Re: How to enable MM debugging?

[Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>]

On 11/29/2016 05:17 PM, Andrei Borzenkov wrote:
> On Tue, Nov 29, 2016 at 4:52 PM, Stanislav Kholmanskikh
> <stanislav.kholmanskikh@oracle.com> wrote:
>> Hi!
>>
>> Does anybody use MM debugging? If so, what is the recommended/working
>> way of enabling it?
>>
>> These steps do not work:
>>
>> 1. Run ./configure with '--enable-mm-debug'. It reports:
>>
>> With memory debugging: Yes
>>
>> 2. Then build and install the binaries, and install the boot loader
>>
>> 3. Then set 'grub_mm_debug=1' in the grub's prompt.
>>
> 
> This environment variable is not used.
> 
>> grub> set grub_mm_debug=1
>> grub> insmod ofnet
>> grub>
>>
>> During initialization, ofnet calls grub_malloc(), so I expect some debug
>> messages to be printed on 'insmod ofnet'.
>>
>> Am I missing something, or is it a bug?
>>
> 
> Either patch grub to assign grub_mm_debug=1 in grub-core/kern/mm.c or
> create simple command to do it at run-time. The latter may be
> considered for inclusion, although honestly I am not sure how
> particular useful mm debugging is.

No, it doesn't help. Look:

stas@skholman-m7 grub]$ git diff grub-core/hello/hello.c
diff --git a/grub-core/hello/hello.c b/grub-core/hello/hello.c
index 456b7c3..c61bab8 100644
--- a/grub-core/hello/hello.c
+++ b/grub-core/hello/hello.c
@@ -34,6 +34,9 @@ grub_cmd_hello (grub_extcmd_context_t ctxt
__attribute__ ((unused)),
                char **args __attribute__ ((unused)))
 {
   grub_printf ("%s\n", _("Hello World"));
+
+  grub_mm_debug = 0;
+
   return 0;
 }

[stas@skholman-m7 grub]$

fails to build with:

hello/hello.c: In function ‘grub_cmd_hello’:
hello/hello.c:38: error: ‘grub_mm_debug’ undeclared (first use in this
function)
hello/hello.c:38: error: (Each undeclared identifier is reported only once
hello/hello.c:38: error: for each function it appears in.)

whereas include/grub/mm.h is included.

As for why I need this. I'm working on

http://lists.gnu.org/archive/html/grub-devel/2016-11/msg00124.html

in particular on that piece of code which is to free card memory on
module unload. And I'm considering enabling MM debugging as an
additional option to verify that I call grub_free() for all the required
buffers.




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