xscale: check that wp length does not exceed address
authorMike Dunn <mikedunn@newsguy.com>
Sun, 19 Sep 2010 21:48:51 +0000 (14:48 -0700)
committerØyvind Harboe <oyvind.harboe@zylin.com>
Mon, 20 Sep 2010 07:21:12 +0000 (09:21 +0200)
Hi everyone,

A while back I sent in a patch that adds support for watchpoint lengths greater
than four on xscale.  It's been working well, until the other day, when it
caused an unexpected debug exception.  Looking into this I realized there is a
case where it breaks: when the length arg is greater than the base address.
This is a consequence of the way the hardware works.  Don't see a work-around,
so I added code to xscale_add_watchpoint() to check for and disallow this

Some more detail... xscale watchpoint hardware does not support a length
directly.  Instead, a mask value can be specified (not to be confused with the
optional mask arg to the wp command, which xscale does not support).  Any bits
set in the mask are ignored when the watchpoint hardware compares the access
address to the watchpoint address.  So as long as the length is a power of two,
setting the mask to length-1 effectively specifies the length.  Or so I thought,
until I realized that if the length exceeds the base address, *all* bits of the
base address are ignored by the comaparator, and the watchpoint range
effectively becomes 0 .. length.

Questions, comments, criticisms gratefully received.


Signed-off-by: Mike Dunn <mikedunn@newsguy.com>

index 77f0f1b8927756906e446f1ad47fb5ff57105ada..37a243857c7f3baa6d1078b64101435a86778070 100644 (file)
@@ -2401,6 +2401,13 @@ static int xscale_add_watchpoint(struct target *target,
+       if (watchpoint->length > watchpoint->address)
+       {
+          LOG_ERROR("xscale does not support watchpoints with length "
+                                "greater than address");
+       }
        xscale->dbr_available = 0;
        return ERROR_OK;

Linking to existing account procedure

If you already have an account and want to add another login method you MUST first sign in with your existing account and then change URL to read https://review.openocd.org/login/?link to get to this page again but this time it'll work for linking. Thank you.

SSH host keys fingerprints

1024 SHA256:YKx8b7u5ZWdcbp7/4AeXNaqElP49m6QrwfXaqQGJAOk gerrit-code-review@openocd.zylin.com (DSA)
384 SHA256:jHIbSQa4REvwCFG4cq5LBlBLxmxSqelQPem/EXIrxjk gerrit-code-review@openocd.org (ECDSA)
521 SHA256:UAOPYkU9Fjtcao0Ul/Rrlnj/OsQvt+pgdYSZ4jOYdgs gerrit-code-review@openocd.org (ECDSA)
256 SHA256:A13M5QlnozFOvTllybRZH6vm7iSt0XLxbA48yfc2yfY gerrit-code-review@openocd.org (ECDSA)
256 SHA256:spYMBqEYoAOtK7yZBrcwE8ZpYt6b68Cfh9yEVetvbXg gerrit-code-review@openocd.org (ED25519)
+--[ED25519 256]--+
|=..              |
|+o..   .         |
|*.o   . .        |
|+B . . .         |
|Bo. = o S        |
|Oo.+ + =         |
|oB=.* = . o      |
| =+=.+   + E     |
|. .=o   . o      |
2048 SHA256:0Onrb7/PHjpo6iVZ7xQX2riKN83FJ3KGU0TvI0TaFG4 gerrit-code-review@openocd.zylin.com (RSA)