loader: add rom transaction API

Image file loaders may add a series of roms.  If an error occurs partway
through loading there is no easy way to drop previously added roms.

This patch adds a transaction mechanism that works like this:

  rom_transaction_begin();
  ...call rom_add_*()...
  rom_transaction_end(ok);

If ok is false then roms added in this transaction are dropped.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20180814162739.11814-5-stefanha@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/hw/loader.h b/include/hw/loader.h
index e98b84b8f9..5235f119a3 100644
--- a/include/hw/loader.h
+++ b/include/hw/loader.h
@@ -225,6 +225,25 @@ int rom_check_and_register_reset(void);
 void rom_set_fw(FWCfgState *f);
 void rom_set_order_override(int order);
 void rom_reset_order_override(void);
+
+/**
+ * rom_transaction_begin:
+ *
+ * Call this before of a series of rom_add_*() calls.  Call
+ * rom_transaction_end() afterwards to commit or abort.  These functions are
+ * useful for undoing a series of rom_add_*() calls if image file loading fails
+ * partway through.
+ */
+void rom_transaction_begin(void);
+
+/**
+ * rom_transaction_end:
+ * @commit: true to commit added roms, false to drop added roms
+ *
+ * Call this after a series of rom_add_*() calls.  See rom_transaction_begin().
+ */
+void rom_transaction_end(bool commit);
+
 int rom_copy(uint8_t *dest, hwaddr addr, size_t size);
 void *rom_ptr(hwaddr addr, size_t size);
 void hmp_info_roms(Monitor *mon, const QDict *qdict);