i386/junos/MIT/src.xv6/syscall.c

   1 #include "types.h"
   2 #include "defs.h"
   3 #include "param.h"
   4 #include "memlayout.h"
   5 #include "mmu.h"
   6 #include "proc.h"
   7 #include "x86.h"
   8 #include "syscall.h"
   9
  10 // User code makes a system call with INT T_SYSCALL.
  11 // System call number in %eax.
  12 // Arguments on the stack, from the user call to the C
  13 // library system call function. The saved user %esp points
  14 // to a saved program counter, and then the first argument.
  15
  16 // Fetch the int at addr from the current process.
  17 int
  18 fetchint(uint addr, int *ip)
  19 {
  20   if(addr >= proc->sz || addr+4 > proc->sz)
  21     return -1;
  22   *ip = *(int*)(addr);
  23   return 0;
  24 }
  25
  26 // Fetch the nul-terminated string at addr from the current process.
  27 // Doesn't actually copy the string - just sets *pp to point at it.
  28 // Returns length of string, not including nul.
  29 int
  30 fetchstr(uint addr, char **pp)
  31 {
  32   char *s, *ep;
  33
  34   if(addr >= proc->sz)
  35     return -1;
  36   *pp = (char*)addr;
  37   ep = (char*)proc->sz;
  38   for(s = *pp; s < ep; s++)
  39     if(*s == 0)
  40       return s - *pp;
  41   return -1;
  42 }
  43
  44 // Fetch the nth 32-bit system call argument.
  45 int
  46 argint(int n, int *ip)
  47 {
  48   return fetchint(proc->tf->esp + 4 + 4*n, ip);
  49 }
  50
  51 // Fetch the nth word-sized system call argument as a pointer
  52 // to a block of memory of size n bytes.  Check that the pointer
  53 // lies within the process address space.
  54 int
  55 argptr(int n, char **pp, int size)
  56 {
  57   int i;
  58
  59   if(argint(n, &i) < 0)
  60     return -1;
  61   if((uint)i >= proc->sz || (uint)i+size > proc->sz)
  62     return -1;
  63   *pp = (char*)i;
  64   return 0;
  65 }
  66
  67 // Fetch the nth word-sized system call argument as a string pointer.
  68 // Check that the pointer is valid and the string is nul-terminated.
  69 // (There is no shared writable memory, so the string can't change
  70 // between this check and being used by the kernel.)
  71 int
  72 argstr(int n, char **pp)
  73 {
  74   int addr;
  75   if(argint(n, &addr) < 0)
  76     return -1;
  77   return fetchstr(addr, pp);
  78 }
  79
  80 extern int sys_chdir(void);
  81 extern int sys_close(void);
  82 extern int sys_dup(void);
  83 extern int sys_exec(void);
  84 extern int sys_exit(void);
  85 extern int sys_fork(void);
  86 extern int sys_fstat(void);
  87 extern int sys_getpid(void);
  88 extern int sys_kill(void);
  89 extern int sys_link(void);
  90 extern int sys_mkdir(void);
  91 extern int sys_mknod(void);
  92 extern int sys_open(void);
  93 extern int sys_pipe(void);
  94 extern int sys_read(void);
  95 extern int sys_sbrk(void);
  96 extern int sys_sleep(void);
  97 extern int sys_unlink(void);
  98 extern int sys_wait(void);
  99 extern int sys_write(void);
 100 extern int sys_uptime(void);
 101
 102 static int (*syscalls[])(void) = {
 103 [SYS_fork]    sys_fork,
 104 [SYS_exit]    sys_exit,
 105 [SYS_wait]    sys_wait,
 106 [SYS_pipe]    sys_pipe,
 107 [SYS_read]    sys_read,
 108 [SYS_kill]    sys_kill,
 109 [SYS_exec]    sys_exec,
 110 [SYS_fstat]   sys_fstat,
 111 [SYS_chdir]   sys_chdir,
 112 [SYS_dup]     sys_dup,
 113 [SYS_getpid]  sys_getpid,
 114 [SYS_sbrk]    sys_sbrk,
 115 [SYS_sleep]   sys_sleep,
 116 [SYS_uptime]  sys_uptime,
 117 [SYS_open]    sys_open,
 118 [SYS_write]   sys_write,
 119 [SYS_mknod]   sys_mknod,
 120 [SYS_unlink]  sys_unlink,
 121 [SYS_link]    sys_link,
 122 [SYS_mkdir]   sys_mkdir,
 123 [SYS_close]   sys_close,
 124 };
 125
 126 void
 127 syscall(void)
 128 {
 129   int num;
 130
 131   num = proc->tf->eax;
 132   if(num >= 0 && num < SYS_open && syscalls[num]) {
 133     proc->tf->eax = syscalls[num]();
 134   } else if (num >= SYS_open && num < NELEM(syscalls) && syscalls[num]) {
 135     proc->tf->eax = syscalls[num]();
 136   } else {
 137     cprintf("%d %s: unknown sys call %d\n",
 138             proc->pid, proc->name, num);
 139     proc->tf->eax = -1;
 140   }
 141 }