memory alignment problems with -current on amd64? [Found Cause]

[Mark Atkinson]

Alan Cox wrote:
> On Tue, Feb 10, 2009 at 2:20 PM, Mark Atkinson <atkin901 at yahoo.com> wrote:
> [snip]
>>
>>
>>
>> Well, taking the information I knew -- OCT 15th == good, Mid DEC == BAD,
>> I trolled every commit logged between.   Eventually I found this one:
>>
>> http://svn.freebsd.org/viewvc/base?view=revision&revision=185715
>>
>> http://docs.freebsd.org/cgi/mid.cgi?200812061937.mB6JbqAI003273
>>
>> I set vm.pmap.pg_ps_enabled="0" in /boot/loader.conf, and
>> was able to complete buildworld and -j16 buildworld and -j8 buildkernel
>> no problem.
>>
>> It appears superpage mapping causes alignment problems on this box.
> 
> 
> Can you please provide more detailed information about this machine, in
> particular, the processor including the revision?  It would also be
> helpful to see what gdb says about a couple of these crashes,
> specifically, the machine registers at the time of the exception.

Looking at the core a little further, you probably want the registers at the 
frame before the signal handler is called.

[...]
#61 0x178d2d478b6062af in ?? ()
#62 0x000000000000000a in ?? ()
#63 0x0000000000504620 in ?? ()
#64 0x0000000000000001 in ?? ()
#65 <signal handler called>
#66 0x0000000000444d68 in ?? ()
#67 0x0000000000000000 in ?? ()
#68 0x0000000000000001 in ?? ()
#69 0x0000000800ce0f30 in ?? ()
[...]

(gdb) frame 66
#66 0x0000000000444d68 in ?? ()
(gdb) info registers
rax            0x0      0
rbx            0x1      1
rcx            0x8019ff030      34386997296
rdx            0x1      1
rsi            0x8019ff060      34386997344
rdi            0x8019fe0a0      34386993312
rbp            0x801a00000      0x801a00000
rsp            0x7fffffffe180   0x7fffffffe180
r8             0x2      2
r9             0x0      0
r10            0x1      1
r11            0x801a00000      34387001344
r12            0x801a00000      34387001344
r13            0x800ce0f30      34373242672
r14            0x8019fe060      34386993248
r15            0x0      0
rip            0x444d68 0x444d68
eflags         0x297    663
cs             0x2b     43
ss             0x23     35
ds             0x0      0
es             0x0      0
fs             0x0      0
gs             0x0      0

-- 
Mark Atkinson
atkin901 at yahoo.com
(!wired)?(coffee++):(wired);