Re: [PATCH 1/3] scripts: introduce scripts/update-aarch64-sysreg-code.py

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

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 <eric.auger@redhat.com>
> 
> ---
> 
> 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_pw@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 <eric.auger@redhat.com>
> +#
> +# 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")
> +            f.write(final_output)
> +        print(f"updated target/arm/cpu-sysregs.h.inc")

Fixed string (no formating) so no need for f- prefix.

Patch LGTM but it should have some unit test.