From: Christian Deacon <gamemann@gflclan.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: xdp-newbies@vger.kernel.org
Subject: Re: XDP BPF Stack Limit Issues
Date: Thu, 17 Dec 2020 20:42:15 -0600 [thread overview]
Message-ID: <992798d6-2f41-afbe-608c-3987dd90593b@gflclan.com> (raw)
In-Reply-To: <20201217095016.1f38e06c@carbon>
Thank you for pointing this out Jesper! I'm honestly surprised I didn't
realize this before.
I've made this change and I'm able to compile the XDP/BPF program
without any issues now.
Thank you again!
On 12/17/2020 2:50 AM, Jesper Dangaard Brouer wrote:
> I have to look elsewhere[2] to see that:
> #define MAX_FILTERS 55
>
> Your problem is that you create an array with 55 pointers each 8 bytes
> equal 440 bytes on the stack (max stack is 512). Why do you need to
> lookup all 55 map elements in a loop before using them?
>
> https://gist.github.com/gamemann/663674924e16286b02a835637912c2a5#file-xdp_fw_ipv6_maps-c-L267
>
> struct filter *filter[MAX_FILTERS];
> for (uint8_t i = 0; i < MAX_FILTERS; i++)
> {
> key = i;
>
> filter[i] = bpf_map_lookup_elem(&filters_map, &key);
> }
> [...]
> for (uint8_t i = 0; i < MAX_FILTERS; i++)
> {
> // Check if ID is above 0 (if 0, it's an invalid rule).
> if (!filter[i] || filter[i]->id < 1)
> [...]
prev parent reply other threads:[~2020-12-18 2:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-16 15:29 XDP BPF Stack Limit Issues Christian Deacon
2020-12-17 8:50 ` Jesper Dangaard Brouer
2020-12-18 2:42 ` Christian Deacon [this message]
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