75 lines
2.0 KiB
ArmAsm
75 lines
2.0 KiB
ArmAsm
/*
|
|
* 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(_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
|