Re: [Qemu-devel] [PATCH 4/5] ARM BE32 watchpoint fix.

[Julian Brown <julian@codesourcery.com>]

On Thu, 3 Nov 2016 23:14:05 +0000
Peter Maydell <peter.maydell@linaro.org> wrote:

> On 3 November 2016 at 17:30, Julian Brown <julian@codesourcery.com>
> wrote:
> > In BE32 mode, sub-word size watchpoints can fail to trigger because
> > the address of the access is adjusted in the opcode helpers before
> > being compared with the watchpoint registers.  This patch reversed
> > the address adjustment before performing the comparison.
> >
> > Signed-off-by: Julian Brown <julian@codesourcery.com>
> > ---
> >  exec.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/exec.c b/exec.c
> > index 4c84389..eadab54 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -2047,6 +2047,19 @@ static void check_watchpoint(int offset, int
> > len, MemTxAttrs attrs, int flags) return;
> >      }
> >      vaddr = (cpu->mem_io_vaddr & TARGET_PAGE_MASK) + offset;
> > +#if defined(TARGET_ARM) && !defined(CONFIG_USER_ONLY)
> > +    /* In BE32 system mode, target memory is stored byteswapped
> > (FIXME:
> > +       relative to a little-endian host system), and by the time
> > we reach here
> > +       (via an opcode helper) the addresses of subword accesses
> > have been
> > +       adjusted to account for that, which means that watchpoints
> > will not
> > +       match.  Undo the adjustment here.  */
> > +    if (arm_sctlr_b(env)) {
> > +        if (len == 1)
> > +            vaddr ^= 3;
> > +        else if (len == 2)
> > +            vaddr ^= 2;
> > +    }
> > +#endif  
> 
> No target-CPU specific code in exec.c, please...

Yeah, I'd imagine not. I struggled with this one. Any suggestions for a
better way to do this?

Thanks,

Julian