[CRIU] [PATCH 4/4] arch: x86 -- Add proxification of vDSO calls

[Cyrill Gorcunov]

On Wed, Apr 17, 2013 at 05:06:13PM +0400, Pavel Emelyanov wrote:
> > +	/*
> > +	 * Proxify vdso content.
> > +	 */
> > +	if (vdso_proxy->proxify) {
> > +		void *base_to, *base_from;
> > +
> > +		base_to = decode_pointer(vma_premmaped_start(&vdso_proxy->vma_to->vma));
> > +		base_from = decode_pointer(vma_premmaped_start(&vdso_proxy->sym_from->vma));
> > +
> > +		/*
> > +		 * Fill new vDSO with content of run-time vDSO
> > +		 */
> > +		pr_debug("vdso: Copy run-time contents %p -> %p\n",
> > +			 (void *)vdso_proxy->sym_rt.vma_start, base_to);
> > +
> > +		memcpy(base_to, (void *)vdso_proxy->sym_rt.vma_start,
> > +		       symtable_vma_size(&vdso_proxy->sym_rt));
> > +
> > +		if (arch_proxify_vdso(base_to, base_from,
> > +				      &vdso_proxy->sym_rt,
> > +				      &vdso_proxy->sym_dumpee))
> > +			return -1;
> 
> I don't get this. You put into task's VDSO address a VDSO-proxy with the memcpy above
> and tune jump offsets with arch_proxify_vdso. Where is the new VDSO itself?

read_vmas
	...
+		if (vma_entry_is(&vma->vma, VMA_AREA_VDSO)) {
+			pr_debug("vdso: Got dumpee area %lx-%lx\n",
+				 (long)vma->vma.start, (long)vma->vma.end);
+
+			vdso_proxy.sym_from = vma;
+		}
+

then

+	if (vdso_proxy.proxify) {
+		if (vdso_proxy.sym_from) {
+			struct vma_area *last;
+			struct vma_area *vma;
+
+			ret = -1;
+			vma = alloc_vma_area();
+			if (!vma)
+				goto out;
+
+			last = list_entry(rst_vmas.h.prev, struct vma_area, list);
+			rst_vmas.nr++;
+			list_add_tail(&vma->list, &rst_vmas.h);
	Cyrill