On 04/07/23 17:57, Jan Beulich wrote:
On 29.06.2023 21:20, Stefano Stabellini wrote:
On Thu, 29 Jun 2023, Luca Fancellu wrote:
On 29 Jun 2023, at 11:06, Nicola Vetrini <nicola.vetr...@bugseng.com> wrote:
--- a/xen/common/xmalloc_tlsf.c
+++ b/xen/common/xmalloc_tlsf.c
@@ -140,9 +140,7 @@ static inline void MAPPING_SEARCH(unsigned long *r, int
*fl, int *sl)
*fl = flsl(*r) - 1;
*sl = (*r >> (*fl - MAX_LOG2_SLI)) - MAX_SLI;
*fl -= FLI_OFFSET;
- /*if ((*fl -= FLI_OFFSET) < 0) // FL will be always >0!
- *fl = *sl = 0;
- */
+ ASSERT( *fl >= 0 );
I’ve checked the codebase for usage of ASSERT, but I’ve not seen use of it with
spaces
before and after the condition (like our if conditions) so I think they can be
dropped.
Yes, that's right. I am OK with this patch but I think we should wait
for Jan's ack to be sure.
An alternative that I feel more comfortable in Acking myself because it
doesn't change the semantics of this code would be to change the 3 lines
of code above with this:
/*
* ; FL will be always >0!
* if ((*fl -= FLI_OFFSET) < 0)
* fl = *sl = 0;
*/
While I'd be okay with this form, as Luca says it'll get us a different
violation, which we ought to avoid. While I was the one to suggest the
conversion to ASSERT(), having thought about it yet once more I'm now
of the opinion that _any_ transformation of this commented out piece of
code needs first understanding what was originally meant. Or
alternatively, while converting to #if form, to add a comment making
crystal clear that it's simply uncertain what was meant.
About the violation of D4.4: the Directive was never considered for
compliance because it's an advisory directive, and hence considerably
less urgent.
Having looked a bit at the surrounding code, since *fl and *sl are used
as array indices later in 'FIND_SUITABLE_BLOCK', I suggest using
something along the lines of "If *fl ever becomes < 0, reset it to a
safe value." (either using the form suggested by Stefano or an #if 0).
In any case this should become a standalone patch, right?
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)
