syscall.h

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/*
 * Copyright (c) 2020 BayLibre, SAS
 *
 * SPDX-License-Identifier: Apache-2.0
 */
 
#ifndef ZEPHYR_INCLUDE_ARCH_RISCV_SYSCALL_H_
#define ZEPHYR_INCLUDE_ARCH_RISCV_SYSCALL_H_
 
/*
 * Privileged mode system calls
 */
#define RV_ECALL_RUNTIME_EXCEPT         0
#define RV_ECALL_IRQ_OFFLOAD            1
 
#ifndef _ASMLANGUAGE
 
#include <zephyr/types.h>
#include <stdbool.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
/*
 * Syscall invocation macros. riscv-specific machine constraints used to ensure
 * args land in the proper registers.
 */
static inline uintptr_t arch_syscall_invoke6(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t arg3, uintptr_t arg4,
                                             uintptr_t arg5, uintptr_t arg6,
                                             uintptr_t call_id)
{
        register ulong_t a0 __asm__ ("a0") = arg1;
        register ulong_t a1 __asm__ ("a1") = arg2;
        register ulong_t a2 __asm__ ("a2") = arg3;
        register ulong_t a3 __asm__ ("a3") = arg4;
        register ulong_t a4 __asm__ ("a4") = arg5;
        register ulong_t a5 __asm__ ("a5") = arg6;
        register ulong_t a7 __asm__ ("a7") = call_id;
 
        __asm__ volatile ("ecall"
                          : "+r" (a0)
                          : "r" (a1), "r" (a2), "r" (a3), "r" (a4), "r" (a5),
                          "r" (a7)
                          : "memory");
        return a0;
}
 
static inline uintptr_t arch_syscall_invoke5(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t arg3, uintptr_t arg4,
                                             uintptr_t arg5,
                                             uintptr_t call_id)
{
        register ulong_t a0 __asm__ ("a0") = arg1;
        register ulong_t a1 __asm__ ("a1") = arg2;
        register ulong_t a2 __asm__ ("a2") = arg3;
        register ulong_t a3 __asm__ ("a3") = arg4;
        register ulong_t a4 __asm__ ("a4") = arg5;
        register ulong_t a7 __asm__ ("a7") = call_id;
 
        __asm__ volatile ("ecall"
                          : "+r" (a0)
                          : "r" (a1), "r" (a2), "r" (a3), "r" (a4), "r" (a7)
                          : "memory");
        return a0;
}
 
static inline uintptr_t arch_syscall_invoke4(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t arg3, uintptr_t arg4,
                                             uintptr_t call_id)
{
        register ulong_t a0 __asm__ ("a0") = arg1;
        register ulong_t a1 __asm__ ("a1") = arg2;
        register ulong_t a2 __asm__ ("a2") = arg3;
        register ulong_t a3 __asm__ ("a3") = arg4;
        register ulong_t a7 __asm__ ("a7") = call_id;
 
        __asm__ volatile ("ecall"
                          : "+r" (a0)
                          : "r" (a1), "r" (a2), "r" (a3), "r" (a7)
                          : "memory");
        return a0;
}
 
static inline uintptr_t arch_syscall_invoke3(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t arg3,
                                             uintptr_t call_id)
{
        register ulong_t a0 __asm__ ("a0") = arg1;
        register ulong_t a1 __asm__ ("a1") = arg2;
        register ulong_t a2 __asm__ ("a2") = arg3;
        register ulong_t a7 __asm__ ("a7") = call_id;
 
        __asm__ volatile ("ecall"
                          : "+r" (a0)
                          : "r" (a1), "r" (a2), "r" (a7)
                          : "memory");
        return a0;
}
 
static inline uintptr_t arch_syscall_invoke2(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t call_id)
{
        register ulong_t a0 __asm__ ("a0") = arg1;
        register ulong_t a1 __asm__ ("a1") = arg2;
        register ulong_t a7 __asm__ ("a7") = call_id;
 
        __asm__ volatile ("ecall"
                          : "+r" (a0)
                          : "r" (a1), "r" (a7)
                          : "memory");
        return a0;
}
 
static inline uintptr_t arch_syscall_invoke1(uintptr_t arg1, uintptr_t call_id)
{
        register ulong_t a0 __asm__ ("a0") = arg1;
        register ulong_t a7 __asm__ ("a7") = call_id;
 
        __asm__ volatile ("ecall"
                          : "+r" (a0)
                          : "r" (a7)
                          : "memory");
        return a0;
}
 
static inline uintptr_t arch_syscall_invoke0(uintptr_t call_id)
{
        register ulong_t a0 __asm__ ("a0");
        register ulong_t a7 __asm__ ("a7") = call_id;
 
        __asm__ volatile ("ecall"
                          : "=r" (a0)
                          : "r" (a7)
                          : "memory");
        return a0;
}
 
#ifdef CONFIG_USERSPACE
static inline bool arch_is_user_context(void)
{
#ifdef CONFIG_SMP
        /*
         * This is painful. There is no way for u-mode code to know if we're
         * currently executing in u-mode without generating a fault, besides
         * stealing a general purpose register away from the standard ABI
         * that is. And a global variable doesn't work on SMP as this must be
         * per-CPU and we could be migrated to another CPU just at the right
         * moment to peek at the wrong CPU variable (and u-mode can't disable
         * preemption either).
         *
         * So, given that we'll have to pay the price of an exception entry
         * anyway, let's at least make it free to privileged threads by using
         * the mscratch register as the non-user context indicator (it must
         * be zero in m-mode for exception entry to work properly). In the
         * case of u-mode we'll simulate a proper return value in the
         * exception trap code. Let's settle on the return value in t0
         * and omit the volatile to give the compiler a chance to cache
         * the result.
         */
        register ulong_t is_user __asm__ ("t0");
        __asm__ ("csrr %0, mscratch" : "=r" (is_user));
        return is_user != 0;
#else
        /* Defined in arch/riscv/core/thread.c */
        extern uint32_t is_user_mode;
        return is_user_mode;
#endif
}
#endif
 
#ifdef __cplusplus
}
#endif
 
#endif /* _ASMLANGUAGE */
#endif /* ZEPHYR_INCLUDE_ARCH_RISCV_SYSCALL_H_ */