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Date:      Sun, 24 May 2020 11:24:40 +0200 (CEST)
From:      Paul FLOYD <pjfloyd@wanadoo.fr>
To:        FreeBSD Hackers <freebsd-hackers@freebsd.org>
Subject:   Re: SIGBUS si_code 12
Message-ID:  <816299859.1977.1590312280071.JavaMail.www@wwinf1c21>
In-Reply-To: <20200522201251.GM64045@kib.kiev.ua>
References:  <2102917207.11671.1589487524169.JavaMail.www@wwinf1n11> <490544208.11847.1589489181927.JavaMail.www@wwinf1n11> <20200514224347.GB46537@kib.kiev.ua> <9840EA0E-CF11-4332-A5A0-A3CDBA0F0464@wanadoo.fr> <20200521154621.GB85681@raichu> <068F2B99-24C2-4F38-ACC1-02273C198434@wanadoo.fr> <679A6BE4-E344-49D0-B76D-DB65A41E26FA@wanadoo.fr> <20200522192804.GL64045@kib.kiev.ua> <D22F2087-4FB3-4EB5-841E-61C809DF94F0@wanadoo.fr> <20200522201251.GM64045@kib.kiev.ua>

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=C2=A0
=C2=A0
=C2=A0
> > And which files/functions do that?
> ELF image activator.

> Look in kern/imgact_elf.c. It is basically in check_note, used from
> get_brandinfo. The real function names are mangled for co-existence
> of 32 and 64 bit elf activators.

That's quite interesting. If I run procstat -b on a running Valgrind instan=
ce I see

=C2=A0
aulf> procstat -b 2072
PID COMM OSREL PATH
2072 memcheck-amd64-free 0 /usr/home/paulf/scratch/valgrind/memcheck/memche=
ck-amd64-freebsd

A quick recap of Valgrind execution

'valgrind' itself is just a small stub executable that looks at the guest e=
xecutable to determine if it is amd64 or x86. It will then do an execve of =
the required tool e.g., memcheck-amd64-freebsd.=20
The tools themselves are entirely standalone and do not link with any libra=
ries, not even libc.

Is there a way to get the linker to add a .note section with osrel?

If not, is there a way to set osrel after a process has started?

A+
Paul






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