Re: [PATCH] softmmu/memory: use memcpy for multi-byte accesses

[Peter Maydell <peter.maydell@linaro.org>]

On Tue, 14 Nov 2023 at 21:18, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 11/14/23 12:55, Patrick Venture wrote:
> > Avoids unaligned pointer issues.
> >
> > Reviewed-by: Chris Rauer <crauer@google.com>
> > Reviewed-by: Peter Foley <pefoley@google.com>
> > Signed-off-by: Patrick Venture <venture@google.com>
> > ---
> >   system/memory.c | 16 ++++++++--------
> >   1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/system/memory.c b/system/memory.c
> > index 304fa843ea..02c97d5187 100644
> > --- a/system/memory.c
> > +++ b/system/memory.c
> > @@ -1343,16 +1343,16 @@ static uint64_t memory_region_ram_device_read(void *opaque,
> >
> >       switch (size) {
> >       case 1:
> > -        data = *(uint8_t *)(mr->ram_block->host + addr);
> > +        memcpy(&data, mr->ram_block->host + addr, sizeof(uint8_t));
>
>
> This is incorrect, especially for big-endian hosts.
>
> You want to use "qemu/bswap.h", ld*_he_p(), st*_he_p().

More specifically, we have a ldn_he_p() and stn_he_p() that
take the size in bytes of the data to read, so we should be
able to replace the switch-on-size in these functions with
a single call to the appropriate one of those.

thanks
-- PMM