block: Check for read/write requests over 64K

The standard BIOS disk read/write request interface should never get a
request for more than 64K of data.  Explicitly check for overly large
requests and reject them.  This way, the low-level drivers do not need
to check for or attempt to handle very large requests.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/disk.c b/src/disk.c
index fe2e2c31..0e0af24b 100644
--- a/src/disk.c
+++ b/src/disk.c
@@ -173,6 +173,7 @@ disk_1300(struct bregs *regs, struct drive_s *drive_gf)
     struct disk_op_s dop;
     dop.drive_gf = drive_gf;
     dop.command = CMD_RESET;
+    dop.count = 0;
     int status = send_disk_op(&dop);
     disk_ret(regs, status);
 }
@@ -322,6 +323,7 @@ disk_1310(struct bregs *regs, struct drive_s *drive_gf)
     struct disk_op_s dop;
     dop.drive_gf = drive_gf;
     dop.command = CMD_ISREADY;
+    dop.count = 0;
     int status = send_disk_op(&dop);
     disk_ret(regs, status);
 }