syscall.h

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/*
 * Copyright (c) 2018 Linaro Limited.
 * Copyright 2025 Arm Limited and/or its affiliates <open-source-office@arm.com>
 *
 * SPDX-License-Identifier: Apache-2.0
 */

 
#ifndef ZEPHYR_INCLUDE_ARCH_ARM_SYSCALL_H_
#define ZEPHYR_INCLUDE_ARCH_ARM_SYSCALL_H_
 
#define _SVC_CALL_CONTEXT_SWITCH        0
#define _SVC_CALL_IRQ_OFFLOAD           1
#define _SVC_CALL_RUNTIME_EXCEPT        2
#define _SVC_CALL_SYSTEM_CALL           3
 
#ifdef CONFIG_USERSPACE
#ifndef _ASMLANGUAGE
 
#include <zephyr/types.h>
#include <stdbool.h>
#include <zephyr/arch/arm/misc.h>
#include <zephyr/sys/util_macro.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
 
/* Syscall invocation macros. arm-specific machine constraints used to ensure
 * args land in the proper registers.
 *
 * Note: r6 carries the syscall call_id into the SVC. The SVC handler
 * (z_arm_do_syscall) clobbers r6 while indexing the syscall dispatch table and
 * the exception return does not restore it. r6 must therefore be declared as a
 * read-write ("+r") operand, otherwise the compiler may assume it survives the
 * SVC and hoist the (loop-invariant) call_id load out of a retry loop, causing
 * subsequent iterations to issue the SVC with a corrupted call_id.
 */
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 uint32_t ret __asm__("r0") = arg1;
        register uint32_t r1 __asm__("r1") = arg2;
        register uint32_t r2 __asm__("r2") = arg3;
        register uint32_t r3 __asm__("r3") = arg4;
        register uint32_t r4 __asm__("r4") = arg5;
        register uint32_t r5 __asm__("r5") = arg6;
        register uint32_t r6 __asm__("r6") = call_id;
 
        __asm__ volatile("svc %[svid]\n"
                         IF_ENABLED(CONFIG_ARM_BTI, ("bti\n"))
                         : "=r"(ret), "=r"(r1), "=r"(r2), "=r"(r3), "+r" (r6)
                         : [svid] "i" (_SVC_CALL_SYSTEM_CALL),
                           "r" (ret), "r" (r1), "r" (r2), "r" (r3),
                           "r" (r4), "r" (r5)
                         : "r8", "memory", "ip");
 
        return ret;
}
 
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 uint32_t ret __asm__("r0") = arg1;
        register uint32_t r1 __asm__("r1") = arg2;
        register uint32_t r2 __asm__("r2") = arg3;
        register uint32_t r3 __asm__("r3") = arg4;
        register uint32_t r4 __asm__("r4") = arg5;
        register uint32_t r6 __asm__("r6") = call_id;
 
        __asm__ volatile("svc %[svid]\n"
                         IF_ENABLED(CONFIG_ARM_BTI, ("bti\n"))
                         : "=r"(ret), "=r"(r1), "=r"(r2), "=r"(r3), "+r" (r6)
                         : [svid] "i" (_SVC_CALL_SYSTEM_CALL),
                           "r" (ret), "r" (r1), "r" (r2), "r" (r3),
                           "r" (r4)
                         : "r8", "memory", "ip");
 
        return ret;
}
 
static inline uintptr_t arch_syscall_invoke4(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t arg3, uintptr_t arg4,
                                             uintptr_t call_id)
{
        register uint32_t ret __asm__("r0") = arg1;
        register uint32_t r1 __asm__("r1") = arg2;
        register uint32_t r2 __asm__("r2") = arg3;
        register uint32_t r3 __asm__("r3") = arg4;
        register uint32_t r6 __asm__("r6") = call_id;
 
        __asm__ volatile("svc %[svid]\n"
                         IF_ENABLED(CONFIG_ARM_BTI, ("bti\n"))
                         : "=r"(ret), "=r"(r1), "=r"(r2), "=r"(r3), "+r" (r6)
                         : [svid] "i" (_SVC_CALL_SYSTEM_CALL),
                           "r" (ret), "r" (r1), "r" (r2), "r" (r3)
                         : "r8", "memory", "ip");
 
        return ret;
}
 
static inline uintptr_t arch_syscall_invoke3(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t arg3,
                                             uintptr_t call_id)
{
        register uint32_t ret __asm__("r0") = arg1;
        register uint32_t r1 __asm__("r1") = arg2;
        register uint32_t r2 __asm__("r2") = arg3;
        register uint32_t r6 __asm__("r6") = call_id;
 
        __asm__ volatile("svc %[svid]\n"
                         IF_ENABLED(CONFIG_ARM_BTI, ("bti\n"))
                         : "=r"(ret), "=r"(r1), "=r"(r2), "+r" (r6)
                         : [svid] "i" (_SVC_CALL_SYSTEM_CALL),
                           "r" (ret), "r" (r1), "r" (r2)
                         : "r8", "memory", "r3", "ip");
 
        return ret;
}
 
static inline uintptr_t arch_syscall_invoke2(uintptr_t arg1, uintptr_t arg2,
                                             uintptr_t call_id)
{
        register uint32_t ret __asm__("r0") = arg1;
        register uint32_t r1 __asm__("r1") = arg2;
        register uint32_t r6 __asm__("r6") = call_id;
 
        __asm__ volatile("svc %[svid]\n"
                         IF_ENABLED(CONFIG_ARM_BTI, ("bti\n"))
                         : "=r"(ret), "=r"(r1), "+r" (r6)
                         : [svid] "i" (_SVC_CALL_SYSTEM_CALL),
                           "r" (ret), "r" (r1)
                         : "r8", "memory", "r2", "r3", "ip");
 
        return ret;
}
 
static inline uintptr_t arch_syscall_invoke1(uintptr_t arg1,
                                             uintptr_t call_id)
{
        register uint32_t ret __asm__("r0") = arg1;
        register uint32_t r6 __asm__("r6") = call_id;
 
        __asm__ volatile("svc %[svid]\n"
                         IF_ENABLED(CONFIG_ARM_BTI, ("bti\n"))
                         : "=r"(ret), "+r" (r6)
                         : [svid] "i" (_SVC_CALL_SYSTEM_CALL),
                           "r" (ret)
                         : "r8", "memory", "r1", "r2", "r3", "ip");
        return ret;
}
 
static inline uintptr_t arch_syscall_invoke0(uintptr_t call_id)
{
        register uint32_t ret __asm__("r0");
        register uint32_t r6 __asm__("r6") = call_id;
 
        __asm__ volatile("svc %[svid]\n"
                         IF_ENABLED(CONFIG_ARM_BTI, ("bti\n"))
                         : "=r"(ret), "+r" (r6)
                         : [svid] "i" (_SVC_CALL_SYSTEM_CALL),
                           "r" (ret)
                         : "r8", "memory", "r1", "r2", "r3", "ip");
 
        return ret;
}
 
static inline bool arch_is_user_context(void)
{
#if defined(CONFIG_CPU_CORTEX_M)
        uint32_t value;
 
        /* check for handler mode */
        __asm__ volatile("mrs %0, IPSR\n\t" : "=r"(value));
        if (value) {
                return false;
        }
#endif
 
        return z_arm_thread_is_in_user_mode();
}
 
#ifdef __cplusplus
}
#endif
 
#endif /* _ASMLANGUAGE */
#endif /* CONFIG_USERSPACE */
#endif /* ZEPHYR_INCLUDE_ARCH_ARM_SYSCALL_H_ */