Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> writes:
> @@ -983,6 +983,7 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
> {
> unsigned int offset, size;
> struct xstate_header header;
> + int last_off;
> int i;
>
> /*
> @@ -1006,7 +1007,17 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
>
> __copy_xstate_to_kernel(kbuf, &header, offset, size, size_total);
>
> + last_off = 0;
> +
> for (i = 0; i < XFEATURE_MAX; i++) {
> + /*
> + * Clear uninitialized area before XSAVE header.
> + */
> + if (i == FIRST_EXTENDED_XFEATURE) {
> + memset(kbuf + last_off, 0, XSAVE_HDR_OFFSET - last_off);
> + last_off = XSAVE_HDR_OFFSET + XSAVE_HDR_SIZE;
> + }
> +
> /*
> * Copy only in-use xstates:
> */
> @@ -1020,11 +1031,16 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
> if (offset + size > size_total)
> break;
>
> + memset(kbuf + last_off, 0, offset - last_off);
> + last_off = offset + size;
> +
> __copy_xstate_to_kernel(kbuf, src, offset, size, size_total);
> }
>
> }
>
> + memset(kbuf + last_off, 0, size_total - last_off);
Why doing all this partial zeroing? There is absolutely no point.
Either the caller clears the buffer or this function clears it right at
the beginning with:
memset(kbuf, 0, min(size_total, XSAVE_MAX_SIZE));
Thanks,
tglx
