linux-kernel - RE: [PATCH] arm64: allow post-init vmalloc PXNTable

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Date: Tue, 13 Feb 2024 19:35:27 +0000
From: Maxwell Bland <mbland@...orola.com>
To: Mark Rutland <mark.rutland@....com>
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Subject: RE: [PATCH] arm64: allow post-init vmalloc PXNTable

> -----Original Message-----
> From: Maxwell Bland On Tuesday, February 13, 2024 1:15 PM
> > From: Mark Rutland <mark.rutland@....com>
> > How does this work with other allocations of executable memory? e.g.  modules,
> > BPF?
> 
> It should work.
> - kernel/bpf/core.c uses bpf_jit_alloc_exec to create executable code regions,
>   which is a wrapper for module_alloc. In the interpreted BPF case, we do not
>   need to worry since the pages storing interpreted code are NX and can be
>   marked PXNTable regardless.

Correction: I was wrong here. The _weak reference to bpf_jit_alloc_exec is overwritten in
arch/arm64/net/bpf_jit_comp.c  to use a vmalloc call. This would need to be set back to
the generic BPF's use of "module_alloc". I will look into and correct this.