Re: [PATCH v4] livepatch: introduce shadow variable API

[Joe Lawrence]

On 08/17/2017 10:05 AM, Petr Mladek wrote:
> On Mon 2017-08-14 16:02:43, Joe Lawrence wrote:
>> [ ... snip ... ]
>> +	/* Allocate a new shadow variable for use inside the lock below */
>> +	new_shadow = kzalloc(size + sizeof(*new_shadow), gfp_flags);
> 
> We should print an error message when the memory cannot be allocated.
> Otherwise we will return NULL without explanation. It will be
> especially helpful when a caller forgets to check for NULL.

Interesting, I hadn't seen this checkpatch complaint before:

WARNING: Possible unnecessary 'out of memory' message
#416: FILE: kernel/livepatch/shadow.c:143:
+       if (!new_shadow) {
+               pr_err("failed to allocate shadow variable <0x%p, %lu>\n",

Discussion thread:
https://lkml.org/lkml/2014/6/10/382

Think the stack trace that the memory subsystem would emit is good
enough, or would you like to see <obj, id> for debugging purposes?

-- Joe