gdt: expose code segment offset in GDT

gdt_get_code_offset() returns the offset of the code segment in the GDT
relative to the address of the GDT itself.  This offset is for example
required when setting the interrupt desriptor table.

2 files changed, 6 insertions, 0 deletions

diff --git a/core/gdt.c b/core/gdt.c
index 708e2c5..b59bf9e 100644
--- a/core/gdt.c
+++ b/core/gdt.c
@@ -74,3 +74,8 @@ void gdt_init(void)
 
 	gdtset(gdtp);
 }
+
+uint16_t gdt_get_code_offset(void)
+{
+	return GDT_SGMT_CODE * sizeof(*gdt);
+}
diff --git a/include/garmos/gdt.h b/include/garmos/gdt.h
index b49f42d..d353437 100644
--- a/include/garmos/gdt.h
+++ b/include/garmos/gdt.h
@@ -18,5 +18,6 @@
 #include <garmos/types.h>
 
 void gdt_init(void);
+uint16_t gdt_get_code_offset(void);
 
 #endif