Re: [PATCH for-8.0 v2 10/12] linux-user: Pass last not end to probe_guest_base

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 28/3/23 19:47, Richard Henderson wrote:
> On 3/28/23 06:51, Philippe Mathieu-Daudé wrote:
>> Hi Richard,
>>
>> On 27/3/23 23:18, Richard Henderson wrote:
>>> Pass the address of the last byte of the image, rather than
>>> the first address past the last byte.  This avoids overflow
>>> when the last page of the address space is involved.
>>>
>>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>> ---
>>>   linux-user/elfload.c  | 24 ++++++++++++------------
>>>   linux-user/flatload.c |  2 +-
>>>   2 files changed, 13 insertions(+), 13 deletions(-)


>>> index e99570ca18..5efec2630e 100644
>>> --- a/linux-user/flatload.c
>>> +++ b/linux-user/flatload.c
>>> @@ -448,7 +448,7 @@ static int load_flat_file(struct linux_binprm * 
>>> bprm,
>>>        * Allocate the address space.
>>>        */
>>>       probe_guest_base(bprm->filename, 0,
>>> -                     text_len + data_len + extra + indx_len);
>>> +                     text_len + data_len + extra + indx_len - 1);
>>
>> Per linux-user/user-internals.h:
>>
>> /**
>>   * probe_guest_base:
>>   * @image_name: the executable being loaded
>>   * @loaddr: the lowest fixed address in the executable
>>   * @hiaddr: the highest fixed address in the executable
>>   *
>>   * Creates the initial guest address space in the host memory space.
>>   *
>>   * If @loaddr == 0, then no address in the executable is fixed,
>>   * i.e. it is fully relocatable.  In that case @hiaddr is the size
>>   * of the executable.
>>   *
>>   * This function will not return if a valid value for guest_base
>>   * cannot be chosen.  On return, the executable loader can expect
>>   *
>>   *    target_mmap(loaddr, hiaddr - loaddr, ...)
>>   *
>>   * to succeed.
>>   */
>>
>> Since here @loaddr == 0, "@hiaddr is the size of the executable",
>> not "the first address past the last byte".
>>
>> So we can not "Pass the address of the last byte of the image"
>> to this API. Maybe the API description is incorrect, in that
>> case your patch is right. Otherwise we might need to tune
>> probe_guest_base().
> 
> I'll update the documentation.

Then:

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>