abi.h

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/*
 * Copyright 2025 dogtopus
 * SPDX-License-Identifier: MIT
 */
 
#ifndef __OSDEP_ABI_H__
#define __OSDEP_ABI_H__
 
#if defined(__clang__)
 
// clang: Ignore unused parameter warning and clangd's warning on asm().
#define NO_EXPECTED_WARNINGS_BEGIN \
    _Pragma("clang diagnostic push") \
    _Pragma("clang diagnostic ignored \"-Wunused-parameter\"") \
    _Pragma("clang diagnostic ignored \"-Wlanguage-extension-token\"")
#define NO_EXPECTED_WARNINGS_END \
    _Pragma("clang diagnostic pop")
 
#elif defined(__GNUC__)  // !defined(__clang__)
 
// gcc: Ignore unused parameter warning.
#define NO_EXPECTED_WARNINGS_BEGIN \
    _Pragma("GCC diagnostic push") \
    _Pragma("GCC diagnostic ignored \"-Wunused-parameter\"")
#define NO_EXPECTED_WARNINGS_END \
    _Pragma("GCC diagnostic pop")
 
#else  // !defined(__GNUC__)
 
// No-op
#define NO_EXPECTED_WARNINGS_BEGIN
#define NO_EXPECTED_WARNINGS_END
 
#endif  // defined(__clang__) || defined(__GNUC__)
 
#define __APCS_WRAPPER_BASE(NAME, VA_LIST_NAME, STATIC, RETTYPE, ...) \
    NO_EXPECTED_WARNINGS_BEGIN \
    __attribute__((naked)) STATIC RETTYPE NAME(__VA_ARGS__) { \
        asm ( \
            /* x x x x | a0 a1 a2 a3 ... */ \
            "push {r0-r3}\n\t" \
            /* x x x x | <lr> a0 a1 a2 a3 ... */ \
            "push {lr}\n\t" \
            /* &a0 x x x | <lr> a0 a1 a2 a3 ... */ \
            "add r0, sp, #4\n\t" \
            /* &a0 x &<lr> x | <lr> a0 a1 a2 a3 ... */ \
            "mov r2, sp\n\t" \
            "tst r2, #7\n\t" \
            /* &a0 x flag x | [padding] <lr> a0 a1 a2 a3 ... */ \
            "mov r2, #0\n\t" \
            "subeq sp, sp, #4\n\t" \
            "moveq r2, #1\n\t" \
            /* &a0 x x x | flag [padding] <lr> a0 a1 a2 a3 ... */ \
            "push {r2}\n\t" \
            "bl __osdep_apcs_thunk_"#NAME "\n\t" \
            /* ret ret_hi flag x | [padding] <lr> a0 a1 a2 a3 ... */ \
            "pop {r2}\n\t" \
            "cmp r2, #0\n\t" \
            /* ret ret_hi flag x | <lr> a0 a1 a2 a3 ... */ \
            "addne sp, sp, #4\n\t" \
            /* ret ret_hi <lr> x | a0 a1 a2 a3 ... */ \
            "pop {r2}\n\t" \
            /* ret ret_hi <lr> x | ... */ \
            "add sp, sp, #16\n\t" \
            "bx r2" \
        ); \
    } \
    NO_EXPECTED_WARNINGS_END \
    __attribute__((used)) static RETTYPE __osdep_apcs_thunk_##NAME(va_list VA_LIST_NAME)
 
#define APCS_WRAPPER(NAME, VA_LIST_NAME, RETTYPE, ...) \
    __APCS_WRAPPER_BASE(NAME, VA_LIST_NAME, , RETTYPE, __VA_ARGS__)
 
#define APCS_WRAPPER_STATIC(NAME, VA_LIST_NAME, RETTYPE, ...) \
    __APCS_WRAPPER_BASE(NAME, VA_LIST_NAME, static, RETTYPE, __VA_ARGS__)
 
#endif  // __OSDEP_ABI_H__