96 lines
2.5 KiB
C
96 lines
2.5 KiB
C
#include "types.h"
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#include "defs.h"
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#include "param.h"
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#include "memlayout.h"
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#include "mmu.h"
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#include "proc.h"
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#include "x86.h"
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#include "syscall.h"
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#include "syscalltable.h"
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// User code makes a system call with INT T_SYSCALL.
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// System call number in %eax.
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// Arguments on the stack, from the user call to the C
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// library system call function. The saved user %esp points
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// to a saved program counter, and then the first argument.
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// Fetch the int at addr from the current process.
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int fetchint(uint addr, int *ip) {
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struct proc *curproc = myproc();
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if (addr >= curproc->sz || addr + 4 > curproc->sz) {
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return -1;
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}
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*ip = *(int*)(addr);
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return 0;
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}
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// Fetch the nul-terminated string at addr from the current process.
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// Doesn't actually copy the string - just sets *pp to point at it.
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// Returns length of string, not including nul.
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int fetchstr(uint addr, char **pp) {
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char *s, *ep;
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struct proc *curproc = myproc();
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if (addr >= curproc->sz) {
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return -1;
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}
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*pp = (char*)addr;
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ep = (char*)curproc->sz;
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for (s = *pp; s < ep; s++) {
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if (*s == 0) {
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return s - *pp;
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}
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}
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return -1;
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}
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// Fetch the nth 32-bit system call argument.
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int argint(int n, int *ip) {
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return fetchint((myproc()->tf->esp) + 4 + 4 * n, ip);
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}
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// Fetch the nth word-sized system call argument as a pointer
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// to a block of memory of size bytes. Check that the pointer
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// lies within the process address space.
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int argptr(int n, char **pp, int size) {
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int i;
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struct proc *curproc = myproc();
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if (argint(n, &i) < 0) {
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return -1;
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}
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if (size < 0 || (uint)i >= curproc->sz || (uint)i + size > curproc->sz) {
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return -1;
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}
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*pp = (char*)i;
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return 0;
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}
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// Fetch the nth word-sized system call argument as a string pointer.
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// Check that the pointer is valid and the string is nul-terminated.
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// (There is no shared writable memory, so the string can't change
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// between this check and being used by the kernel.)
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int argstr(int n, char **pp) {
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int addr;
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if (argint(n, &addr) < 0) {
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return -1;
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}
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return fetchstr(addr, pp);
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}
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void syscall(void) {
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int num;
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struct proc *curproc = myproc();
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num = curproc->tf->eax;
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if (num > 0 && num < NELEM(syscalls) && syscalls[num]) {
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curproc->tf->eax = syscalls[num]();
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}
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else {
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cprintf("%d %s: unknown sys call %d\n",
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curproc->pid, curproc->name, num);
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curproc->tf->eax = -1;
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}
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}
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