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CVS commit: src/tests/lib/libc/gen

Module Name:    src
Committed By:   jym
Date:           Fri Apr 20 00:40:32 UTC 2012

Modified Files:
        src/tests/lib/libc/gen: t_siginfo.c

Log Message:
ATF test for SIGBUS => BUS_ADRALN (invalid address alignment).

That one is tedious to test under x86: alignment exceptions are
not reported by this architecture unless you ask for them explicitely (by
setting the PSL_AC bit). The brokenness does not end there: %cr2 should
contain the address where the unaligned access occured, alas, it does not.

I am not aware of other architectures where this could happen. Still, my
knowledge is limited; if there is one, feel free to send me a mail and I
will update the test accordingly.

Adding insult to injury, this test can fail in various funny ways with VMs:
- under x86 QEMU, no trap() happens. As ring 3 code stays almost untouched by
QEMU VMM, I suppose the exception can only be triggered when the host
itself is capable of catching unaligned accesses.
- under Virtual Box with HVM support, i386 works fine, but amd64 fails with a
SIGILL (Illegal instruction) that happens right before entering the
signal handler. No idea why, and trying to debug it with gdb freezes the VM
(including ddb breaks).

Anyway, tested with:
- i386: P4 host, anita, Virtual Box HVM (Mac OS X)
- amd64: anita, Virtual Box HVM (Mac OS X)

XXX I would appreciate if someone could test it under a real amd64 host with
an up-to-date kernel, so I can reasonably assume that the culprit is
Virtual Box and not our amd64 port (my test machine being off line
I cannot do it myself). Results from other arches would be a plus too.

Initial issue reported by Nicolas Joly on port-amd64. Thanks!

To generate a diff of this commit:
cvs rdiff -u -r1.14 -r1.15 src/tests/lib/libc/gen/t_siginfo.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

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