1 files changed, 131 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
new file mode 100644
index 0000000..f0b79fc
--- /dev/null
+++ b/kernel/sched.c
@@ -0,0 +1,131 @@
+#include <asm/system.h>
+#include <kernel/con.h>
+#include <kernel/memory.h>
+#include <kernel/sched.h>
+#include <string.h>
+#include <sys/types.h>
+
+#define USRSTART ((void*) 0x40000000)
+
+#define pages(n) \
+  ((n / 4096) + 1)
+
+#define tables(n) \
+  ((n / 1024) + 1)
+
+#define getpage(name, p) ({\
+  void **_next; \
+  _next = map_page(p); \
+  name = p; \
+  p = *_next; \
+  })
+
+extern char _usrbin_start;
+extern char _usrbin_size;
+
+struct task_struct *ctask;
+
+static struct task_struct task;
+
+static inline void empty_table(void *t) {
+  int i;
+
+  for(i = 0; i < PGENT; i++)
+    ((uint32_t*) t)[i] = 0;
+}
+
+void userspace_init(void) {
+  int i, j;
+  int c;
+  size_t totpages, npages, ntables;
+  void *p, *page, *tab, *map;
+  void *pdir, *stackt, *stackp;
+
+  size_t usrsize = (size_t) &_usrbin_size;
+
+  npages = pages(usrsize);
+  ntables = tables(pages(usrsize));
+  totpages = npages + ntables + 3;
+
+  /* here we allocate pages to setup the process'
+   * address space. in addition to the pages that
+   * will hold the binary image, the following
+   * pages are allocated:
+   *  - page directory (1 page)
+   *  - page tables
+   *  - stack page (1 page)
+   *  - stack table (1 page)
+   */
+  p = alloc_physical_pages(totpages);
+  printf("Allocating %x pages for userspace process\n", totpages);
+  if(p == NULL) {
+    printf("Failed to allocate memory for userspace!\n");
+    return;
+  }
+
+  getpage(pdir, p);
+  getpage(stackt, p);
+  getpage(stackp, p);
+  printf("  Page directory:    0x%08x\n", (uint32_t) pdir);
+  printf("  Stack table:       0x%08x\n", (uint32_t) stackt);
+  printf("  Stack page:        0x%08x\n", (uint32_t) stackp);
+  printf("  Page tables:\n");
+
+  /* populate the page directory */
+  c = npages;
+  map = map_page(pdir);
+  empty_table(map);
+  for(i = 0; i < ntables; i++) {
+    /* add the table entry to the directory */
+    getpage(tab, p);
+    printf("    0x%08x\n", (uint32_t) tab);
+    map = map_page(pdir);
+    ((uint32_t*) map)[i + (PGENT / 4)] = (uint32_t) tab | 0x007;
+
+    /* populate the page table */
+    map = map_page(tab);
+    for(j = 0; j < PGENT; j++) {
+      ((uint32_t*) map)[j] = 0;
+      if(c <= 0)
+        continue;
+
+      getpage(page, p);
+      map = map_page(tab);
+      ((uint32_t*) map)[j] = (uint32_t) page | 0x007;
+      c--;
+    }
+  }
+
+  /* populate the stack table */
+  map = map_page(stackt);
+  empty_table(map);
+  ((uint32_t*) map)[PGENT - 1] = (uint32_t) stackp | 0x007;
+
+  /* add the stack page table to the directory */
+  map = map_page(pdir);
+  ((uint32_t*) map)[PGENT - 1] = (uint32_t) stackt | 0x007;
+  /* add the kernel's page table to the directory */
+  ((uint32_t*) map)[0] = (uint32_t) ktab | 0x003;
+
+  __asm__ volatile ("mov %%eax, %%cr3" :: "a" (pdir));
+
+  memcpy(USRSTART, &_usrbin_start, usrsize);
+
+  /*
+   * here we initialize the task struct.
+   * currently, we only setup state information
+   * necessary to begin execution.
+   */
+  memset(&task, 0, sizeof(task));
+  task.state.cs = 0x1B;
+  task.state.ss = 0x23;
+  task.state.eip = (uint32_t) USRSTART;
+  task.state.esp = 0xFFFFFFFF;
+  __asm__ (
+      "pushf\n" \
+      "pop %%eax" \
+      : "=a" (task.state.eflags) \
+      ::);
+
+  switch_to(&task, &task.state);
+}