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SubjectRe: Linux 4.3 kallsyms_lookup_name not returning per_cpu symbol values
From
Take that back, I just reproduced it again.  Seems to affect random
symbols not just per cpu. I'll research some more.



On 11/18/15, Jeffrey Merkey <jeffmerkey@gmail.com> wrote:
> I tracked this down and it turns out to be a page mapping problem with
> one of the sound drivers on the system trashing memory. It's a bug,
> but a bug in a vendor supplied driver.
>
> Jeff
>
> On 11/18/15, Jeffrey Merkey <jeffmerkey@gmail.com> wrote:
>> kallsyms_lookup_name is not returning per_cpu symbols when called.
>> The symbols show up when you run something with the kallsyms_iter
>> struct but not through the regular interface. I have looked through
>> the code and I am not able to determine with certainty if its designed
>> this way or just busted. Any help with this would be appreciated.
>>
>> The following code does display the per_cpu symbols, they just don't
>> seem to show up when called from kallsyms_lookup_name.
>>
>>
>> struct kallsym_iter mdb_iter;
>> int mdb_kallsyms(char *str, int (*print)(char *s, ...))
>> {
>> register loff_t pos = 0;
>> register struct kallsym_iter *iter = &mdb_iter;
>>
>> if (!print)
>> return 0;
>>
>> // set to beginning of the kallsyms list
>> reset_iter(iter, 0);
>> while (1)
>> {
>> // search the kallsyms list
>> if (!update_iter(iter, pos++))
>> break;
>>
>> if (!iter->name[0])
>> continue;
>>
>> // if an exclusion search was specified, skip non-matching entries
>> if (str && *str && !strstr(iter->name, str))
>> continue;
>>
>> if (iter->module_name[0])
>> {
>> if (print("%0*lx %c %s [%s]\n", (int)(2*sizeof(void*)),
>> iter->value, iter->type, iter->name,
>> iter->module_name))
>> return 1;
>> }
>> else
>> {
>> if (print("%0*lx %c %s\n", (int)(2*sizeof(void*)),
>> iter->value, iter->type, iter->name))
>> return 1;
>> }
>> }
>> return 0;
>> }
>> EXPORT_SYMBOL_GPL(mdb_kallsyms);
>>
>


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