linux-kernel - Re: [PATCH RESEND v8 16/16] bpf: remove CONFIG_BPF_JIT dependency on CONFIG

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Date: Fri, 17 May 2024 01:00:31 +0200
From: Klara Modin <klarasmodin@...il.com>
To: Mike Rapoport <rppt@...nel.org>, linux-kernel@...r.kernel.org
Cc: Alexandre Ghiti <alexghiti@...osinc.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Björn Töpel
 <bjorn@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
 Christophe Leroy <christophe.leroy@...roup.eu>,
 "David S. Miller" <davem@...emloft.net>, Dinh Nguyen <dinguyen@...nel.org>,
 Donald Dutile <ddutile@...hat.com>, Eric Chanudet <echanude@...hat.com>,
 Heiko Carstens <hca@...ux.ibm.com>, Helge Deller <deller@....de>,
 Huacai Chen <chenhuacai@...nel.org>,
 Kent Overstreet <kent.overstreet@...ux.dev>, Liviu Dudau
 <liviu@...au.co.uk>, Luis Chamberlain <mcgrof@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Masami Hiramatsu <mhiramat@...nel.org>,
 Michael Ellerman <mpe@...erman.id.au>, Nadav Amit <nadav.amit@...il.com>,
 Palmer Dabbelt <palmer@...belt.com>, Peter Zijlstra <peterz@...radead.org>,
 Philippe Mathieu-Daudé <philmd@...aro.org>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Russell King <linux@...linux.org.uk>, Sam Ravnborg <sam@...nborg.org>,
 Song Liu <song@...nel.org>, Steven Rostedt <rostedt@...dmis.org>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
 Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>,
 bpf@...r.kernel.org, linux-arch@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
 linux-mm@...ck.org, linux-modules@...r.kernel.org,
 linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
 linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev,
 netdev@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH RESEND v8 16/16] bpf: remove CONFIG_BPF_JIT dependency on
 CONFIG_MODULES of

Hi,

On 2024-05-05 18:06, Mike Rapoport wrote:
> From: "Mike Rapoport (IBM)" <rppt@...nel.org>
> 
> BPF just-in-time compiler depended on CONFIG_MODULES because it used
> module_alloc() to allocate memory for the generated code.
> 
> Since code allocations are now implemented with execmem, drop dependency of
> CONFIG_BPF_JIT on CONFIG_MODULES and make it select CONFIG_EXECMEM.
> 
> Suggested-by: Björn Töpel <bjorn@...nel.org>
> Signed-off-by: Mike Rapoport (IBM) <rppt@...nel.org>
> ---
>   kernel/bpf/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
> index bc25f5098a25..f999e4e0b344 100644
> --- a/kernel/bpf/Kconfig
> +++ b/kernel/bpf/Kconfig
> @@ -43,7 +43,7 @@ config BPF_JIT
>   	bool "Enable BPF Just In Time compiler"
>   	depends on BPF
>   	depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
> -	depends on MODULES
> +	select EXECMEM
>   	help
>   	  BPF programs are normally handled by a BPF interpreter. This option
>   	  allows the kernel to generate native code when a program is loaded

This does not seem to work entirely. If build with BPF_JIT without 
module support for my Raspberry Pi 3 B I get warnings in my kernel log 
(easiest way to trigger it seems to be trying to ssh into it, which fails).

Kind regards,
Klara Modin
View attachment "bpf-jit-brk2" of type "text/plain" (10053 bytes)

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Download attachment "config.gz" of type "application/gzip" (32547 bytes)