Re: [RFC PATCH 10/18] qemu: Introduce legacy_binary_is_big_endian() helper

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

On 6/3/25 08:28, Thomas Huth wrote:
> On 05/03/2025 16.39, Philippe Mathieu-Daudé wrote:
>> Introduce legacy_binary_endianness() to return the endianness
>> of a legacy binary, and legacy_binary_is_big_endian() being
>> equivalent of compile time TARGET_BIG_ENDIAN definition.
>>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>>   include/qemu/legacy_binary_info.h |  8 ++++++
>>   legacy_binary_info.c              | 43 +++++++++++++++++++++++++++++++
>>   2 files changed, 51 insertions(+)
> 
> We already have target_words_bigendian() ... why do we need yet another 
> function?

target_words_bigendian() depends on a compile time constant that we want
to get rid of: TARGET_BIG_ENDIAN.

Also, since vCPUs can be configured in different endianness, both the
method and definition are misleading, what they mean is "the *binary*
uses BIG endianness by default".
For example we can now build a TARGET_BIG_ENDIAN microblaze binary
with all vCPU core instantiated in little endianness.

Since unified binary won't have particular endianness knowledge
(still, machines will), I suggest:

target_words_bigendian() -> qemu_legacy_binary_is_bigendian()