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This will let a function called with a GuestABI emulate the ... mechanism available in C. To make that possible without the functions knowing anything about the ABI and to follow C++'s (sensible) templating and virtual function rules, you have to tell VarArgs what types you might want to extract from it, unlike the pure ... varargs style mechanism. Also unlike ..., there is no mechanism in place to force the varargs to appear last in the argument list. It will pick up the progress through the arguments at the point it's reached, and will ignore any later arguments. It would be possible to be more rigorous about this by changing the callFrom templates, but the overhead in complexity is probably not worth it. Also, retrieving arguments through a VarArgs happens live, meaning at the point that the argument is asked for. If the ThreadContext or memory the argument lives in is modified before that point, the retrieved value will reflect that modification and not what the function was originally called with. Care should be taken so that this doesn't cause corrupted arguments. Finally, this mechansim (and the Guest ABI mechanism in general) is complex and should have tests written for it. That should be possible since ThreadContext is forward declared and so the test can say it works however it wants or even ignore it completely. If that changes in the future, we may need a mock ThreadContext implementation. Jira Issue: https://gem5.atlassian.net/browse/GEM5-187 Change-Id: I37484b50a3e8c0d259d9590e32fecbb5f76670c1 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23195 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu> Maintainer: Gabe Black <gabeblack@google.com> Tested-by: kokoro <noreply+kokoro@google.com>
This is the gem5 simulator. The main website can be found at http://www.gem5.org A good starting point is http://www.gem5.org/Introduction, and for more information about building the simulator and getting started please see http://www.gem5.org/Documentation and http://www.gem5.org/Tutorials. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, SWIG, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/Dependencies for more details concerning the minimum versions of the aforementioned tools. Once you have all dependencies resolved, type 'scons build/<ARCH>/gem5.opt' where ARCH is one of ALPHA, ARM, NULL, MIPS, POWER, SPARC, or X86. This will build an optimized version of the gem5 binary (gem5.opt) for the the specified architecture. See http://www.gem5.org/Build_System for more details and options. With the simulator built, have a look at http://www.gem5.org/Running_gem5 for more information on how to use gem5. The basic source release includes these subdirectories: - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - src: source code of the gem5 simulator - system: source for some optional system software for simulated systems - tests: regression tests - util: useful utility programs and files To run full-system simulations, you will need compiled system firmware (console and PALcode for Alpha), kernel binaries and one or more disk images. Please see the gem5 download page for these items at http://www.gem5.org/Download If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.