scripts/gen_syscall_header.py

#!/usr/bin/env python3
#
# Copyright (c) 2017 Intel Corporation
#
# SPDX-License-Identifier: Apache-2.0

import sys
from enum import Enum


class Retval(Enum):
    VOID = 0
    U32 = 1
    U64 = 2


def gen_macro(ret, argc):
    if ret == Retval.VOID:
        suffix = "_VOID"
    elif ret == Retval.U64:
        suffix = "_RET64"
    else:
        suffix = ""

    sys.stdout.write("K_SYSCALL_DECLARE%d%s(id, name" % (argc, suffix))
    if (ret != Retval.VOID):
        sys.stdout.write(", ret")
    for i in range(argc):
        sys.stdout.write(", t%d, p%d" % (i, i))
    sys.stdout.write(")")


def gen_fn(ret, argc, name, extern=False):
    sys.stdout.write("\t%s %s %s(" %
                     (("extern" if extern else "static inline"),
                      ("ret" if ret != Retval.VOID else "void"), name))
    if argc == 0:
        sys.stdout.write("void")
    else:
        for i in range(argc):
            sys.stdout.write("t%d p%d" % (i, i))
            if i != (argc - 1):
                sys.stdout.write(", ")
    sys.stdout.write(")")


def tabs(count):
    sys.stdout.write("\t" * count)


def gen_make_syscall(ret, argc, tabcount):
    tabs(tabcount)

    # The core kernel is built with the --no-whole-archive linker option.
    # For all the individual .o files which make up the kernel, if there
    # are no external references to symbols within these object files,
    # everything in the object file is dropped.
    #
    # This has a subtle interaction with system call handlers. If an object
    # file has system call handler inside it, and nothing else in the
    # object file is referenced, then the linker will prefer the weak
    # version of the handler in the generated syscall_dispatch.c. The
    # user will get an "unimplemented system call" error if the associated
    # system call for that handler is made.
    #
    # Fix this by making a fake reference to the handler function at the
    # system call site. The address gets stored inside a special section
    # "hndlr_ref".  This is enough to prevent the handlers from being
    # dropped, and the hndlr_ref section is itself dropped from the binary
    # from gc-sections; these references will not consume space.

    sys.stdout.write(
        "static _GENERIC_SECTION(hndlr_ref) __used void *href = (void *)&_handler_##name; \\\n")
    tabs(tabcount)
    if (ret != Retval.VOID):
        sys.stdout.write("return (ret)")
    if (argc <= 6 and ret != Retval.U64):
        sys.stdout.write("_arch")
    sys.stdout.write("_syscall%s_invoke%d(" %
                     (("_ret64" if ret == Retval.U64 else ""), argc))
    for i in range(argc):
        sys.stdout.write("(u32_t)p%d, " % (i))
    sys.stdout.write("id); \\\n")


def gen_call_impl(ret, argc):
    if (ret != Retval.VOID):
        sys.stdout.write("return ")
    sys.stdout.write("_impl_##name(")
    for i in range(argc):
        sys.stdout.write("p%d" % (i))
        if i != (argc - 1):
            sys.stdout.write(", ")
    sys.stdout.write("); \\\n")


def newline():
    sys.stdout.write(" \\\n")


def gen_defines_inner(ret, argc, kernel_only=False, user_only=False):
    sys.stdout.write("#define ")
    gen_macro(ret, argc)
    newline()

    if not user_only:
        gen_fn(ret, argc, "_impl_##name", extern=True)
        sys.stdout.write(";")
        newline()

    gen_fn(ret, argc, "name")
    newline()
    sys.stdout.write("\t{")
    newline()

    if kernel_only:
        sys.stdout.write("\t\t")
        gen_call_impl(ret, argc)
    elif user_only:
        gen_make_syscall(ret, argc, 2)
    else:
        sys.stdout.write("\t\tif (_is_user_context()) {")
        newline()

        gen_make_syscall(ret, argc, 3)

        sys.stdout.write("\t\t} else {")
        newline()

        # Prevent memory access issues if the implementation function gets
        # inlined
        sys.stdout.write("\t\t\tcompiler_barrier();")
        newline()

        sys.stdout.write("\t\t\t")
        gen_call_impl(ret, argc)
        sys.stdout.write("\t\t}")
        newline()

    sys.stdout.write("\t}\n\n")


def gen_defines(argc, kernel_only=False, user_only=False):
    gen_defines_inner(Retval.VOID, argc, kernel_only, user_only)
    gen_defines_inner(Retval.U32, argc, kernel_only, user_only)
    gen_defines_inner(Retval.U64, argc, kernel_only, user_only)


sys.stdout.write(
    "/* Auto-generated by gen_syscall_header.py, do not edit! */\n\n")
sys.stdout.write("#ifndef GEN_SYSCALL_H\n#define GEN_SYSCALL_H\n\n")
sys.stdout.write("#include <syscall.h>\n")

for i in range(11):
    sys.stdout.write(
        "#if !defined(CONFIG_USERSPACE) || defined(__ZEPHYR_SUPERVISOR__)\n")
    gen_defines(i, kernel_only=True)
    sys.stdout.write("#elif defined(__ZEPHYR_USER__)\n")
    gen_defines(i, user_only=True)
    sys.stdout.write("#else /* mixed kernel/user macros */\n")
    gen_defines(i)
    sys.stdout.write("#endif /* mixed kernel/user macros */\n\n")

sys.stdout.write("#endif /* GEN_SYSCALL_H */\n")