arm7_9: Avoid infinite loops in bulk write dispatching

Add a mandatory field in struct arm7_9_common for regular, non-optimized
memory writes. Together with the existing bulk_memory_write field, this
allows variants to select any combination of implementations for regular
and bulk writes, without risking infinite loops from accidentally using
bulk writes for implementing bulk writes.

ARM 7/9 targets may now select arm7_9_memory_write_opt as their
target.write_memory implementation, which will dispatch to
arm7_9_common.bulk_write_memory if possible, or fallback to
arm7_9_common.write_memory otherwise.

To avoid loops, bulk write implementations mustn't call any other
functions than arm7_9_write_memory_no_opt() to write memory; it will
unconditionally call arm7_9_common.write_memory. If they fail, they should
simply return error to allow the caller to fallback to regular writes.

Tested on a regular ARM7TDMI only.

Change-Id: Iae42a6e093e2df68c4823c927d757ae8f42ef388
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/1685
Tested-by: jenkins
Reviewed-by: Sergey A. Borshch <sb-sf@users.sourceforge.net>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/target/arm7_9_common.h b/src/target/arm7_9_common.h
index 85e5ac0..5821e13 100644
--- a/src/target/arm7_9_common.h
+++ b/src/target/arm7_9_common.h
@@ -120,6 +120,13 @@ struct arm7_9_common {
 	/**< Callback function called before restoring the processor context */
 
 	/**
+	 * Variant specific memory write function that does not dispatch to bulk_write_memory.
+	 * Used as a fallback when bulk writes are unavailable, or for writing data needed to
+	 * do the bulk writes.
+	 */
+	int (*write_memory)(struct target *target, uint32_t address,
+			uint32_t size, uint32_t count, const uint8_t *buffer);
+	/**
 	 * Write target memory in multiples of 4 bytes, optimized for
 	 * writing large quantities of data.
 	 */
@@ -160,6 +167,8 @@ int arm7_9_write_memory(struct target *target, uint32_t address,
 		uint32_t size, uint32_t count, const uint8_t *buffer);
 int arm7_9_write_memory_opt(struct target *target, uint32_t address,
 		uint32_t size, uint32_t count, const uint8_t *buffer);
+int arm7_9_write_memory_no_opt(struct target *target, uint32_t address,
+		uint32_t size, uint32_t count, const uint8_t *buffer);
 int arm7_9_bulk_write_memory(struct target *target, uint32_t address,
 		uint32_t count, const uint8_t *buffer);