Introduce guest mem offset, static link example launcher
In order to avoid problematic special linking of the Launcher, we give
the Host an offset: this means we can use any memory region in the
Launcher as Guest memory rather than insisting on mmap() at 0.
The result is quite pleasing: a number of casts are replaced with
simple additions.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index a0788c1..eb95860 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -325,8 +325,8 @@
* Dealing With Guest Memory.
*
* When the Guest gives us (what it thinks is) a physical address, we can use
- * the normal copy_from_user() & copy_to_user() on that address: remember,
- * Guest physical == Launcher virtual.
+ * the normal copy_from_user() & copy_to_user() on the corresponding place in
+ * the memory region allocated by the Launcher.
*
* But we can't trust the Guest: it might be trying to access the Launcher
* code. We have to check that the range is below the pfn_limit the Launcher
@@ -348,8 +348,8 @@
/* Don't let them access lguest binary. */
if (!lguest_address_ok(lg, addr, sizeof(val))
- || get_user(val, (u32 __user *)addr) != 0)
- kill_guest(lg, "bad read address %#lx", addr);
+ || get_user(val, (u32 *)(lg->mem_base + addr)) != 0)
+ kill_guest(lg, "bad read address %#lx: pfn_limit=%u membase=%p", addr, lg->pfn_limit, lg->mem_base);
return val;
}
@@ -357,7 +357,7 @@
void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val)
{
if (!lguest_address_ok(lg, addr, sizeof(val))
- || put_user(val, (u32 __user *)addr) != 0)
+ || put_user(val, (u32 *)(lg->mem_base + addr)) != 0)
kill_guest(lg, "bad write address %#lx", addr);
}
@@ -367,7 +367,7 @@
void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
{
if (!lguest_address_ok(lg, addr, bytes)
- || copy_from_user(b, (void __user *)addr, bytes) != 0) {
+ || copy_from_user(b, lg->mem_base + addr, bytes) != 0) {
/* copy_from_user should do this, but as we rely on it... */
memset(b, 0, bytes);
kill_guest(lg, "bad read address %#lx len %u", addr, bytes);
@@ -379,7 +379,7 @@
unsigned bytes)
{
if (!lguest_address_ok(lg, addr, bytes)
- || copy_to_user((void __user *)addr, b, bytes) != 0)
+ || copy_to_user(lg->mem_base + addr, b, bytes) != 0)
kill_guest(lg, "bad write address %#lx len %u", addr, bytes);
}
/* (end of memory access helper routines) :*/
@@ -616,11 +616,9 @@
*
* Note that if the Guest were really messed up, this
* could happen before it's done the INITIALIZE
- * hypercall, so lg->lguest_data will be NULL, so
- * &lg->lguest_data->cr2 will be address 8. Writing
- * into that address won't hurt the Host at all,
- * though. */
- if (put_user(cr2, &lg->lguest_data->cr2))
+ * hypercall, so lg->lguest_data will be NULL */
+ if (lg->lguest_data
+ && put_user(cr2, &lg->lguest_data->cr2))
kill_guest(lg, "Writing cr2");
break;
case 7: /* We've intercepted a Device Not Available fault. */