Re: [Xen-devel] [PATCH] tests/x86emul: Annotate test blobs as executable code

[Jan Beulich <JBeulich@xxxxxxxx>]

On 02.08.2019 20:31, Andrew Cooper wrote:
> On 03/07/2019 11:47, Jan Beulich wrote:
>>>>> On 24.05.19 at 17:15, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> --- a/tools/tests/x86_emulator/Makefile
>>> +++ b/tools/tests/x86_emulator/Makefile
>>> @@ -149,7 +149,7 @@ $(addsuffix .h,$(TESTCASES)): %.h: %.c testcase.mk 
>>> Makefile
>>>             (echo 'static const unsigned int __attribute__((section(".test, 
>>> \"ax\", @progbits #")))' \
>>>                   "$${prefix}_$(arch)$${flavor}[] = {"; \
>>>              od -v -t x $*.bin | sed -e 's/^[0-9]* /0x/' -e 's/ /, 0x/g' -e 
>>> 's/$$/,/'; \
>>> -            echo "};") >>$@.new; \
>>> +            echo "}; asm(\".type $${prefix}_$(arch)$${flavor}, 
>>> STT_FUNC;\");") >>$@.new; \
>> While I think we've sufficiently agreed on future gas behavior
>> that I'd consider this change fine to make as long as you add
>> an intermediate step going through STT_NOTYPE, I'd like to note
>> that your mileage from this will only be about 50%: While the
>> 64-bit blobs will disassemble fine, I'm afraid the 32-bit ones
>> will be somewhat garbled. Sadly there's no annotation or alike
>> (like Arm's mapping symbols) that one could use to make
>> disassemblers switch bitness for separate blocks of code.
> 
> Thats fine.
> 
> Disassembling twice, once with -mi386 works well, as the symbol names
> still get emitted sensibly.  I even use -m i8086 for bits of Xen's
> trampoline.
> 
> Its rare to need to look at a different disassembly, but its very easy
> to do so if you need to.
> 
> Can I take this reply as an ack for using the STT_NOTYPE intermediate step?

Yes - sorry for not being explicit in this regard.

Jan
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