65 lines
2.3 KiB
C
65 lines
2.3 KiB
C
/*
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* Copyright (c) 2016 Jean-Paul Etienne <fractalclone@gmail.com>
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <kernel.h>
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#include <ksched.h>
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void z_thread_entry_wrapper(k_thread_entry_t thread,
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void *arg1,
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void *arg2,
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void *arg3);
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void arch_new_thread(struct k_thread *thread, k_thread_stack_t *stack,
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size_t stack_size, k_thread_entry_t thread_func,
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void *arg1, void *arg2, void *arg3,
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int priority, unsigned int options)
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{
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char *stack_memory = Z_THREAD_STACK_BUFFER(stack);
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Z_ASSERT_VALID_PRIO(priority, thread_func);
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struct __esf *stack_init;
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z_new_thread_init(thread, stack_memory, stack_size, priority, options);
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/* Initial stack frame for thread */
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stack_init = (struct __esf *)
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STACK_ROUND_DOWN(stack_memory +
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stack_size - sizeof(struct __esf));
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/* Setup the initial stack frame */
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stack_init->a0 = (ulong_t)thread_func;
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stack_init->a1 = (ulong_t)arg1;
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stack_init->a2 = (ulong_t)arg2;
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stack_init->a3 = (ulong_t)arg3;
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/*
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* Following the RISC-V architecture,
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* the MSTATUS register (used to globally enable/disable interrupt),
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* as well as the MEPC register (used to by the core to save the
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* value of the program counter at which an interrupt/exception occcurs)
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* need to be saved on the stack, upon an interrupt/exception
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* and restored prior to returning from the interrupt/exception.
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* This shall allow to handle nested interrupts.
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*
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* Given that context switching is performed via a system call exception
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* within the RISCV architecture implementation, initially set:
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* 1) MSTATUS to SOC_MSTATUS_DEF_RESTORE in the thread stack to enable
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* interrupts when the newly created thread will be scheduled;
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* 2) MEPC to the address of the z_thread_entry_wrapper in the thread
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* stack.
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* Hence, when going out of an interrupt/exception/context-switch,
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* after scheduling the newly created thread:
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* 1) interrupts will be enabled, as the MSTATUS register will be
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* restored following the MSTATUS value set within the thread stack;
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* 2) the core will jump to z_thread_entry_wrapper, as the program
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* counter will be restored following the MEPC value set within the
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* thread stack.
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*/
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stack_init->mstatus = SOC_MSTATUS_DEF_RESTORE;
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stack_init->mepc = (ulong_t)z_thread_entry_wrapper;
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thread->callee_saved.sp = (ulong_t)stack_init;
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}
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