Hi Gabe,
I don't have the broken build in front of me, and it's possible it is
because I'm running on an Ubuntu 16 machine, but I had to add c+11 per the
error message I got when debugging this. If c++14 works though, great.
Thanks for the updated info -- I built the tutorial out of the old one, so
next time I'll make sure to update it accordingly.
Thanks,
Matt
On Mon, Nov 9, 2020 at 5:44 PM Gabe Black via gem5-users <
gem5-users@gem5.org> wrote:
> BTW, I do think I need to explicitly set the c++ version in the scons
> file, like in Matt's original email above. I'd probably set it to c++14
> though, to be consistent with gem5 proper. I think that will likely fix a
> build issue Bobby had with an older (7.x I think) version of gcc, where the
> default version is probably different from the compiler I'm using (10.x I
> think).
>
> Gabe
>
> On Mon, Nov 9, 2020 at 1:50 PM Gabe Black <gabe.bl...@gmail.com> wrote:
>
>> Hi folks. If you're using the magic address based version of the gem5
>> ops, then you should call, for instance, m5_exit_addr and not just m5_exit.
>> The "normal" functions are now always the magic instructions which
>> essentially only gem5 CPU models know how to execute. All call mechanisms
>> are built into the library at once now so you can use the same binary on
>> the KVM CPU, native gem5 CPUs, etc.
>>
>> You also should not change the scons files when you build. The old
>> Makefile based setup required tinkering with things to get the build you
>> wanted, but that is no longer necessary. If you need to, that's a bug and
>> we should look into it. The lines you're commenting out just set the
>> default magic address, and that's only there for legacy reasons. You can
>> set the address to use from the command line if you're using the m5
>> utility, or by setting the m5op_addr variable if using the library. You
>> still have to run map_m5_mem to make the magic physical address visible to
>> userspace for the library to work, or otherwise set up a virtual to
>> physical mapping if you were, for instance, running in the kernel which
>> somebody was doing recently.
>>
>> If you try to use a call mechanism that isn't supported by your CPU
>> model, then the behavior will be unpredictable. For x86 on the KVM CPU for
>> example, the special gem5 instructions will do whatever they look like they
>> should do on real hardware. That may be a nop, it may be to generate an
>> undefined instruction exception, etc. If it's a nop, it will just leave
>> whatever is in RAX in RAX.
>>
>> Also, argument values and return values are now handled by a layer which
>> knows and applies the actual ABI rules for a given ISA and for the specific
>> types of the arguments and return value. There should be no reason to
>> change the code which is calling the pseudo instruction to explicitly set
>> RAX, especially if you're using the address based calling mechanism which
>> doesn't go through that path at all.
>>
>> Gabe
>>
>> On Mon, Nov 9, 2020 at 1:06 PM Matt Sinclair via gem5-users <
>> gem5-users@gem5.org> wrote:
>>
>>> Hi Dan,
>>>
>>> My comment was just a general comment on the m5ops -- I thought you were
>>> using the "old" format for building m5ops and that might have been the
>>> problem. Sounds like it wasn't.
>>>
>>> I think pushing a fix to develop and tagging Gabe and Jason as reviewers
>>> is probably the right strategy.
>>>
>>> Thanks,
>>> Matt
>>>
>>> On Mon, Nov 9, 2020 at 2:33 PM Daniel Gerzhoy <daniel.gerz...@gmail.com>
>>> wrote:
>>>
>>>> I found the issue and fixed it.
>>>>
>>>> The return value wasn't being put into the Rax register in
>>>> src/arch/x86/isa/decoder/two_byte_opcodes.isa
>>>>
>>>> 0x4: BasicOperate::gem5Op({{
>>>> uint64_t ret;
>>>> bool recognized =
>>>> PseudoInst::pseudoInst<X86PseudoInstABI>(
>>>> xc->tcBase(), IMMEDIATE, ret);
>>>> if (!recognized)
>>>> fault = std::make_shared<InvalidOpcode>();
>>>> Rax = ret;
>>>>
>>>> //<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<Added This
>>>> }}, IsNonSpeculative);
>>>>
>>>> This code was simplified with the new abi stuff and the Rax = ret;
>>>> must have been lost in the shuffle.
>>>>
>>>> I could push the fix to develop, or should I just make an issue on Jira?
>>>>
>>>> Best,
>>>>
>>>> Dan
>>>>
>>>> On Mon, Nov 9, 2020 at 2:50 PM Daniel Gerzhoy <daniel.gerz...@gmail.com>
>>>> wrote:
>>>>
>>>>> Let me further say that I know that the magic instructions are being
>>>>> called. I am just getting bogus return values.
>>>>>
>>>>> On Mon, Nov 9, 2020 at 2:18 PM Daniel Gerzhoy <
>>>>> daniel.gerz...@gmail.com> wrote:
>>>>>
>>>>>> Hi Matt,
>>>>>>
>>>>>> Thanks for this, it's very helpful. However after following the
>>>>>> instructions (I had to extrapolate a little because of the directory
>>>>>> structure changes you mentioned) I get the same result: Nill returns from
>>>>>> the magic instructions.
>>>>>> Actually It isn't nill, but a constant no matter what. If I compile
>>>>>> my program with -O0 its nill, if with -O2 its: 4198192, which is
>>>>>> suspicious.
