i386/MIT/course/src/git.lab/lib/pgfault.c

   1 // User-level page fault handler support.
   2 // Rather than register the C page fault handler directly with the
   3 // kernel as the page fault handler, we register the assembly language
   4 // wrapper in pfentry.S, which in turns calls the registered C
   5 // function.
   6
   7 #include <inc/lib.h>
   8
   9
  10 // Assembly language pgfault entrypoint defined in lib/pfentry.S.
  11 extern void _pgfault_upcall(void);
  12
  13 // Pointer to currently installed C-language pgfault handler.
  14 void (*_pgfault_handler)(struct UTrapframe *utf);
  15
  16 //
  17 // Set the page fault handler function.
  18 // If there isn't one yet, _pgfault_handler will be 0.
  19 // The first time we register a handler, we need to
  20 // allocate an exception stack (one page of memory with its top
  21 // at UXSTACKTOP), and tell the kernel to call the assembly-language
  22 // _pgfault_upcall routine when a page fault occurs.
  23 //
  24 void
  25 set_pgfault_handler(void (*handler)(struct UTrapframe *utf))
  26 {
  27         int r;
  28
  29         if (_pgfault_handler == 0) {
  30                 // First time through!
  31                 // LAB 4: Your code here.
  32                 panic("set_pgfault_handler not implemented");
  33         }
  34
  35         // Save handler pointer for assembly to call.
  36         _pgfault_handler = handler;
  37 }