5df52e0dca
The stack size is something that applies to addresses when performing accesses as part of some instructions. This was handled inconsistently or incompletely or simply incorrectly in a few ways. First, when pushing or popping from the stack, the *address size* should be set to the stack size. The data size is generally the operand size. When the stack pointer is incremented/decremented, it should be changed by the data size. When a stack pointer is manipulated, the data size for those calculations should be the stack size. Importantly that does not change the value of the increment/decrement, which is the operand size still. This usage has been fixed throughout. The TLB generally needs to know what the address size was in order to figure out what segment offset was used so that it can do limit checks. There is some inherent inaccuracy in doing things in reverse like this, but that's how it works currently. To find that size, the TLB tried to start from first principles to figure out what the default address size was, and then whether there was an override was passed in through the request flags. This is *very* inaccurate for a few reasons. First, the override doesn't always apply. Second, the address size used by a particular instruction doesn't have to be based on any particular size, whether that is the default or alternate address size, the stack size, etc. Instead, the instructions now pass the actual size being used in as a 2 bit value (0 -> 1 byte, 1 -> 2 bytes, 2 -> 4 bytes, 3 -> 8 bytes), avoiding most of the inaccuracy and approximation. Because the CPU won't embed any size information into fetches, we'll just assume those have no wrap around within the address size. Finally, there were microops that had been added which overrode the address size to be the stack size internally, and try to help the TLB figure out what to do to figure out the address size. Because both of those things are now handled in a different way, those microops are no longer needed or used and have been deleted. Change-Id: I2b1bdf1acf1540bf643fac6d49fe1a5a576ba5c1 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55443 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Gabe Black <gabe.black@gmail.com> Reviewed-by: Gabe Black <gabe.black@gmail.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/about, and for more information about building the simulator and getting started please see http://www.gem5.org/documentation and http://www.gem5.org/documentation/learning_gem5/introduction. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/documentation/general_docs/building for more details concerning the minimum versions of these tools. Once you have all dependencies resolved, type 'scons build/<CONFIG>/gem5.opt' where CONFIG is one of the options in build_opts like ARM, NULL, MIPS, POWER, SPARC, X86, Garnet_standalone, etc. This will build an optimized version of the gem5 binary (gem5.opt) with the the specified configuration. See http://www.gem5.org/documentation/general_docs/building for more details and options. The main source tree includes these subdirectories: - build_opts: pre-made default configurations for gem5 - build_tools: tools used internally by gem5's build process. - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - include: include files for use in other programs - site_scons: modular components of the build system - 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 may need compiled system firmware, kernel binaries and one or more disk images, depending on gem5's configuration and what type of workload you're trying to run. Many of those resources can be downloaded from http://resources.gem5.org, and/or from the git repository here: https://gem5.googlesource.com/public/gem5-resources/ If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.