Userspace guest address offsetting

Re-implement GUEST_BASE support.
Offset guest ddress space by default if the guest binary contains
regions below the host mmap_min_addr.
Implement support for i386, x86-64 and arm hosts.

Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
Signed-off-by: Paul Brook <paul@codesourcery.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index d31cca7..d4c9274 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1545,6 +1545,29 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs,
     info->mmap = 0;
     elf_entry = (abi_ulong) elf_ex.e_entry;
 
+#if defined(CONFIG_USE_GUEST_BASE)
+    /*
+     * In case where user has not explicitly set the guest_base, we
+     * probe here that should we set it automatically.
+     */
+    if (!have_guest_base) {
+        /*
+         * Go through ELF program header table and find out whether
+	 * any of the segments drop below our current mmap_min_addr and
+         * in that case set guest_base to corresponding address.
+         */
+        for (i = 0, elf_ppnt = elf_phdata; i < elf_ex.e_phnum;
+            i++, elf_ppnt++) {
+            if (elf_ppnt->p_type != PT_LOAD)
+                continue;
+            if (HOST_PAGE_ALIGN(elf_ppnt->p_vaddr) < mmap_min_addr) {
+                guest_base = HOST_PAGE_ALIGN(mmap_min_addr);
+                break;
+            }
+        }
+    }
+#endif /* CONFIG_USE_GUEST_BASE */
+
     /* Do this so that we can load the interpreter, if need be.  We will
        change some of these later */
     info->rss = 0;