syscalls/modify_ldt.c

   1 #include "arch.h"
   2
   3 #ifdef X86
   4 /*
   5  * asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
   6  */
   7 #include <stdlib.h>
   8 #include <sys/types.h>
   9 #define __ASSEMBLY__ 1
  10 #include <asm/ldt.h>
  11 #include "sanitise.h"
  12 #include "shm.h"
  13
  14 #define ALLOCSIZE LDT_ENTRIES * LDT_ENTRY_SIZE
  15
  16 static void sanitise_modify_ldt(int childno)
  17 {
  18         void *ldt;
  19         //struct user_desc *desc;
  20
  21         shm->scratch[childno] = 0;
  22         switch (shm->syscall[childno].a1) {
  23         case 0:
  24                 /* read the ldt into the memory pointed to by ptr.
  25                    The number of bytes read is the smaller of bytecount and the actual size of the ldt. */
  26                 ldt = malloc(ALLOCSIZE);
  27                 shm->scratch[childno] = (unsigned long) ldt;
  28                 if (ldt == NULL)
  29                         return;
  30                 shm->syscall[childno].a3 = ALLOCSIZE;
  31                 break;
  32
  33         case 1:
  34                 /* modify one ldt entry.
  35                  * ptr points to a user_desc structure
  36                  * bytecount must equal the size of this structure. */
  37
  38         /*
  39                unsigned int  entry_number;
  40                unsigned long base_addr;
  41                unsigned int  limit;
  42                unsigned int  seg_32bit:1;
  43                unsigned int  contents:2;
  44                unsigned int  read_exec_only:1;
  45                unsigned int  limit_in_pages:1;
  46                unsigned int  seg_not_present:1;
  47                unsigned int  useable:1;
  48         */
  49                 break;
  50         default:
  51                 break;
  52         }
  53 }
  54
  55 static void post_modify_ldt(int childno)
  56 {
  57         void *ptr;
  58
  59         ptr = (void *) shm->scratch[childno];
  60
  61         if (ptr != NULL)
  62                 free(ptr);
  63
  64         shm->scratch[childno] = 0;
  65 }
  66
  67 struct syscallentry syscall_modify_ldt = {
  68         .name = "modify_ldt",
  69         .num_args = 3,
  70         .arg1name = "func",
  71         .arg1type = ARG_OP,
  72         .arg1list = {
  73                 .num = 2,
  74                 .values = { 0, 1 },
  75         },
  76         .arg2name = "ptr",
  77         .arg3name = "bytecount",
  78         .sanitise = sanitise_modify_ldt,
  79         .post = post_modify_ldt,
  80 };
  81 #endif