linux-kernel - Re: [PATCH] arm64: uprobes: Optimize cache flushes for xol slot

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Message-ID: <20240919141824.GB12149@redhat.com>
Date: Thu, 19 Sep 2024 16:18:25 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Liao Chang <liaochang1@...wei.com>
Cc: mhiramat@...nel.org, peterz@...radead.org, catalin.marinas@....com,
	will@...nel.org, mark.rutland@....com, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64: uprobes: Optimize cache flushes for xol slot

On 09/19, Liao Chang wrote:
>
> --- a/arch/arm64/kernel/probes/uprobes.c
> +++ b/arch/arm64/kernel/probes/uprobes.c
> @@ -17,12 +17,16 @@ void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
>  	void *xol_page_kaddr = kmap_atomic(page);
>  	void *dst = xol_page_kaddr + (vaddr & ~PAGE_MASK);
>
> +	if (!memcmp(dst, src, len))
> +		goto done;

can't really comment, I know nothing about arm64...

but don't we need to change __create_xol_area()

	-	area->page = alloc_page(GFP_HIGHUSER);
	+	area->page = alloc_page(GFP_HIGHUSER | __GFP_ZERO);

to avoid the false positives?

Oleg.