Re: [PATCH RESEND v8 16/16] bpf: remove CONFIG_BPF_JIT dependency on CONFIG_MODULES of

Klara Modin
2024-05-17T16:09:47Z

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>