38:22 -0500 |
User-agent: |
Mutt/1.12.0 (2019-05-25) |
Hi -
> > Maybe add a comment? (no need to repost if you agree):
> >
> > # Workaround to avoid dtrace(1) produces file with 'hidden'
> > # symbol visibility, define STAP_SDT_V2 to produce 'default'
> > # symbol visibility instead.
> >
> > > + QEMU_CFLAGS="$QEMU_CFLAGS -DSTAP_SDT_V2"
Please note that we don't know how long this behavior will persist.
You are relying on an accident. :-)
Much of the systemtap code doesn't support real STAP_SDT_V2 format,
and /usr/include/sys/sdt.h cannot generate it at all. That macro
tricks only the dtrace-header-generator to suppress the "hidden"
visibility attribute, but doesn't change probe metadata format to the
old V2 (in .probes sections rather than .note.* ELF notes).
We'll try not to break it, but please move toward the more proper
per-solib or per-executable hidden copies of the semaphore objects.
- FChE