Re: Bad unwinder data for __kernel_sigtramp_rt64 in PPC 64 vDSO corrupts Condition Register

[Andrew Haley]

Jakub Jelinek writes:
 > On Tue, Oct 16, 2007 at 07:22:31PM +0100, Andrew Haley wrote:
 > >  > and similarly linux-unwind.h should do:
 > >  > 
 > >  >     fs->regs.reg[R_CR2].loc.offset = (long) &regs->ccr - new_cfa;
 > >  >     /* CR? regs are just 32-bit and PPC is big-endian.  */
 > >  >     fs->regs.reg[R_CR2].loc.offset += sizeof (long) - 4;
 > > 
 > > Won't this generate an alignment fault?
 > 
 > Why?  The reg size is 32-bit, so it only should be read/written
 > as 32-bit value.
 > E.g. a brief look at _Unwind_RaiseException shows:
 >      lwz 12,5656(1)
 > ...
 >         mtcrf 32,12      #,
 >         ld 15,5368(1)    #,
 >         ld 16,5376(1)    #,
 >         mtcrf 16,12      #,
 >         ld 17,5384(1)    #,
 >         ld 18,5392(1)    #,
 >         mtcrf 8,12       #,
 > so it shouldn't have any problems with 4 byte alignment (rather than 8 byte
 > alignment).

Yes, I think it's OK.

I was thinking about uw_install_context_1, but that should be fine, as
it uses memcpy.

Andrew.