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This patch adds the uret, sret, and mret instructions for use with
returning from user-, supervisor-, and machine-level code, respectively.
These instructions read the STATUS register to determine the previous
privilege level and modify it to re-enable interrupts at the old
privilege level. These instructions can only be executed at the
corresponding privilege level or higher.
Change-Id: I6125c31cb2fdcc3f83eca86910519e81ffbbbfc9
Reviewed-on: https://gem5-review.googlesource.com/11136
Maintainer: Alec Roelke <alec.roelke@gmail.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Robert Scheffel <robert.scheffel1@tu-dresden.de>
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RISC-V has a set of CSRs that contain information about a trap that was
taken into each privilegel level, such as illegal instruction bytes or
faulting address. This patch adds that register, modifies existing
faults to make use of it, and adds a new fault for future use with
handling page faults and bad addresses.
Change-Id: I3004bd7b907e7dc75e5f1a8452a1d74796a7a551
Reviewed-on: https://gem5-review.googlesource.com/11135
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Alec Roelke <alec.roelke@gmail.com>
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This patch adds support for handling RISC-V faults, including tracking
current and previous execution privilege, correctly switching to
the privilege mode specified by CSRs, and setting/storing the PC. It
also includes changes introduced by patch #9821, which disables
interrupts during handling of a fault.
Change-Id: Ie9c0f29719620c20783540d3bdb2db44f6114fc9
Reviewed-on: https://gem5-review.googlesource.com/9161
Maintainer: Alec Roelke <ar4jc@virginia.edu>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
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These changes enable a simple binary to be simulated in full system mode.
Additionally, a new fault was implemented.
It is executed once the CPU is initialized.
This fault clears all interrupts and sets the pc to a reset vector.
Change-Id: I50cfac91a61ba39a6ef3d38caca8794073887c88
Reviewed-on: https://gem5-review.googlesource.com/9061
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
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This patch fixes some bugs that were missed with the changes to the
decoder that enabled compatibility with compressed instructions. In
order to accommodate speculation with variable instruction widths, a few
assertions in decoder had to be changed to returning faults as the
specification describes should normally happen. The rest of these
assertions will be changed in a later patch.
[Remove commented-out debugging line and add clarifying comment to
registerName in utility.hh.]
Change-Id: I3f333008430d4a905cb59547a3513f5149b43b95
Reviewed-on: https://gem5-review.googlesource.com/4041
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Alec Roelke <ar4jc@virginia.edu>
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Third of five patches adding RISC-V to GEM5. This patch adds the RV64FD
extensions, which include single- and double-precision floating point
instructions.
Patch 1 introduced RISC-V and implemented the base instruction set, RV64I
and patch 2 implemented the integer multiply extension, RV64M.
Patch 4 will implement the atomic memory instructions, RV64A, and patch
5 will add support for timing, minor, and detailed CPU models that is
missing from the first four patches.
[Fixed exception handling in floating-point instructions to conform better
to IEEE-754 2008 standard and behavior of the Chisel-generated RISC-V
simulator.]
[Fixed style errors in decoder.isa.]
[Fixed some fuzz caused by modifying a previous patch.]
Signed-off by: Alec Roelke
Signed-off by: Jason Lowe-Power <jason@lowepower.com>
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First of five patches adding RISC-V to GEM5. This patch introduces the
base 64-bit ISA (RV64I) in src/arch/riscv for use with syscall emulation.
The multiply, floating point, and atomic memory instructions will be added
in additional patches, as well as support for more detailed CPU models.
The loader is also modified to be able to parse RISC-V ELF files, and a
"Hello world\!" example for RISC-V is added to test-progs.
Patch 2 will implement the multiply extension, RV64M; patch 3 will implement
the floating point (single- and double-precision) extensions, RV64FD;
patch 4 will implement the atomic memory instructions, RV64A, and patch 5
will add support for timing, minor, and detailed CPU models that is missing
from the first four patches (such as handling locked memory).
[Removed several unused parameters and imports from RiscvInterrupts.py,
RiscvISA.py, and RiscvSystem.py.]
[Fixed copyright information in RISC-V files copied from elsewhere that had
ARM licenses attached.]
[Reorganized instruction definitions in decoder.isa so that they are sorted
by opcode in preparation for the addition of ISA extensions M, A, F, D.]
[Fixed formatting of several files, removed some variables and
instructions that were missed when moving them to other patches, fixed
RISC-V Foundation copyright attribution, and fixed history of files
copied from other architectures using hg copy.]
[Fixed indentation of switch cases in isa.cc.]
[Reorganized syscall descriptions in linux/process.cc to remove large
number of repeated unimplemented system calls and added implmementations
to functions that have received them since it process.cc was first
created.]
[Fixed spacing for some copyright attributions.]
[Replaced the rest of the file copies using hg copy.]
[Fixed style check errors and corrected unaligned memory accesses.]
[Fix some minor formatting mistakes.]
Signed-off by: Alec Roelke
Signed-off by: Jason Lowe-Power <jason@lowepower.com>
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