tiny clarifications to some gdt code.

1 files changed, 4 insertions, 0 deletions

diff --git a/mmu.h b/mmu.h
index 685f51d..310d5de 100644
--- a/mmu.h
+++ b/mmu.h
@@ -39,6 +39,7 @@
 
 #define CR4_PSE         0x00000010      // Page size extension
 
+// various segment selectors.
 #define SEG_KCODE 1  // kernel code
 #define SEG_KDATA 2  // kernel data+stack
 #define SEG_KCPU  3  // kernel per-cpu data
@@ -46,6 +47,9 @@
 #define SEG_UDATA 5  // user data+stack
 #define SEG_TSS   6  // this process's task state
 
+// cpu->gdt[NSEGS] holds the above segments.
+#define NSEGS     7
+
 //PAGEBREAK!
 #ifndef __ASSEMBLER__
 // Segment Descriptor