linux-kernel - Re: [PATCH 2/2] x86/bpf: Fix IP for relocating call depth accounting

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Message-ID: <Zfv4RGwe5+h0zNI5@gmail.com>
Date: Thu, 21 Mar 2024 10:05:08 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Joan Bruguera Micó <joanbrugueram@...il.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Uros Bizjak <ubizjak@...il.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 2/2] x86/bpf: Fix IP for relocating call depth accounting


* Joan Bruguera Micó <joanbrugueram@...il.com> wrote:

> The recently introduced support for %rip-relative relocations in the
> call thunk template assumes that the code is being patched in-place,
> so the destination of the relocation matches the address of the code.
> This is not true for the call depth accounting emitted by the BPF JIT,
> so the calculated address is wrong and usually causes a page fault.
> 
> Pass the destination IP when the BPF JIT emits call depth accounting.
> 
> Fixes: 17bce3b2ae2d ("x86/callthunks: Handle %rip-relative relocations in call thunk template")
> Signed-off-by: Joan Bruguera Micó <joanbrugueram@...il.com>
> ---
>  arch/x86/include/asm/alternative.h |  4 ++--
>  arch/x86/kernel/callthunks.c       |  4 ++--

For the generic x86 changes - I guess you want to push this upstream via 
the networking tree:

  Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo