chain.c: do a proper copy operation for the cmldr signature

Instead of writing into memory that we might not own, create a proper
copy operation using syslinux_add_movelist().

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/com32/modules/chain.c b/com32/modules/chain.c
index 1ae20d4..c515488 100644 (file)
--- a/com32/modules/chain.c
+++ b/com32/modules/chain.c
@@ -455,6 +455,7 @@ static void do_boot(void *boot_sector, size_t boot_size,
     uint8_t swapdrive = driveno & 0x80;
     int i;
     addr_t loadbase = opt.seg ? (opt.seg << 4) : 0x7c00;
+    static const char cmldr_signature[8] = "cmdcons";
 
     mmap = syslinux_memory_map();
 
@@ -470,10 +471,21 @@ static void do_boot(void *boot_sector, size_t boot_size,
 
     endimage = loadbase + boot_size;
 
-    if (syslinux_add_movelist
-       (&mlist, loadbase, (addr_t) boot_sector, boot_size))
+    if (syslinux_add_movelist(&mlist, loadbase,
+                             (addr_t) boot_sector, boot_size))
        goto enomem;
 
+    /*
+     * To boot the Recovery Console of Windows NT/2K/XP we need to write
+     * the string "cmdcons\0" to memory location 0000:7C03.
+     * Memory location 0000:7C00 contains the bootsector of the partition.
+     */
+    if (opt.cmldr) {
+       if (syslinux_add_movelist(&mlist, 0x7c03, (addr_t)cmldr_signature,
+                                 sizeof cmldr_signature))
+           goto enomem;
+    }
+
     if (opt.swap && driveno != swapdrive) {
        static const uint8_t swapstub_master[] = {
            /* The actual swap code */
@@ -886,13 +898,6 @@ int main(int argc, char *argv[])
            }
        }
 
-    /* To boot the Recovery Console of Windows NT/2K/XP we need to write
-       the string "cmdcons\0" to memory location 0000:7C03.
-       Memory location 0000:7C00 contains the bootsector of the partition.
-     */
-    if (opt.cmldr)
-        strcpy((char *) 0x7c03, "cmdcons");
-
     } else if (partinfo) {
        /* Actually read the boot sector */
        /* Pick the first buffer that isn't already in use */