From 15df63624bc915b265c89666d09cb908a19c8d74 Mon Sep 17 00:00:00 2001
From: Gabe Black <gabe.black@gmail.com>
Date: Sun, 9 Jan 2022 01:47:57 -0800
Subject: [PATCH] arch-x86: Add some DPRINTFs to the TLB.

These DPRINTFs are related to segmentation handling when in 32 bit
protected mode.

Change-Id: I47eb2bc834fc748b5d01d85e02ea8b3f6e03091b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55246
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/arch/x86/tlb.cc | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/arch/x86/tlb.cc b/src/arch/x86/tlb.cc
index b2856edc80..7d20e004da 100644
--- a/src/arch/x86/tlb.cc
+++ b/src/arch/x86/tlb.cc
@@ -334,16 +334,23 @@ TLB::translate(const RequestPtr &req,
         // If we're not in 64-bit mode, do protection/limit checks
         if (m5Reg.mode != LongMode) {
             DPRINTF(TLB, "Not in long mode. Checking segment protection.\n");
+
             SegAttr attr = tc->readMiscRegNoEffect(MISCREG_SEG_ATTR(seg));
             // Check for an unusable segment.
-            if (attr.unusable)
+            if (attr.unusable) {
+                DPRINTF(TLB, "Unusable segment.\n");
                 return std::make_shared<GeneralProtection>(0);
+            }
             bool expandDown = false;
             if (seg >= SEGMENT_REG_ES && seg <= SEGMENT_REG_HS) {
-                if (!attr.writable && (mode == BaseMMU::Write || storeCheck))
+                if (!attr.writable && (mode == BaseMMU::Write || storeCheck)) {
+                    DPRINTF(TLB, "Tried to write to unwritable segment.\n");
                     return std::make_shared<GeneralProtection>(0);
-                if (!attr.readable && mode == BaseMMU::Read)
+                }
+                if (!attr.readable && mode == BaseMMU::Read) {
+                    DPRINTF(TLB, "Tried to read from unreadble segment.\n");
                     return std::make_shared<GeneralProtection>(0);
+                }
                 expandDown = attr.expandDown;
 
             }
@@ -361,8 +368,11 @@ TLB::translate(const RequestPtr &req,
                 if (offset <= limit || endOffset <= limit)
                     return std::make_shared<GeneralProtection>(0);
             } else {
-                if (offset > limit || endOffset > limit)
+                if (offset > limit || endOffset > limit) {
+                    DPRINTF(TLB, "Segment limit check failed, "
+                            "offset = %#x limit = %#x.\n", offset, limit);
                     return std::make_shared<GeneralProtection>(0);
+                }
             }
         }
         if (m5Reg.submode != SixtyFourBitMode ||