linux-kernel - Re: [PATCH bpf-next v3 0/3] Support kCFI + BPF on arm64

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Date: Wed, 08 May 2024 10:05:30 +0000
From: Puranjay Mohan <puranjay12@...il.com>
To: Maxwell Bland <mbland@...orola.com>, "open list:BPF [GENERAL] (Safe
 Dynamic Programs and Tools)" <bpf@...r.kernel.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon
 <will@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
 <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai
 Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu
 <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, John Fastabend
 <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Stanislav
 Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
 <jolsa@...nel.org>, Zi Shen Lim <zlim.lnx@...il.com>, Mark Rutland
 <mark.rutland@....com>, Suzuki K Poulose <suzuki.poulose@....com>, Mark
 Brown <broonie@...nel.org>, linux-arm-kernel@...ts.infradead.org, open
 list <linux-kernel@...r.kernel.org>, Josh Poimboeuf <jpoimboe@...nel.org>
Subject: Re: [PATCH bpf-next v3 0/3]  Support kCFI + BPF on arm64

Maxwell Bland <mbland@...orola.com> writes:

Hi Maxwell,

> In preparation for the BPF summit, I took a look back on BPF-CFI patches
> to check the status and found that there had been no updates for around
> a month, so I went ahead and made the fixes suggested in v2.
>
> This patchset handles emitting proper CFI hashes during JIT, which
> can cause some of the selftests to fail, and handles removing the
> __nocfi tag from bpf_dispatch_*_func on ARM, meaning Clang CFI 
> checks will be generated:
>
> 0000000000fea1e8 <bpf_dispatcher_xdp_func>:
> paciasp
> stp     x29, x30, [sp, #-0x10]!
> mov     x29, sp
> + ldur    w16, [x2, #-0x4]                           
> + movk    w17, #0x1881                               
> + movk    w17, #0xd942, lsl #16                      
> + cmp     w16, w17                                
> + b.eq    0xffff8000810016a0 <bpf_dispatcher_xdp_func+0x24>
> + brk     #0x8222   
> blr     x2
> ldp     x29, x30, [sp], #0x10
> autiasp
> ret
>
> Where ^+ indicates the additional assembly.
>
> Credit goes to Puranjay Mohan entirely for this, I just did some fixes,
> hopefully that is OK.

Thanks for taking this effort forward.

checkpatch.pl complains about the patches like the following:

ERROR: Missing Signed-off-by: line by nominal patch author 'Maxwell Bland <mbland@...orola.com>'

So, you can change the authorship of the patch like:

git commit --amend --author "Puranjay Mohan <puranjay12@...il.com>"

similar for the patch by Mark:

git commit --amend --author "Mark Rutland <mark.rutland@....com>"

Thanks,
Puranjay