bug fixes

- needed an atomic_load() when getting the count in
  pic8253_nanoseconds_elapsed()

- i was deleting half the bits of the outgoing task's stack in
  cpu_task.S (oops)

- updated .gdbint. TODO: automate laoding section offsets correctly

3 files changed, 9 insertions, 4 deletions

diff --git a/.gdbinit b/.gdbinit
index 9faf2b9..7fc534d 100644
--- a/.gdbinit
+++ b/.gdbinit
@@ -1,3 +1,3 @@
 target remote localhost:1234
-add-symbol-file kc/core/kernel.os 0xffffffff80001000 -s .data 0xffffffff80005000
+add-symbol-file kc/core/kernel.os 0xffffffff80001000 -s .data 0xffffffff80006000
 
diff --git a/kc/core/cpu/cpu_task.S b/kc/core/cpu/cpu_task.S
index f2fb473..4f9fd7b 100644
--- a/kc/core/cpu/cpu_task.S
+++ b/kc/core/cpu/cpu_task.S
@@ -17,6 +17,10 @@ cpu_set_thread:
     *   rsi: pointer to control block of the current thread
     *   rdx: pointer to this cpu's task state segment esp0 field
     */
+    // test for a NULL origin thread
+    test %rsi,%rsi
+    // skip saving the state for a NULL origin thread
+    jz .Lnull_thread
     push %rbx
     push %r12
     push %r13
@@ -24,7 +28,8 @@ cpu_set_thread:
     push %r15
     push %rbp
     /* the current task will be in rsi */
-    mov %esp, 0(%rsi) // save the stack pointer for the current task
+    mov %rsp, 0(%rsi) // save the stack pointer for the current task
+.Lnull_thread:
     mov 0(%rdi),%rsp // new stack is the next's task's stack
     mov 8(%rdi),%rbx // top of the next task's kernel stack
     mov %rbx,0(%rdx) // save the esp0 to the tss
diff --git a/kc/core/pit8253.c b/kc/core/pit8253.c
index 4728020..6f6256a 100644
--- a/kc/core/pit8253.c
+++ b/kc/core/pit8253.c
@@ -21,7 +21,7 @@
 
 static void pit8253_set_divisor(uint16_t divisor);
 
-static atomic_uint_fast64_t count = 0;
+static volatile atomic_uint_fast64_t count = 0;
 static uint16_t divisor = 0;
 
 const struct timer_source pit8253_timer_source =
@@ -82,7 +82,7 @@ uint32_t pit8253_get_frequency(void)
 
 uint64_t pit8253_nanoseconds_elapsed(void)
 {
-    return pit8253_nanoseconds_delta() * count;
+    return pit8253_nanoseconds_delta() * atomic_load(&count);
 }
 
 uint64_t pit8253_nanoseconds_delta(void)