Re: [Qemu-devel] [PATCH] tcg: assert last byte is in guest space

[Richard Henderson <richard.henderson@linaro.org>]

On 2/8/19 10:32 AM, Rémi Denis-Courmont wrote:
> Le perjantaina 8. helmikuuta 2019, 20.12.13 EET Richard Henderson a écrit :
>> On 2/8/19 8:37 AM, Rémi Denis-Courmont wrote:
>>> Rather than assert that the first byte of a checked range is within the
>>> guest address space, assert that the last byte is. The assertion is
>>> moved past the overflow check to ensure that the last byte is actually
>>> the one with the highest address.
>>>
>>> Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
>>> ---
>>>
>>>  accel/tcg/translate-all.c | 14 +++++++-------
>>>  1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> What are you trying to fix here?
> 
> As far as I can tell, the following code assumes that the entire range of 
> checked addresses falls within the guest address range. So it makes sense to 
> fail the assertion if the any byte is out of range, rather than only the first 
> one.

Sure.  But that would call for adding a second assert, rather than removing one
from some paths.  Which you say you "would not dare", which is confusing to me.

Is there a particular problem you are attempting to solve, or is this mere code
inspection?


r~