The Debian bugzilla has a long thread about kernel crashes when
compiling ruby1.9 on hppa. This kernel bug led even to discussions if
hppa should be dropped for lenny.
See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=478717 for details.

It's really easy to reproduce the bug, and it generates this backtrace
(interestingly two backtraces):

     < Your System ate a SPARC! Gah! >
      -------------------------------
             \   ^__^
              \  (xx)\_______
                 (__)\       )\/\
                  U  ||----w |
                     ||     ||
miniruby (pid 15221): Protection id trap (code 27)

     YZrvWESTHLNXBCVMcbcbcbcbOGFRQPDI
PSW: 00000000000001000000000000001111 Not tainted
r00-03  0004000f 102a9800 101a141c 8210c388
r04-07  00000000 0020fd08 0020fd10 00000001
r08-11  00000000 8210c388 fffffff2 8210c0c8
r12-15  fb0d04c8 402cc3d8 00001000 40007000
r16-19  002120a0 00000010 0020fd90 00000001
r20-23  8210c000 00000000 0020fd0e 8210c39e
r24-27  00000000 00000001 8e7c5660 105e7a90
r28-31  0000000f 00190834 8210c500 101a12b8
sr00-03  00000000 00000000 00000000 00000847
sr04-07  00000000 00000000 00000000 00000000

IASQ: 00000000 00000000 IAOQ: 101a147c 101a1480
 IIR: 0ed5d240    ISR: 00000847  IOR: 0020fd0e
 CPU:        0   CR30: 8210c000 CR31: d22344f0
 ORIG_R28: 00001000
 IAOQ[0]: do_sys_poll+0x1ac/0x1b8
 IAOQ[1]: do_sys_poll+0x1b0/0x1b8
 RP(r2): do_sys_poll+0x14c/0x1b8
Backtrace:
 [<101a1574>] sys_poll+0x84/0xec
 [<10114078>] syscall_exit+0x0/0x28

Backtrace:
 [<1010fdb8>] die_if_kernel+0xe8/0x1ac
 [<10110584>] handle_interruption+0x2fc/0x598
 [<10113078>] intr_check_sig+0x0/0x34


The bug (sometimes but not always!) happens in fs/select.c:do_sys_poll()
when calling __put_user() and writing back fds[0].revents to userspace.
What I quite don't understand yet is, why does copy_from_user() [called
a few lines above the __put_user()] succeeds, and __put_user() sometimes
suddenly fails with a protection id fault.

The attached patch simply adds the lookup for a fixup handler when trap
#27 (protection id trap) happens in kernel space. This was missing in
the code path for trap #27 which is why the kernel then called
die_if_kernel() and crashed.

Even with this patch ruby1.9 may fail to compile, but at least the
kernel crashes are gone.

Any feedback welcome.

Helge

Signed-off-by: Helge Deller <deller@gmx.de>