[src/trunk]: src/sys/arch/amd64/include Give the structure sizes.

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3e937b576eb2
branches:  trunk
changeset: 347548:3e937b576eb2
user:      maxv <maxv%NetBSD.org@localhost>
date:      Fri Sep 02 08:52:12 2016 +0000

description:
Give the structure sizes.

diffstat:

 sys/arch/amd64/include/segments.h |  16 +++++++---------
 1 files changed, 7 insertions(+), 9 deletions(-)

diffs (65 lines):

diff -r bf4db7f9d867 -r 3e937b576eb2 sys/arch/amd64/include/segments.h
--- a/sys/arch/amd64/include/segments.h Fri Sep 02 08:28:06 2016 +0000
+++ b/sys/arch/amd64/include/segments.h Fri Sep 02 08:52:12 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: segments.h,v 1.27 2016/08/27 14:19:47 maxv Exp $       */
+/*     $NetBSD: segments.h,v 1.28 2016/09/02 08:52:12 maxv Exp $       */
 
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
@@ -147,7 +147,7 @@
  */
 
 /*
- * Below is used for TSS and LDT.
+ * System segment descriptor (16 bytes): used for TSS and LDT.
  */
 struct sys_segment_descriptor {
        uint64_t sd_lolimit:16; /* segment extent (lsb) */
@@ -165,7 +165,7 @@
 } __packed;
 
 /*
- * Below is used for cs, ds, etc.
+ * Memory segment descriptor (8 bytes): used for cs, ds, etc.
  */
 struct mem_segment_descriptor {
        unsigned sd_lolimit:16; /* segment extent (lsb) */
@@ -192,7 +192,7 @@
 } __packed;
 
 /*
- * Gate descriptors (e.g. indirect descriptors)
+ * Gate descriptors (16 bytes).
  */
 struct gate_descriptor {
        uint64_t gd_looffset:16;/* gate offset (lsb) */
@@ -209,7 +209,8 @@
 } __packed;
 
 /*
- * Generic descriptor
+ * Generic descriptor (8 bytes). Note: it does not include system segment
+ * descriptors and gate descriptors, since these are 16-byte-long.
  */
 union descriptor {
        struct mem_segment_descriptor sd;
@@ -218,7 +219,7 @@
 } __packed;
 
 /*
- * region descriptors, used to load gdt/idt tables before segments yet exist.
+ * Region descriptors, used to load gdt/idt tables before segments yet exist.
  */
 struct region_descriptor {
        uint16_t rd_limit;      /* segment extent */
@@ -226,9 +227,6 @@
 } __packed;
 
 #ifdef _KERNEL
-#if 0
-extern struct sys_segment_descriptor *ldt;
-#endif
 #ifdef XEN
 extern struct trap_info *idt;
 #else