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Perform small writes before sending OK. 

To speed up downloads, OpenOCD sends gdb OK when a write is received,
even before the write has actually occurred. The failure is then
returned for the next write. That leads to the following confusing
behavior:
```
(gdb) p/x *((int*)0xdeadbeef)=8675309
$2 = 0x845fed
(gdb) p/x *((int*)0x80000000)=6874742
Cannot access memory at address 0x80000000
```
While it's actually the first write that failed.

This change hacks around this problem by not sending OK for small writes
(len<8) until the write has actually occurred. This does not impact
download speed, since during downloads (almost) all writes will have
much larger length.

Change-Id: I1f8b9bb19b0707487f840df6871e372e4ba228dd
Signed-off-by: Tim Newsome <tim@sifive.com>
Reviewed-on: http://openocd.zylin.com/3803
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
This commit is contained in:
Tim Newsome 2016-10-05 07:57:38 -07:00 committed by Andreas Fritiofson
parent 4b50872ffe
commit 19df456a79
1 changed files with 27 additions and 10 deletions
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37
src/server/gdb_server.c
View File

@ -1473,6 +1473,10 @@ static int gdb_write_memory_binary_packet(struct connection *connection,
uint32_t len = 0;
int retval = ERROR_OK;
/* Packets larger than fast_limit bytes will be acknowledged instantly on
* the assumption that we're in a download and it's important to go as fast
* as possible. */
uint32_t fast_limit = 8;
/* skip command character */
packet++;
@ -1493,19 +1497,23 @@ static int gdb_write_memory_binary_packet(struct connection *connection,
struct gdb_connection *gdb_connection = connection->priv;
if (gdb_connection->mem_write_error) {
if (gdb_connection->mem_write_error)
retval = ERROR_FAIL;
if (retval == ERROR_OK) {
if (len >= fast_limit) {
/* By replying the packet *immediately* GDB will send us a new packet
* while we write the last one to the target.
* We only do this for larger writes, so that users who do something like:
* p *((int*)0xdeadbeef)=8675309
* will get immediate feedback that that write failed.
*/
gdb_put_packet(connection, "OK", 2);
}
} else {
retval = gdb_error(connection, retval);
/* now that we have reported the memory write error, we can clear the condition */
gdb_connection->mem_write_error = false;
}
/* By replying the packet *immediately* GDB will send us a new packet
* while we write the last one to the target.
*/
if (retval == ERROR_OK)
gdb_put_packet(connection, "OK", 2);
else {
retval = gdb_error(connection, retval);
if (retval != ERROR_OK)
return retval;
}
@ -1518,6 +1526,15 @@ static int gdb_write_memory_binary_packet(struct connection *connection,
gdb_connection->mem_write_error = true;
}
if (len < fast_limit) {
if (retval != ERROR_OK) {
gdb_error(connection, retval);
gdb_connection->mem_write_error = false;
} else {
gdb_put_packet(connection, "OK", 2);
}
}
return ERROR_OK;
}