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53 lines
1.5 KiB
53 lines
1.5 KiB
/*
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* Supervisor-mode startup codes
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*/
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#include "riscv.h"
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#include "string.h"
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#include "elf.h"
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#include "process.h"
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#include "spike_interface/spike_utils.h"
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// process is a structure defined in kernel/process.h
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process user_app;
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//
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// load the elf, and construct a "process" (with only a trapframe).
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// load_bincode_from_host_elf is defined in elf.c
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//
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void load_user_program(process *proc) {
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// USER_TRAP_FRAME is a physical address defined in kernel/config.h
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proc->trapframe = (trapframe *)USER_TRAP_FRAME;
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memset(proc->trapframe, 0, sizeof(trapframe));
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// USER_KSTACK is also a physical address defined in kernel/config.h
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proc->kstack = USER_KSTACK;
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proc->trapframe->regs.sp = USER_STACK;
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// load_bincode_from_host_elf() is defined in kernel/elf.c
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load_bincode_from_host_elf(proc);
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}
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//
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// s_start: S-mode entry point of riscv-pke OS kernel.
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//
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int s_start(void) {
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sprint("Enter supervisor mode...\n");
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// Note: we use direct (i.e., Bare mode) for memory mapping in lab1.
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// which means: Virtual Address = Physical Address
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// therefore, we need to set satp to be 0 for now. we will enable paging in lab2_x.
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//
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// write_csr is a macro defined in kernel/riscv.h
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write_csr(satp, 0);
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// the application code (elf) is first loaded into memory, and then put into execution
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load_user_program(&user_app);
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sprint("Switch to user mode...\n");
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// switch_to() is defined in kernel/process.c
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switch_to(&user_app);
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// we should never reach here.
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return 0;
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}
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