Minor - introduce GDT_GRANLIMIT macro.

Add macro to improve readability of GDT limit definitions.

diff --git a/src/misc.c b/src/misc.c
index 108c3326e34ac7002860b9d3d15e0e69898be3cb..5cb4a01602279b0c6d0b0a07fdc05f1ac3ce1b99 100644 (file)
--- a/src/misc.c
+++ b/src/misc.c
@@ -149,17 +149,17 @@ u64 rombios32_gdt[] VAR16VISIBLE __aligned(8) = {
     // First entry can't be used.
     0x0000000000000000LL,
     // 32 bit flat code segment (SEG32_MODE32_CS)
-    GDT_LIMIT(0xfffff) | GDT_CODE | GDT_B | GDT_G,
+    GDT_GRANLIMIT(0xffffffff) | GDT_CODE | GDT_B,
     // 32 bit flat data segment (SEG32_MODE32_DS)
-    GDT_LIMIT(0xfffff) | GDT_DATA | GDT_B | GDT_G,
+    GDT_GRANLIMIT(0xffffffff) | GDT_DATA | GDT_B,
     // 16 bit code segment base=0xf0000 limit=0xffff (SEG32_MODE16_CS)
     GDT_LIMIT(BUILD_BIOS_SIZE-1) | GDT_CODE | GDT_BASE(BUILD_BIOS_ADDR),
     // 16 bit data segment base=0x0 limit=0xffff (SEG32_MODE16_DS)
     GDT_LIMIT(0x0ffff) | GDT_DATA,
     // 16 bit code segment base=0xf0000 limit=0xffffffff (SEG32_MODE16BIG_CS)
-    GDT_LIMIT(0xfffff) | GDT_CODE | GDT_G | GDT_BASE(BUILD_BIOS_ADDR),
+    GDT_GRANLIMIT(0xffffffff) | GDT_CODE | GDT_BASE(BUILD_BIOS_ADDR),
     // 16 bit data segment base=0 limit=0xffffffff (SEG32_MODE16BIG_DS)
-    GDT_LIMIT(0xfffff) | GDT_DATA | GDT_G,
+    GDT_GRANLIMIT(0xffffffff) | GDT_DATA,
 };
 
 // GDT descriptor

diff --git a/src/util.h b/src/util.h
index 85cf3f5411e16a2ee74acbda621893f0c0810865..63999e0ff368e878f9a5bbc99e5743c24f9b401f 100644 (file)
--- a/src/util.h
+++ b/src/util.h
@@ -162,15 +162,19 @@ static inline u8 readb(const void *addr) {
             : "ebx", "edx", "esi", "edi", "cc", "memory");              \
     } while (0)
 
-// GDT bit manipulation
-#define GDT_BASE(v)  ((((u64)(v) & 0xff000000) << 32)           \
-                      | (((u64)(v) & 0x00ffffff) << 16))
-#define GDT_LIMIT(v) ((((u64)(v) & 0x000f0000) << 32)   \
-                      | (((u64)(v) & 0x0000ffff) << 0))
+// GDT bits
 #define GDT_CODE     (0x9bULL << 40) // Code segment - P,R,A bits also set
 #define GDT_DATA     (0x93ULL << 40) // Data segment - W,A bits also set
 #define GDT_B        (0x1ULL << 54)  // Big flag
 #define GDT_G        (0x1ULL << 55)  // Granularity flag
+// GDT bits for segment base
+#define GDT_BASE(v)  ((((u64)(v) & 0xff000000) << 32)           \
+                      | (((u64)(v) & 0x00ffffff) << 16))
+// GDT bits for segment limit (0-1Meg)
+#define GDT_LIMIT(v) ((((u64)(v) & 0x000f0000) << 32)   \
+                      | (((u64)(v) & 0x0000ffff) << 0))
+// GDT bits for segment limit (0-4Gig in 4K chunks)
+#define GDT_GRANLIMIT(v) (GDT_G | GDT_LIMIT((v) >> 12))
 
 struct descloc_s {
     u16 length;