Date: Fri, 22 May 2020 09:27:25 +0200 From: Paul Floyd <pjfloyd@wanadoo.fr> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: SIGBUS si_code 12 Message-ID: <068F2B99-24C2-4F38-ACC1-02273C198434@wanadoo.fr> In-Reply-To: <20200521154621.GB85681@raichu> 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>
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> On 21 May 2020, at 17:46, Mark Johnston <markj@freebsd.org> wrote: >> > > Assuming that the context is valgrind, the issue is probably that the > client program is being run with without a NT_FREEBSD_ABI_TAG note, so > the kernel does not have p_osrel defined for the client process and thus > reverts to the legacy behaviour of delivering SIGBUS with UCODE_PAGEFLT. > This behaviour is not documented since it is only present for > compatibility with old binaries. > > valgrind should probably embed the NT_FREEBSD_ABI_TAG note from the > target executable into the client process somehow. Hi Mark You assume correctly, this is in the context of running under Valgrind. It’s one of the regression test suite applications, memcheck/tests/addressable I hadn’t noticed that the executable was generating SIGSEGV when running standalone. The test runs a loop 5 fimes, each time round the loop it forks and the child calls a function that will generate one kind of SIGBUS or SIGSEGV. The parent just checks that the child died with one of these signals. I just ran the executable under gdb and I do see that the error that was posing a problem does generate a SIGSEGV with si_cde 2. Back in Valgrind, nothing is currently being done with NT_FREEBSD_ABI_TAG, The only thing that I can see that is of this nature is the read elf code that is looking for the buildid. I’ll have a go at seeing if I can read the value of NT_FREEBSD_ABI_TAG, but I’m not sure what to do with it at the moment. A+ Paul
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