linux-kernel - Re: [PATCH 2/3] arm64: use PAGE_KERNEL_ROX directly in alloc_insn_page

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Message-ID: <CAMj1kXH985Aqma47yf96N45CYkTGePVpvihrc_TmOAp2f0vN-g@mail.gmail.com>
Date:   Sat, 27 Jun 2020 09:34:42 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-hyperv@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        X86 ML <x86@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org, Jessica Yu <jeyu@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/3] arm64: use PAGE_KERNEL_ROX directly in alloc_insn_page

On Thu, 18 Jun 2020 at 08:44, Christoph Hellwig <hch@....de> wrote:
>
> Use PAGE_KERNEL_ROX directly instead of allocating RWX and setting the
> page read-only just after the allocation.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  arch/arm64/kernel/probes/kprobes.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
> index d1c95dcf1d7833..cbe49cd117cfec 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -120,15 +120,9 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>
>  void *alloc_insn_page(void)
>  {
> -       void *page;
> -
> -       page = vmalloc_exec(PAGE_SIZE);
> -       if (page) {
> -               set_memory_ro((unsigned long)page, 1);
> -               set_vm_flush_reset_perms(page);
> -       }
> -
> -       return page;
> +       return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
> +                       GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
> +                       NUMA_NO_NODE, __func__);

Why is this passing a string for the 'caller' argument, and not the
address of the caller?

>  }
>
>  /* arm kprobe: install breakpoint in text */
> --
> 2.26.2
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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