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When performing a real mode far jump, we were computing the offset into the segment more or less correctly, but then when we tried to actually set the PC using it, we used the second of the two wrip microop arguments. The first argument is an unsigned value and is intended to be a base to work from when figuring out the new IP, and the second argument is a signed offset which can be used to implement relative jumps/branches. When we used the second operand for our new value, setting the first operand to t0 (the zero register on x86), we would inadvertantly sign extend it since the wrip instruction would treat it as a signed value. Instead, we can just switch the two operands so that the wrip microop treats the desired value as the unsigned base, and then adds a signed t0 to it, which will still be 0 one way or the other. Also, while researching this bug, I found that the size used for computing the new IP is always the operand size, and never the address size. This CL fixes that problem as well by removing the faulty override. Change-Id: I96ac9effd37b40161dd8d0b634c5869e767a8873 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55243 Reviewed-by: Gabe Black <gabe.black@gmail.com> Maintainer: Gabe Black <gabe.black@gmail.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/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.