Re: [parisc-linux] Latest 2.6.13-rc6-pa2 test pr :_(

[Randolph Chung <randolph@tausq.org>]

> Still don't know.  I have been working on the java testsuite which
> appears to cause most of the kernel bugs.  I fixed a bug last weekend
> where the signal handler caused a SIGSEGV.  An incorrect count was
> used to copy a mmapped block.  We still have a problem with PR218.exe.
> The DWARF unwind fails to stop and allocates a huge amount of memory.
> PR218 is a simple test to test whether the runtime can catch a null
> pointer exception from a leaf routine.  I think there is a bug in
> MD_FALLBACK_FRAME_STATE_FOR.  It replaces the %r2 value with the
> iaoq[0] value and I think this fails when we need to unwind through
> a leaf function which doesn't save %r2.

Can you explain more where this is broken?

I'm assuming you are talking about this bit of code:

     134   fs->regs.reg[2].how = REG_SAVED_OFFSET;
     135   fs->regs.reg[2].loc.offset = (long) &sc->sc_iaoq[0] - new_cfa;
     136   fs->retaddr_column = 2;

sc_iaoq[0] should be the pc when the signal handler was triggered, so it 
shouldn't matter if it's a leaf func or not. We are simply telling the 
unwinder that reg[2] has the return address of the current (signal 
handler) function, and the value of reg[2] can be computed with a stack 
offset. When is this wrong?

randolph
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