On Thu, Jul 17, 2025 at 6:18 AM Lorenz Bauer [off-list ref] wrote:

Hi Breno,

Thanks for reaching out.

On Thu, Jul 17, 2025 at 1:39 PM Breno Leitao [off-list ref] wrote:

quoted

Should __pa_symbol() be used instead of virt_to_phys()?

I'm not really well versed with mm in general. Looking around a bit I
found some explanation in [1]. Your suggested fix does make sense to
me based on that.

Let me run the patch against bpf-ci and see what happens.

1: https://lore.kernel.org/all/90667b2b7f773308318261f96ebefd1a67133c4c.1732464395.git.lukas@wunner.de/ (local)

Thanks for the link.
Key quote: "arm64 maps the kernel in the vmalloc space."
I think the map shouldn't be destroying linearity of kernel rodata.
__pa_symbol() should work for start_BTF, but would be good
to double check with Ard that the rest stays linear.