150 lines
3.6 KiB
C
150 lines
3.6 KiB
C
#include "types.h"
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#include "param.h"
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#include "memlayout.h"
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#include "riscv.h"
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#include "proc.h"
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#include "defs.h"
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#include "elf.h"
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static int loadseg(pde_t *pgdir, uint64 addr, struct inode *ip, uint offset, uint sz);
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int
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exec(char *path, char **argv)
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{
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char *s, *last;
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int i, off;
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uint64 argc, sz, sp, ustack[MAXARG+1], stackbase;
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struct elfhdr elf;
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struct inode *ip;
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struct proghdr ph;
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pagetable_t pagetable = 0, oldpagetable;
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struct proc *p = myproc();
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uint64 oldsz = p->sz;
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begin_op();
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if((ip = namei(path)) == 0){
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end_op();
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return -1;
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}
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ilock(ip);
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// Check ELF header
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if(readi(ip, 0, (uint64)&elf, 0, sizeof(elf)) != sizeof(elf))
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goto bad;
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if(elf.magic != ELF_MAGIC)
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goto bad;
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if((pagetable = proc_pagetable(p)) == 0)
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goto bad;
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// Load program into memory.
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sz = 0;
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for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
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if(readi(ip, 0, (uint64)&ph, off, sizeof(ph)) != sizeof(ph))
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goto bad;
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if(ph.type != ELF_PROG_LOAD)
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continue;
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if(ph.memsz < ph.filesz)
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goto bad;
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if(ph.vaddr + ph.memsz < ph.vaddr)
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goto bad;
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if((sz = uvmalloc(pagetable, sz, ph.vaddr + ph.memsz)) == 0)
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goto bad;
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if(ph.vaddr % PGSIZE != 0)
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goto bad;
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if(loadseg(pagetable, ph.vaddr, ip, ph.off, ph.filesz) < 0)
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goto bad;
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}
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iunlockput(ip);
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end_op();
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ip = 0;
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// Allocate two pages at the next page boundary.
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// Use the second as the user stack.
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sz = PGROUNDUP(sz);
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if((sz = uvmalloc(pagetable, sz, sz + 2*PGSIZE)) == 0)
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goto bad;
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sp = sz;
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stackbase = sp - PGSIZE;
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// Push argument strings, prepare rest of stack in ustack.
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for(argc = 0; argv[argc]; argc++) {
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if(argc >= MAXARG)
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goto bad;
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sp -= strlen(argv[argc]) + 1;
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sp -= sp % 16; // riscv sp must be 16-byte aligned
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if(sp < stackbase)
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goto bad;
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if(copyout(pagetable, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
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goto bad;
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ustack[argc] = sp;
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}
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ustack[argc] = 0;
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// push the array of argv[] pointers.
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sp -= (argc+1) * sizeof(uint64);
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sp -= sp % 16;
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if(sp < stackbase)
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goto bad;
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if(copyout(pagetable, sp, (char *)ustack, (argc+1)*sizeof(uint64)) < 0)
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goto bad;
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// arguments to user main(argc, argv)
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// argc is returned via the system call return
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// value, which goes in a0.
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p->tf->a1 = sp;
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// Save program name for debugging.
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for(last=s=path; *s; s++)
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if(*s == '/')
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last = s+1;
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safestrcpy(p->name, last, sizeof(p->name));
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// Commit to the user image.
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oldpagetable = p->pagetable;
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p->pagetable = pagetable;
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p->sz = sz;
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p->tf->epc = elf.entry; // initial program counter = main
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p->tf->sp = sp; // initial stack pointer
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proc_freepagetable(oldpagetable, oldsz);
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return argc; // this ends up in a0, the first argument to main(argc, argv)
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bad:
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if(pagetable)
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proc_freepagetable(pagetable, sz);
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if(ip){
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iunlockput(ip);
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end_op();
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}
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return -1;
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}
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// Load a program segment into pagetable at virtual address va.
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// va must be page-aligned
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// and the pages from va to va+sz must already be mapped.
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// Returns 0 on success, -1 on failure.
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static int
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loadseg(pagetable_t pagetable, uint64 va, struct inode *ip, uint offset, uint sz)
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{
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uint i, n;
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uint64 pa;
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if((va % PGSIZE) != 0)
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panic("loadseg: va must be page aligned");
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for(i = 0; i < sz; i += PGSIZE){
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pa = walkaddr(pagetable, va + i);
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if(pa == 0)
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panic("loadseg: address should exist");
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if(sz - i < PGSIZE)
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n = sz - i;
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else
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n = PGSIZE;
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if(readi(ip, 0, (uint64)pa, offset+i, n) != n)
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return -1;
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}
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return 0;
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}
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