Re: [PATCH 7/9] MIPS: uprobes: Flush icache via kernel address

[Ralf Baechle <ralf@linux-mips.org>]

On Thu, Sep 01, 2016 at 05:30:13PM +0100, James Hogan wrote:

> Update arch_uprobe_copy_ixol() to use the kmap_atomic() based kernel
> address to flush the icache with flush_icache_range(), rather than the
> user mapping. We have the kernel mapping available anyway and this
> avoids having to switch to using the new __flush_icache_user_range() for
> the sake of Enhanced Virtual Addressing (EVA) where flush_icache_range()
> will become ineffective on user addresses.
> 
> Signed-off-by: James Hogan <james.hogan@imgtec.com>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
> Cc: linux-mips@linux-mips.org
> ---
>  arch/mips/kernel/uprobes.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/mips/kernel/uprobes.c b/arch/mips/kernel/uprobes.c
> index 8452d933a645..9a507ab1ea38 100644
> --- a/arch/mips/kernel/uprobes.c
> +++ b/arch/mips/kernel/uprobes.c
> @@ -301,19 +301,14 @@ int set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
>  void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
>  				  void *src, unsigned long len)
>  {
> -	void *kaddr;
> +	void *kaddr, kstart;
>  
>  	/* Initialize the slot */
>  	kaddr = kmap_atomic(page);
> -	memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
> +	kstart = kaddr + (vaddr & ~PAGE_MASK);
> +	memcpy(kstart, src, len);
> +	flush_icache_range(kstart, kstart + len);
>  	kunmap_atomic(kaddr);
> -
> -	/*
> -	 * The MIPS version of flush_icache_range will operate safely on
> -	 * user space addresses and more importantly, it doesn't require a
> -	 * VMA argument.
> -	 */
> -	flush_icache_range(vaddr, vaddr + len);

I can't convince myself this is right wrt. to cache aliases ...

  Ralf