>>>>>>
>>>>>> To clarify, are these updated instructions specifically meant to fix
>>>>>> this issue I am running into? Or just general instructions to build
>>>>>> m5op.o
>>>>>>
>>>>>> Here are the specific changes I made according to the link you
>>>>>> provided, the supplemental instructions, and extrapolating based on the
>>>>>> directory structure change.
>>>>>>
>>>>>> 1. In SConsopts I commented both:
>>>>>>
>>>>>> --- a/util/m5/src/abi/x86/SConsopts
>>>>>> +++ b/util/m5/src/abi/x86/SConsopts
>>>>>> @@ -27,8 +27,8 @@ Import('*')
>>>>>>
>>>>>> env['ABI'] = 'x86'
>>>>>> get_abi_opt('CROSS_COMPILE', '')
>>>>>> -env.Append(CXXFLAGS='-DM5OP_ADDR=0xFFFF0000')
>>>>>> -env.Append(CCFLAGS='-DM5OP_ADDR=0xFFFF0000')
>>>>>> +#env.Append(CXXFLAGS='-DM5OP_ADDR=0xFFFF0000')
>>>>>> +#env.Append(CCFLAGS='-DM5OP_ADDR=0xFFFF0000')
>>>>>>
>>>>>> env['CALL_TYPE']['inst'].impl('m5op.S', 'verify_inst.cc')
>>>>>> env['CALL_TYPE']['addr'].impl('m5op_addr.S', default=True)
>>>>>>
>>>>>> 2. In SConstruct I added:
>>>>>>
>>>>>> --- a/util/m5/SConstruct
>>>>>> +++ b/util/m5/SConstruct
>>>>>> @@ -44,7 +44,9 @@ def abspath(d):
>>>>>>
>>>>>> # Universal settings.
>>>>>> main.Append(CXXFLAGS=[ '-O2' ])
>>>>>> +main.Append(CXXFLAGS=[ '-std=c++11' ])
>>>>>> main.Append(CCFLAGS=[ '-O2' ])
>>>>>> main.Append(CPPPATH=[ common_include ])
>>>>>>
>>>>>> The compilation process compiles m5op.S with gcc though, so c++11
>>>>>> doesn't have any effect on it. Not sure if that matters.
>>>>>>
>>>>>> 3. Finally I linked both m5_mmap.o and m5op.o as per the instructions
>>>>>> but I am a little wary of m5_mmap
>>>>>>
>>>>>> What does m5_mmap actually do if I don't have M5OP_ADDR defined. It
>>>>>> looks like nothing? Do I need to link it?
>>>>>>
>>>>>> *Is there something inside the program I need to do before calling
>>>>>> magic instructions that has to do with m5_mmap?*
>>>>>>
>>>>>> Thanks for your help,
>>>>>>
>>>>>> Dan
>>>>>>
>>>>>> On Mon, Nov 9, 2020 at 12:12 PM Matt Sinclair <
>>>>>> mattdsincl...@gmail.com> wrote:
>>>>>>
>>>>>>> Hi Dan,
>>>>>>>
>>>>>>> In recent weeks, Gabe (if I recall correctly) updated how the m5ops
>>>>>>> are created. I had created a homework assignment for my course about
>>>>>>> it:
>>>>>>> https://pages.cs.wisc.edu/~sinclair/courses/cs752/fall2020/handouts/hw3.html
>>>>>>> (see #2), but this is now already out of date as the location of some
>>>>>>> files
>>>>>>> changed. The updated instructions are:
>>>>>>>
>>>>>>> 1. Update $GEM5_ROOT/util/m5/SConstruct, add a new line between the
>>>>>>> current lines 46 and 47:
>>>>>>>
>>>>>>> main.Append(CXXFLAGS=[ '-O2' ])
>>>>>>> *+main.Append(CXXFLAGS=[ '-std=c++11' ])*
>>>>>>>
>>>>>>> main.Append(CCFLAGS=[ '-O2' ])
>>>>>>>
>>>>>>> 2. Now run the same command you ran in step 2 of the above link:
>>>>>>>
>>>>>>> scons build/x86/out/m5
>>>>>>>
>>>>>>> 3. This will create the same two .o files in step 2 of the above
>>>>>>> link, in the same places (although the location of m5op.o may have
>>>>>>> changed to include/gem5 util/m5/build/x86/abi/x86/ according to
>>>>>>> some of the students in my course).
>>>>>>> Matt
>>>>>>>
>>>>>>> On Mon, Nov 9, 2020 at 9:25 AM Daniel Gerzhoy via gem5-users <
>>>>>>> gem5-users@gem5.org> wrote:
>>>>>>>
>>>>>>>> Hey all,
>>>>>>>>
>>>>>>>> I've recently updated to using the dev branch for my GCN3
>>>>>>>> simulations. I've noticed that I am now getting return values of 0 for
>>>>>>>> every magic instruction (m5_rpns for instance).
>>>>>>>>
>>>>>>>> Is there a special way I need to be compiling/linking m5ops.S to
>>>>>>>> get the return values to show up correctly? Or might this be a bug?
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Dan
>>>>>>>> _______________________________________________
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