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>

1 files changed, 10 insertions, 8 deletions

diff --git a/drivers/lguest/io.c b/drivers/lguest/io.c
index ea68613b43f6..3a845335fee8 100644
--- a/drivers/lguest/io.c
+++ b/drivers/lguest/io.c
@@ -186,7 +186,7 @@ int bind_dma(struct lguest *lg,
          * we're doing this. */
         mutex_lock(&lguest_lock);
         down_read(fshared);
-        if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
+        if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
                 kill_guest(lg, "bad dma key %#lx", ukey);
                 goto unlock;
         }
@@ -247,7 +247,8 @@ static int lgread_other(struct lguest *lg,
                         void *buf, u32 addr, unsigned bytes)
 {
         if (!lguest_address_ok(lg, addr, bytes)
-            || access_process_vm(lg->tsk, addr, buf, bytes, 0) != bytes) {
+            || access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr,
+                                 buf, bytes, 0) != bytes) {
                 memset(buf, 0, bytes);
                 kill_guest(lg, "bad address in registered DMA struct");
                 return 0;
@@ -261,8 +262,8 @@ static int lgwrite_other(struct lguest *lg, u32 addr,
                          const void *buf, unsigned bytes)
 {
         if (!lguest_address_ok(lg, addr, bytes)
-            || (access_process_vm(lg->tsk, addr, (void *)buf, bytes, 1)
-                != bytes)) {
+            || access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr,
+                                 (void *)buf, bytes, 1) != bytes) {
                 kill_guest(lg, "bad address writing to registered DMA");
                 return 0;
         }
@@ -318,7 +319,7 @@ static u32 copy_data(struct lguest *srclg,
                  * copy_to_user_page(), and some arch's seem to need special
                  * flushes.  x86 is fine. */
                 if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE,
-                                   (void __user *)src->addr[si], len) != 0) {
+                                   srclg->mem_base+src->addr[si], len) != 0) {
                         /* If a copy failed, it's the source's fault. */
                         kill_guest(srclg, "bad address in sending DMA");
                         totlen = 0;
@@ -377,7 +378,8 @@ static u32 do_dma(struct lguest *srclg, const struct lguest_dma *src,
                  * number of pages.  Note that we're holding the destination's
                  * mmap_sem, as get_user_pages() requires. */
                 if (get_user_pages(dstlg->tsk, dstlg->mm,
-                                   dst->addr[i], 1, 1, 1, pages+i, NULL)
+                                   (unsigned long)dstlg->mem_base+dst->addr[i],
+                                   1, 1, 1, pages+i, NULL)
                     != 1) {
                         /* This means the destination gave us a bogus buffer */
                         kill_guest(dstlg, "Error mapping DMA pages");
@@ -493,7 +495,7 @@ again:
         mutex_lock(&lguest_lock);
         down_read(fshared);
         /* Get the futex key for the key the Guest gave us */
-        if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
+        if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
                 kill_guest(lg, "bad sending DMA key");
                 goto unlock;
         }
@@ -584,7 +586,7 @@ unsigned long get_dma_buffer(struct lguest *lg,
 
         /* This can fail if it's not a valid address, or if the address is not
          * divisible by 4 (the futex code needs that, we don't really). */
-        if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) {
+        if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
                 kill_guest(lg, "bad registered DMA buffer");
                 goto unlock;
         }