Re: [PATCH 7/7] linux-user: limit check to HOST_LONG_BITS < TARGET_ABI_BITS

[Thomas Huth <thuth@redhat.com>]

On 27/05/2020 16.44, Laurent Vivier wrote:
> Le 25/05/2020 à 15:18, Thomas Huth a écrit :
>> From: Alex Bennée <alex.bennee@linaro.org>
>>
>> Newer clangs rightly spot that you can never exceed the full address
>> space of 64 bit hosts with:
>>
>>   linux-user/elfload.c:2076:41: error: result of comparison 'unsigned
>>   long' > 18446744073709551615 is always false
>>   [-Werror,-Wtautological-type-limit-compare]
>>   4685         if ((guest_hiaddr - guest_base) > ~(uintptr_t)0) {
>>   4686             ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~
>>   4687 1 error generated.
>>
>> So lets limit the check to 32 bit hosts only.
>>
>> Fixes: ee94743034bf
>> Reported-by: Thomas Huth <thuth@redhat.com>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> [thuth: Use HOST_LONG_BITS < TARGET_ABI_BITS instead of HOST_LONG_BITS == 32]
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  linux-user/elfload.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
>> index 01a9323a63..ebc663ea0b 100644
>> --- a/linux-user/elfload.c
>> +++ b/linux-user/elfload.c
>> @@ -2073,12 +2073,14 @@ static void pgb_have_guest_base(const char *image_name, abi_ulong guest_loaddr,
>>              exit(EXIT_FAILURE);
>>          }
>>      } else {
>> +#if HOST_LONG_BITS < TARGET_ABI_BITS
>>          if ((guest_hiaddr - guest_base) > ~(uintptr_t)0) {
>>              error_report("%s: requires more virtual address space "
>>                           "than the host can provide (0x%" PRIx64 ")",
>>                           image_name, (uint64_t)guest_hiaddr - guest_base);
>>              exit(EXIT_FAILURE);
>>          }
>> +#endif
>>      }
>>  
>>      /*
>>
> 
> Philippe sent the same patch:
> 
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg699796.html

Indeed, but looking more closely, he's using slightly different
locations for the #if and #endif ... not sure what's better though...?

 Thomas