Messages in this thread | | | From | Florian Weimer <> | Subject | Re: [PATCH net-next v4] net: skb: prevent the split of kfree_skb_reason() by gcc | Date | Wed, 07 Sep 2022 20:59:26 +0200 |
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* Segher Boessenkool:
> On Tue, Sep 06, 2022 at 02:37:47PM +0200, Florian Weimer wrote: >> > On Mon, Aug 22, 2022 at 4:01 PM Florian Weimer <fweimer@redhat.com> wrote: >> > I did some research on the 'sibcalls' you mentioned above. Feel like >> > It's a little similar to 'inline', and makes the callee use the same stack >> > frame with the caller, which obviously will influence the result of >> > '__builtin_return_address'. > > Sibling calls are essentially calls that can be replaced by jumps (aka > "tail call"), without needing a separate entry point to the callee. > > Different targets can have a slightly different implementation and > definition of what exactly is a sibling call, but that's the gist. > >> > Hmm......but I'm not able to find any attribute to disable this optimization. >> > Do you have any ideas? >> >> Unless something changed quite recently, GCC does not allow disabling >> the optimization with a simple attribute (which would have to apply to >> function pointers as well, not functions). > > It isn't specified what a sibling call exactly *is*, certainly not on C > level (only in the generated machine code), and the details differs per > target.
Sure, but GCC already disables this optimization in a generic fashion for noreturn calls. It should be possible to do the same based another function attribute.
Thanks, Florian
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