You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
107 lines
3.6 KiB
107 lines
3.6 KiB
/*
|
|
* Supervisor-mode startup codes
|
|
*/
|
|
|
|
#include "riscv.h"
|
|
#include "string.h"
|
|
#include "elf.h"
|
|
#include "process.h"
|
|
#include "pmm.h"
|
|
#include "vmm.h"
|
|
#include "memlayout.h"
|
|
#include "spike_interface/spike_utils.h"
|
|
|
|
// process is a structure defined in kernel/process.h
|
|
process user_app;
|
|
|
|
//
|
|
// trap_sec_start points to the beginning of S-mode trap segment (i.e., the entry point of
|
|
// S-mode trap vector). added @lab2_1
|
|
//
|
|
extern char trap_sec_start[];
|
|
|
|
//
|
|
// turn on paging. added @lab2_1
|
|
//
|
|
void enable_paging() {
|
|
// write the pointer to kernel page (table) directory into the CSR of "satp".
|
|
write_csr(satp, MAKE_SATP(g_kernel_pagetable));
|
|
|
|
// refresh tlb to invalidate its content.
|
|
flush_tlb();
|
|
}
|
|
|
|
//
|
|
// load the elf, and construct a "process" (with only a trapframe).
|
|
// load_bincode_from_host_elf is defined in elf.c
|
|
//
|
|
void load_user_program(process *proc) {
|
|
sprint("User application is loading.\n");
|
|
// allocate a page to store the trapframe. alloc_page is defined in kernel/pmm.c. added @lab2_1
|
|
proc->trapframe = (trapframe *)alloc_page();
|
|
memset(proc->trapframe, 0, sizeof(trapframe));
|
|
|
|
// allocate a page to store page directory. added @lab2_1
|
|
proc->pagetable = (pagetable_t)alloc_page();
|
|
memset((void *)proc->pagetable, 0, PGSIZE);
|
|
|
|
// allocate pages to both user-kernel stack and user app itself. added @lab2_1
|
|
proc->kstack = (uint64)alloc_page() + PGSIZE; //user kernel stack top
|
|
uint64 user_stack = (uint64)alloc_page(); //phisical address of user stack bottom
|
|
|
|
// USER_STACK_TOP = 0x7ffff000, defined in kernel/memlayout.h
|
|
proc->trapframe->regs.sp = USER_STACK_TOP; //virtual address of user stack top
|
|
|
|
sprint("user frame 0x%lx, user stack 0x%lx, user kstack 0x%lx \n", proc->trapframe,
|
|
proc->trapframe->regs.sp, proc->kstack);
|
|
|
|
// load_bincode_from_host_elf() is defined in kernel/elf.c
|
|
load_bincode_from_host_elf(proc);
|
|
|
|
// populate the page table of user application. added @lab2_1
|
|
// map user stack in userspace, user_vm_map is defined in kernel/vmm.c
|
|
user_vm_map((pagetable_t)proc->pagetable, USER_STACK_TOP - PGSIZE, PGSIZE, user_stack,
|
|
prot_to_type(PROT_WRITE | PROT_READ, 1));
|
|
|
|
// map trapframe in user space (direct mapping as in kernel space).
|
|
user_vm_map((pagetable_t)proc->pagetable, (uint64)proc->trapframe, PGSIZE, (uint64)proc->trapframe,
|
|
prot_to_type(PROT_WRITE | PROT_READ, 0));
|
|
|
|
// map S-mode trap vector section in user space (direct mapping as in kernel space)
|
|
// here, we assume that the size of usertrap.S is smaller than a page.
|
|
user_vm_map((pagetable_t)proc->pagetable, (uint64)trap_sec_start, PGSIZE, (uint64)trap_sec_start,
|
|
prot_to_type(PROT_READ | PROT_EXEC, 0));
|
|
}
|
|
|
|
//
|
|
// s_start: S-mode entry point of riscv-pke OS kernel.
|
|
//
|
|
int s_start(void) {
|
|
sprint("Enter supervisor mode...\n");
|
|
// in the beginning, we use Bare mode (direct) memory mapping as in lab1.
|
|
// but now, we are going to switch to the paging mode @lab2_1.
|
|
// note, the code still works in Bare mode when calling pmm_init() and kern_vm_init().
|
|
write_csr(satp, 0);
|
|
|
|
// init phisical memory manager
|
|
pmm_init();
|
|
|
|
// build the kernel page table
|
|
kern_vm_init();
|
|
|
|
// now, switch to paging mode by turning on paging (SV39)
|
|
enable_paging();
|
|
// the code now formally works in paging mode, meaning the page table is now in use.
|
|
sprint("kernel page table is on \n");
|
|
|
|
// the application code (elf) is first loaded into memory, and then put into execution
|
|
load_user_program(&user_app);
|
|
|
|
sprint("Switch to user mode...\n");
|
|
// switch_to() is defined in kernel/process.c
|
|
switch_to(&user_app);
|
|
|
|
// we should never reach here.
|
|
return 0;
|
|
}
|