Re: [PATCH v2 05/74] semihosting: Add target_strlen for softmmu-uaccess.h

[Richard Henderson]

On 5/16/22 08:11, Peter Maydell wrote:
> > +        chunk = -(addr | TARGET_PAGE_MASK);
>
> 'chunk' is unsigned but we're assigning it a negative number here...
> I assume this is doing some clever bit-twiddling trick but it isn't
> very obvious.

Number of bytes left in page -- I'll rename the variable.

> In any case, rounding to a page boundary isn't sufficient to
> avoid problems, because we don't mandate that RAM-to-device
> MemoryRegion boundaries happen on page boundaries. I think you
> either need to do this at a low enough level that you can
> look at what MemoryRegion types you're reading from, or you need
> to do it byte at a time.

Easy enough to use probe_access_flags.


r~