Date: Fri, 22 May 2020 22:28:04 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Paul Floyd <pjfloyd@wanadoo.fr> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: SIGBUS si_code 12 Message-ID: <20200522192804.GL64045@kib.kiev.ua> In-Reply-To: <679A6BE4-E344-49D0-B76D-DB65A41E26FA@wanadoo.fr> 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>
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On Fri, May 22, 2020 at 05:32:37PM +0200, Paul Floyd wrote:
> A bit more on this.
>
> The code in question is in trap.c:
>
> if (signo == SIGSEGV) {
> ucode = SEGV_MAPERR;
> } else if (prot_fault_translation == 0) {
> /*
> * Autodetect. This check also covers
> * the images without the ABI-tag ELF
> * note.
> */
> if (SV_CURPROC_ABI() == SV_ABI_FREEBSD &&
> p->p_osrel >= P_OSREL_SIGSEGV) {
> signo = SIGSEGV;
> ucode = SEGV_ACCERR;
> } else {
> signo = SIGBUS;
> ucode = T_PAGEFLT;
> }
> } else if (prot_fault_translation == 1) {
> /*
> * Always compat mode.
> */
> signo = SIGBUS;
> ucode = T_PAGEFLT;
> } else {
> /*
> * Always SIGSEGV mode.
> */
> signo = SIGSEGV;
> ucode = SEGV_ACCERR;
> }
>
>
> I have machte.prot_fault_translation set to 0 (the default I believe) so this enters the first ‘else if’ branch.
>
> The value of p_osrel looks like it comes from retold.c. I see two mechanisms - passed via auxv AT_OSRELDATE (with a backup of using a sysctl) and reading the NT_FREEBSD_ABI_TAG note - I’m not sure which is used in this case.
I do not know what retold.c is.
>
> The auxv value seems to be sent and I can’t see why either should be failing.
auxv has nothing to do with p_osrel as seen by kernel. In-kernel
ELF image activator parses notes and reads osrel if available.
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