kern/syscall.c

   1 /* See COPYRIGHT for copyright information. */
   2
   3 #include <inc/x86.h>
   4 #include <inc/error.h>
   5 #include <inc/string.h>
   6 #include <inc/assert.h>
   7
   8 #include <kern/env.h>
   9 #include <kern/pmap.h>
  10 #include <kern/trap.h>
  11 #include <kern/syscall.h>
  12 #include <kern/console.h>
  13
  14 // Print a string to the system console.
  15 // The string is exactly 'len' characters long.
  16 // Destroys the environment on memory errors.
  17 static void
  18 sys_cputs(const char *s, size_t len)
  19 {
  20         // Check that the user has permission to read memory [s, s+len).
  21         // Destroy the environment if not.
  22         // LAB 3: Your code here.
  23         user_mem_assert(curenv, (void *)s, len, 0);
  24
  25         // Print the string supplied by the user.
  26         cprintf("%.*s", len, s);
  27 }
  28
  29 // Read a character from the system console.
  30 // Returns the character.
  31 static int
  32 sys_cgetc(void)
  33 {
  34         int c;
  35
  36         // The cons_getc() primitive doesn't wait for a character,
  37         // but the sys_cgetc() system call does.
  38         while ((c = cons_getc()) == 0)
  39                 /* do nothing */;
  40
  41         return c;
  42 }
  43
  44 // Returns the current environment's envid.
  45 static envid_t
  46 sys_getenvid(void)
  47 {
  48         return curenv->env_id;
  49 }
  50
  51 // Destroy a given environment (possibly the currently running environment).
  52 //
  53 // Returns 0 on success, < 0 on error.  Errors are:
  54 //      -E_BAD_ENV if environment envid doesn't currently exist,
  55 //              or the caller doesn't have permission to change envid.
  56 static int
  57 sys_env_destroy(envid_t envid)
  58 {
  59         int r;
  60         struct Env *e;
  61
  62         if ((r = envid2env(envid, &e, 1)) < 0)
  63                 return r;
  64         if (e == curenv)
  65                 cprintf("[%08x] exiting gracefully\n", curenv->env_id);
  66         else
  67                 cprintf("[%08x] destroying %08x\n", curenv->env_id, e->env_id);
  68         env_destroy(e);
  69         return 0;
  70 }
  71
  72 // Dispatches to the correct kernel function, passing the arguments.
  73 int32_t
  74 syscall(uint32_t syscallno, uint32_t a1, uint32_t a2, uint32_t a3, uint32_t a4, uint32_t a5)
  75 {
  76         // Call the function corresponding to the 'syscallno' parameter.
  77         // Return any appropriate return value.
  78         // LAB 3: Your code here.
  79         int ret = 0;
  80
  81         switch (syscallno) {
  82         case SYS_cputs:
  83                 sys_cputs((const char *)a1, (size_t)a2);
  84                 break;
  85         case SYS_cgetc:
  86                 ret = sys_cgetc();
  87                 break;
  88         case SYS_getenvid:
  89                 ret = sys_getenvid();
  90                 break;
  91         case SYS_env_destroy:
  92                 ret = sys_env_destroy((envid_t)a1);
  93                 break;
  94         default:
  95                 // NSYSCALLS
  96                 ret = -E_INVAL;
  97                 break;
  98         }
  99
 100         return ret;
 101 }
 102