x86: Add bitfields which can gather/scatter bases and limits.

Add bitfields which can gather/scatter base and limit fields within
"normal" segment descriptors, and in TSS descriptors which have the
same bitfields in the same positions for those two values.

This centralizes the code which manages those bitfields and makes it
less likely that a local implementation will be buggy.

Change-Id: I9809aa626fc31388595c3d3b225c25a0ec6a1275
Reviewed-on: https://gem5-review.googlesource.com/7661
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

1 files changed, 6 insertions, 14 deletions

diff --git a/src/arch/x86/process.cc b/src/arch/x86/process.cc
index cfec21f39..7c979c016 100644
--- a/src/arch/x86/process.cc
+++ b/src/arch/x86/process.cc
@@ -244,12 +244,9 @@ X86_64Process::initState()
         initDesc.p = 1;               // present
         initDesc.l = 1;               // longmode - 64 bit
         initDesc.d = 0;               // operand size
-        initDesc.g = 1;               // granularity
         initDesc.s = 1;               // system segment
-        initDesc.limitHigh = 0xFFFF;
-        initDesc.limitLow = 0xF;
-        initDesc.baseHigh = 0x0;
-        initDesc.baseLow = 0x0;
+        initDesc.limit = 0xFFFFFFFF;
+        initDesc.base = 0;
 
         //64 bit code segment
         SegDescriptor csLowPLDesc = initDesc;
@@ -320,11 +317,8 @@ X86_64Process::initState()
         TSSDescLow.type = 0xB;
         TSSDescLow.dpl = 0; // Privelege level 0
         TSSDescLow.p = 1; // Present
-        TSSDescLow.g = 1; // Page granularity
-        TSSDescLow.limitHigh = 0xF;
-        TSSDescLow.limitLow = 0xFFFF;
-        TSSDescLow.baseLow = bits(TSSVirtAddr, 23, 0);
-        TSSDescLow.baseHigh = bits(TSSVirtAddr, 31, 24);
+        TSSDescLow.limit = 0xFFFFFFFF;
+        TSSDescLow.base = bits(TSSVirtAddr, 31, 0);
 
         TSShigh TSSDescHigh = 0;
         TSSDescHigh.base = bits(TSSVirtAddr, 63, 32);
@@ -342,10 +336,8 @@ X86_64Process::initState()
         SegSelector tssSel = 0;
         tssSel.si = numGDTEntries - 1;
 
-        uint64_t tss_base_addr = (TSSDescHigh.base << 32) |
-                                 (TSSDescLow.baseHigh << 24) |
-                                  TSSDescLow.baseLow;
-        uint64_t tss_limit = TSSDescLow.limitLow | (TSSDescLow.limitHigh << 16);
+        uint64_t tss_base_addr = (TSSDescHigh.base << 32) | TSSDescLow.base;
+        uint64_t tss_limit = TSSDescLow.limit;
 
         SegAttr tss_attr = 0;