On 8/12/25 17:37, Eric Auger wrote:
Introduce a script that takes as input the Registers.json file
delivered in the AARCHMRS Features Model downloadable from the
Arm Developer A-Profile Architecture Exploration Tools page:
https://developer.arm.com/Architectures/A-
Profile%20Architecture#Downloads
and outputs the list of ID regs in target/arm/cpu-sysregs.h.inc
under the form of DEF(<name>, <op0>, <op1>, <crn>, <crm>, <op2>).
Great idea!
We only care about IDregs with opcodes satisfying:
op0 = 3, op1 within [0, 3], crn = 0, crm within [0, 7], op2 within [0, 7]
Signed-off-by: Eric Auger <[email protected]>
---
This was tested with https://developer.arm.com/-/cdn-downloads/
permalink/Exploration-Tools-OS-Machine-Readable-Data/AARCHMRS_BSD/
AARCHMRS_OPENSOURCE_A_profile_FAT-2025-09_ASL0.tar.gz
Discussion about undesired generated regs can be found in
https://lore.kernel.org/all/
CAFEAcA9OXi4v+hdBMamQv85HYp2EqxOA5=nfsdz5e3nf8rp...@mail.gmail.com/
---
scripts/update-aarch64-sysreg-code.py | 133 ++++++++++++++++++++++++++
1 file changed, 133 insertions(+)
create mode 100755 scripts/update-aarch64-sysreg-code.py
diff --git a/scripts/update-aarch64-sysreg-code.py b/scripts/update-
aarch64-sysreg-code.py
new file mode 100755
index 0000000000..c7b31035d1
--- /dev/null
+++ b/scripts/update-aarch64-sysreg-code.py
@@ -0,0 +1,133 @@
+#!/usr/bin/env python3
+
+# This script takes as input the Registers.json file delivered in
+# the AARCHMRS Features Model downloadable from the Arm Developer
+# A-Profile Architecture Exploration Tools page:
+# https://developer.arm.com/Architectures/A-
Profile%20Architecture#Downloads
+# and outputs the list of ID regs in target/arm/cpu-sysregs.h.inc
+# under the form of DEF(<name>, <op0>, <op1>, <crn>, <crm>, <op2>)
+#
+# Copyright (C) 2025 Red Hat, Inc.
+#
+# Authors: Eric Auger <[email protected]>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+
+import json
+import os
+import sys
+
[*]
+# returns the int value of a given @opcode for a reg @encoding
+def get_opcode(encoding, opcode):
+ fvalue = encoding.get(opcode)
+ if fvalue:
+ value = fvalue.get('value')
+ if isinstance(value, str):
+ value = value.strip("'")
+ value = int(value,2)
+ return value
+ return -1
+
+def extract_idregs_from_registers_json(filename):
+ """
+ Load a Registers.json file and extract all ID registers, decode
their
+ opcode and dump the information in target/arm/cpu-sysregs.h.inc
+
+ Args:
+ filename (str): The path to the Registers.json
+ returns:
+ idregs: list of ID regs and their encoding
+ """
+ if not os.path.exists(filename):
+ print(f"Error: {filename} could not be found!")
+ return {}
+
+ try:
+ with open(filename, 'r') as f:
+ register_data = json.load(f)
+
+ except json.JSONDecodeError:
+ print(f"Could not decode json from '{filename}'!")
+ return {}
+ except Exception as e:
+ print(f"Unexpected error while reading {filename}: {e}")
+ return {}
+
+ registers = [r for r in register_data if isinstance(r, dict) and \
+ r.get('_type') == 'Register']
+
+ idregs = {}
+
+ # Some regs have op code values like 000x, 001x. Anyway we don't
need
+ # them. Besides some regs are undesired in the generated file
such as
+ # CCSIDR_EL1 and CCSIDR2_EL1 which are arrays of regs. Also exclude
+ # VMPIDR_EL2 and VPIDR_EL2 which are outside of the IDreg scope we
+ # are interested in and are tricky to decode as their system
accessor
+ # refer to MPIDR_EL1/MIDR_EL1 respectively
+
+ skiplist = ['ALLINT', 'PM', 'S1_', 'S3_', 'SVCR', \
+ 'CCSIDR_EL1', 'CCSIDR2_EL1', 'VMPIDR_EL2', 'VPIDR_EL2']
Since we might have to update this array, I'd move it (and the big
comment preceding) in [*].
+
+ for register in registers:
+ reg_name = register.get('name')
+
+ is_skipped = any(term in (reg_name or "").upper() for term in
skiplist)
+
+ if reg_name and not is_skipped:
+ accessors = register.get('accessors', [])
+
+ for accessor in accessors:
+ type = accessor.get('_type')
+ if type in ['Accessors.SystemAccessor']:
+ encoding_list = accessor.get('encoding')
+
+ if isinstance(encoding_list, list) and
encoding_list and \
+ isinstance(encoding_list[0], dict):
+ encoding_wrapper = encoding_list[0]
+ encoding_source =
encoding_wrapper.get('encodings', \
+
encoding_wrapper)
+
+ if isinstance(encoding_source, dict):
+ op0 = get_opcode(encoding_source, 'op0')
+ op1 = get_opcode(encoding_source, 'op1')
+ op2 = get_opcode(encoding_source, 'op2')
+ crn = get_opcode(encoding_source, 'CRn')
+ crm = get_opcode(encoding_source, 'CRm')
+ encoding_str=f"{op0} {op1} {crn}
{crm} {op2}"
+
+ # ID regs are assumed within this scope
+ if op0 == 3 and (op1 == 0 or op1 == 1 or op1 == 3) and \
+ crn == 0 and (crm >= 0 and crm <= 7) and (op2 >= 0
and op2 <= 7):
+ idregs[reg_name] = encoding_str
+
+ return idregs
+
+if __name__ == "__main__":
+ # Single arg expectedr: the path to the Registers.json file
Typo "expectedr".
+ if len(sys.argv) < 2:
+ print("Usage: scripts/update-aarch64-sysreg-code.py
<path_to_registers_json>")
+ sys.exit(1)
+ else:
+ json_file_path = sys.argv[1]
+
+ extracted_registers =
extract_idregs_from_registers_json(json_file_path)
+
+ if extracted_registers:
+ output_list = extracted_registers.items()
+
+ # Sort by register name
+ sorted_output = sorted(output_list, key=lambda item: item[0])
+
+ # format lines as DEF(<name>, <op0>, <op1>, <crn>, <crm>, <op2>)
+ final_output = ""
+ for reg_name, encoding in sorted_output:
+ reformatted_encoding = encoding.replace(" ", ", ")
+ final_output += f"DEF({reg_name}, {reformatted_encoding})\n"
+
+ with open("target/arm/cpu-sysregs.h.inc", 'w') as f:
+ f.write("/* SPDX-License-Identifier: BSD-3-Clause */\n\n")
+ f.write("/* This file is autogenerated by ")
+ f.write("scripts/update-aarch64-sysreg-code.py */\n\n")
