Re: [PATCH 1/2] perf/x86/intel/ds: Work around BTS leaking kernel addresses

[Alexander Shishkin]

Ingo Molnar <mingo@xxxxxxxxxx> writes:

> * Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx> wrote:
>
>> +	for (at = base; at < top; at++) {
>> +		/*
>> +		 * Note that right now *this* BTS code only works if
>> +		 * attr::exclude_kernel is set, but let's keep this extra
>> +		 * check here in case that changes.
>> +		 */
>> +		if (event->attr.exclude_kernel &&
>> +		    (at->from >= PAGE_OFFSET || at->to >= PAGE_OFFSET))
>> +			skip++;
>
> Yeah, so that only works on 32-bit kernels, on 64-bit kernels the check for kernel 
> addresses is to see whether it's a negative address. PAGE_OFFSET points to above 
> any hypervisor's address, so even with your fix we could still leak hypervisor 
> addresses.
>
> I.e. use the kernel_ip() primitive instead.

That's what I've been looking for, thanks!

Regards,
--
Alex
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/