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Date: Fri, 17 May 2024 18:09:42 +0200
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Subject: Re: [PATCH RESEND v8 16/16] bpf: remove CONFIG_BPF_JIT dependency on
 CONFIG_MODULES of
To: Will Deacon <will@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>, linux-kernel@vger.kernel.org,
 Alexandre Ghiti <alexghiti@rivosinc.com>,
 Andrew Morton <akpm@linux-foundation.org>, =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?=
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References: <20240505160628.2323363-1-rppt@kernel.org>
 <20240505160628.2323363-17-rppt@kernel.org>
 <7983fbbf-0127-457c-9394-8d6e4299c685@gmail.com>
 <20240517154632.GA320@willie-the-truck>
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From: Klara Modin <klarasmodin@gmail.com>
In-Reply-To: <20240517154632.GA320@willie-the-truck>
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On 2024-05-17 17:46, Will Deacon wrote:
> Hi Klara,
> 
> On Fri, May 17, 2024 at 01:00:31AM +0200, Klara Modin wrote:
>>
>> 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).
> 
> Thanks for the report. I was able to reproduce this using QEMU and it
> looks like the problem is because bpf_arch_text_copy() silently fails
> to write to the read-only area as a result of patch_map() faulting and
> the resulting -EFAULT being chucked away.
> 
> Please can you try the diff below?
> 
> Will
> 
> --->8
> 
> diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
> index 255534930368..94b9fea65aca 100644
> --- a/arch/arm64/kernel/patching.c
> +++ b/arch/arm64/kernel/patching.c
> @@ -36,7 +36,7 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>   
>          if (image)
>                  page = phys_to_page(__pa_symbol(addr));
> -       else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
> +       else if (IS_ENABLED(CONFIG_EXECMEM))
>                  page = vmalloc_to_page(addr);
>          else
>                  return addr;
> 

This seems to work from my short testing.

Thanks,
Tested-by: Klara Modin <klarasmodin@gmail.com>