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Subject: Re: [PATCH v4] powerpc/uprobes: Validation for prefixed instruction
To:     Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc:     mpe@ellerman.id.au, oleg@redhat.com, rostedt@goodmis.org,
        paulus@samba.org, jniethe5@gmail.com, naveen.n.rao@linux.ibm.com,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        christophe.leroy@csgroup.eu
References: <20210305115433.140769-1-ravi.bangoria@linux.ibm.com>
From:   Sandipan Das <sandipan@linux.ibm.com>
Message-ID: <fcbf618d-453e-b6ab-a41f-f69157ec1504@linux.ibm.com>
Date:   Mon, 8 Mar 2021 10:03:45 +0530
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On 05/03/21 5:24 pm, Ravi Bangoria wrote:
> As per ISA 3.1, prefixed instruction should not cross 64-byte
> boundary. So don't allow Uprobe on such prefixed instruction.
> 
> There are two ways probed instruction is changed in mapped pages.
> First, when Uprobe is activated, it searches for all the relevant
> pages and replace instruction in them. In this case, if that probe
> is on the 64-byte unaligned prefixed instruction, error out
> directly. Second, when Uprobe is already active and user maps a
> relevant page via mmap(), instruction is replaced via mmap() code
> path. But because Uprobe is invalid, entire mmap() operation can
> not be stopped. In this case just print an error and continue.
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
> Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> v3: https://lore.kernel.org/r/20210304050529.59391-1-ravi.bangoria@linux.ibm.com
> v3->v4:
>   - CONFIG_PPC64 check was not required, remove it.
>   - Use SZ_ macros instead of hardcoded numbers.
> 

Acked-by: Sandipan Das <sandipan@linux.ibm.com>