| /* |
| * Copyright (c) 2016 Jean-Paul Etienne <fractalclone@gmail.com> |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| */ |
| |
| #include <irq.h> |
| #include <kernel_structs.h> |
| #include <offsets_short.h> |
| |
| /* exports */ |
| GTEXT(__swap) |
| GTEXT(_thread_entry_wrapper) |
| |
| /* Use ABI name of registers for the sake of simplicity */ |
| |
| /* |
| * unsigned int __swap(unsigned int key) |
| * |
| * Always called with interrupts locked |
| * key is stored in a0 register |
| */ |
| SECTION_FUNC(exception.other, __swap) |
| |
| /* Make a system call to perform context switch */ |
| ecall |
| |
| /* |
| * when thread is rescheduled, unlock irq and return. |
| * Restored register a0 contains IRQ lock state of thread. |
| * |
| * Prior to unlocking irq, load return value of |
| * __swap to temp register t2 (from |
| * _thread_offset_to_swap_return_value). Normally, it should be -EAGAIN, |
| * unless someone has previously called _set_thread_return_value(..). |
| */ |
| la t0, _kernel |
| |
| /* Get pointer to _kernel.current */ |
| lw t1, _kernel_offset_to_current(t0) |
| |
| /* Load return value of __swap function in temp register t2 */ |
| lw t2, _thread_offset_to_swap_return_value(t1) |
| |
| /* |
| * Unlock irq, following IRQ lock state in a0 register. |
| * Use atomic instruction csrrs to do so. |
| */ |
| andi a0, a0, SOC_MSTATUS_IEN |
| csrrs t0, mstatus, a0 |
| |
| /* Set value of return register a0 to value of register t2 */ |
| addi a0, t2, 0 |
| |
| /* Return */ |
| jalr x0, ra |
| |
| |
| /* |
| * void _thread_entry_wrapper(k_thread_entry_t, void *, void *, void *) |
| */ |
| SECTION_FUNC(TEXT, _thread_entry_wrapper) |
| /* |
| * _thread_entry_wrapper is called for every new thread upon the return |
| * of __swap or ISR. Its address, as well as its input function |
| * arguments thread_entry_t, void *, void *, void * are restored from |
| * the thread stack (initialized via function _thread). |
| * In this case, thread_entry_t, * void *, void * and void * are stored |
| * in registers a0, a1, a2 and a3. These registers are used as arguments |
| * to function _thread_entry. Hence, just call _thread_entry with |
| * return address set to 0 to indicate a non-returning function call. |
| */ |
| |
| jal x0, _thread_entry |
