Signal trampoline frame changed location on FreeBSD 9 AMD64?
John Marino
freebsdml at marino.st
Wed Jul 25 18:04:58 UTC 2012
Hi guys,
I know this isn't a thread issue, but I'm hoping one of you either knows
the answer or can point me to someone that does.
After I patched lib/libthr/thread/thr_setschedparam.c, all the threading
issues with the GNAT testsuite running on FreeBSD 9.0 disappeared. On
i386-FreeBSD, GNAT passes all tests perfectly.
This is not the case for x86_64-FreeBSD. GNAT fails all the stack-check
/ dereference tests. It can no longer detect when it's at the end of
the stack during the unwind process, because it can't find the signal
trampoline.
For FreeBSD, it was easy. Use the kern.ps_strings sysctl and subtract X
from it's address (where X is 128 on i386 and 32 on AMD64). If the
stack pointer is between the addr kern.ps_strings and addr
kern.ps_strings - X then it's at the end of the stack.
For AMD64, according to GDB, it seems the signal trampoline frame is now
ahead of the ps_strings address rather than behind it.
Who can confirm this or conversely tell me how wrong I am?
By the way, if I'm right, it also breaks the base system's GDB
end-of-stack detection as well. It uses the same algorithm.
I haven't tested this on FreeBSD 9.1 beta - just 9.0 release.
Regards,
John
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