> > + KMSAN_WARN_ON(!src_slots || !dst_slots);
> > + KMSAN_WARN_ON((src_slots < 1) || (dst_slots < 1));
>
> The above 2 checks look equivalent.
Right, I'll drop the first one.
> > + KMSAN_WARN_ON((src_slots - dst_slots > 1) ||
> > + (dst_slots - src_slots < -1));
> > + backwards = dst > src;
> > + i = backwards ? min(src_slots, dst_slots) - 1 : 0;
> > + iter = backwards ? -1 : 1;
> > +
> > + align_shadow_src =
> > + (u32 *)ALIGN_DOWN((u64)shadow_src, KMSAN_ORIGIN_SIZE);
> > + for (step = 0; step < min(src_slots, dst_slots); step++, i += iter) {
> > + KMSAN_WARN_ON(i < 0);
> > + shadow = align_shadow_src[i];
> > + if (i == 0) {
> > + /*
> > + * If |src| isn't aligned on KMSAN_ORIGIN_SIZE, don't
> > + * look at the first |src % KMSAN_ORIGIN_SIZE| bytes
> > + * of the first shadow slot.
> > + */
> > + skip_bits = ((u64)src % KMSAN_ORIGIN_SIZE) * 8;
> > + shadow = (shadow << skip_bits) >> skip_bits;
>
> Is this correct?...
> For the first slot we want to ignore some of the first (low) bits. To
> ignore low bits we need to shift right and then left, no?
Yes, you are right, I forgot about the endianness. Will try to add
some tests for this case.
> > + }
> > + if (i == src_slots - 1) {
> > + /*
> > + * If |src + n| isn't aligned on
> > + * KMSAN_ORIGIN_SIZE, don't look at the last
> > + * |(src + n) % KMSAN_ORIGIN_SIZE| bytes of the
> > + * last shadow slot.
> > + */
> > + skip_bits = (((u64)src + n) % KMSAN_ORIGIN_SIZE) * 8;
> > + shadow = (shadow >> skip_bits) << skip_bits;
>
> Same here.
Done
>
> This can be a bit shorted and w/o the temp var as:
>
> new_origin = kmsan_internal_chain_origin(old_origin);
> /*
> * kmsan_internal_chain_origin() may return
> * NULL, but we don't want to lose the previous
> * origin value.
> */
> if (!new_origin)
> new_origin = old_origin;
Done.
>
>
> > + }
> > + if (shadow)
> > + origin_dst[i] = new_origin;
>
> Are we sure that origin_dst is aligned here?
Yes, kmsan_get_metadata(..., KMSAN_META_ORIGIN) always returns aligned pointers.
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
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