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Re: [Xen-devel] [PATCH] xen/console: Fix build when CONFIG_DEBUG_TRACE=y


On 20/08/2019 14:12, Andrew Cooper wrote:
On 19/08/2019 19:37, Julien Grall wrote:
Hi Andrew,

On 8/19/19 7:04 PM, Andrew Cooper wrote:
On 19/08/2019 19:01, Julien Grall wrote:
Commit b5e6e1ee8da "xen/console: Don't treat NUL character as the end
of the buffer" extended sercon_puts to take the number of character
to print in argument.

Sadly, a couple of couple of the callers in debugtrace_dump_worker()
were not converted. This result to a build failure when enabling

Spotted by Travis using randconfig
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
   xen/drivers/char/console.c | 5 +++--
   1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 2c14c2ca73..924d4971ca 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -1185,11 +1185,12 @@ static void debugtrace_dump_worker(void)
         /* Print oldest portion of the ring. */
       ASSERT(debugtrace_buf[debugtrace_bytes - 1] == 0);
-    sercon_puts(&debugtrace_buf[debugtrace_prd]);
+    sercon_puts(&debugtrace_buf[debugtrace_prd],
+                strlen(&debugtrace_buf[debugtrace_prd]));

Isn't this just debugtrace_bytes - debugtrace_prd - 1 ?

I tried and it resulted to print a lot of @^ on the console. This is
because the ring may not be full.

So the portion between debugtrace_prd and debugtrace_bytes will be
full of zero.

Looking at the code again, I think this portion and either be full of
zero character or full of non-zero character. In other word, a mix
would not be possible. So how about:

if ( debugtrace_buf[debugtrace_prd] != '\0' )
               debugtrace_bytes - debugtrace_prd - 1);

LGTM.  Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Thank you! I will update the patch and commit it.


Julien Grall

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