making win+space work when no tasks are running

1 files changed, 6 insertions, 4 deletions

diff --git a/src/kernel/paging.c b/src/kernel/paging.c
index 4672788..0432ab6 100644
--- a/src/kernel/paging.c
+++ b/src/kernel/paging.c
@@ -132,7 +132,8 @@ void init_paging() {
 
 __attribute__ ((pure))
 void *vma_to_pma(void *pd, const void *vma) {
-  return (void *)(((uint32_t *)(((uint32_t *)pd)[(uint32_t)vma >> 22] & PE_ADDR_MASK))[((uint32_t)vma >> 12) % 1024] & PE_ADDR_MASK) + (uint32_t)vma % 4096;
+  //this is maybe not good - in the case where pd is zero, vma is returned unconsted. hopefully this doesn't become a problem.
+  return pd ? (void *)(((uint32_t *)(((uint32_t *)pd)[(uint32_t)vma >> 22] & PE_ADDR_MASK))[((uint32_t)vma >> 12) % 1024] & PE_ADDR_MASK) + (uint32_t)vma % 4096 : (void *)(uint32_t)vma;
 }
 
 void switch_to_kernel_cr3() {
@@ -143,7 +144,8 @@ void switch_to_kernel_cr3() {
 }
 
 void switch_to_task_cr3() {
-  asm volatile (
-    "mov %0, %%cr3"
-  : : "a" (active_task->page_directory));
+  if (active_task->page_directory)
+    asm volatile (
+      "mov %0, %%cr3"
+    : : "a" (active_task->page_directory));
 }
\ No newline at end of file