From 9c9b3a5e3d7dcd576dfaf0dda0e86b5c8ec4e109 Mon Sep 17 00:00:00 2001
From: Giacomo Travaglini <giacomo.travaglini@arm.com>
Date: Fri, 8 Apr 2022 13:03:03 +0100
Subject: [PATCH] arch-arm: Split purifyTaggedAddr in two sub-functions

This patch is splitting the purifyTaggedAddr helper in two
by introducing the maskTaggedAddress utility

* The first part computes the top bit of the address (computeAddrTop)
(This is required as the MSBs of a VA could be used to store
tags like in FEAT_Pauth)

* The second part applies some masking to the supplied
address (maskTaggedAddress) depending on the top bit to
purify the VA from the TAG

The motivation of this split will be clear in the next patch:
we want to memoize the expensive computeAddrTop. Memoizing
purifyTaggedAddr is inefficient as the first argument
is the VA of the memory request so multiple memory requests
will allocate multiple entries in the results cache and
memoization will rarely be used.

We will memoize the VA agnostic computeAddrTop instead

Change-Id: Ib3d8bb521be67a1f21c0891e753396299adf500b
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59150
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
---
 src/arch/arm/utility.cc | 26 +++++++++++++++++---------
 src/arch/arm/utility.hh |  4 +++-
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/src/arch/arm/utility.cc b/src/arch/arm/utility.cc
index 6852aede22..d9649a6337 100644
--- a/src/arch/arm/utility.cc
+++ b/src/arch/arm/utility.cc
@@ -469,6 +469,22 @@ computeAddrTop(ThreadContext *tc, bool selbit, bool is_instr,
     int res = (tbi && (!tbid || !is_instr))? 55: 63;
     return res;
 }
+
+Addr
+maskTaggedAddr(Addr addr, ThreadContext *tc, ExceptionLevel el,
+               int topbit)
+{
+    if (topbit == 63) {
+        return addr;
+    } else if (bits(addr,55) && (el <= EL1 || ELIsInHost(tc, el))) {
+        uint64_t mask = ((uint64_t)0x1 << topbit) -1;
+        addr = addr | ~mask;
+    } else {
+        addr = bits(addr, topbit, 0);
+    }
+    return addr;  // Nothing to do if this is not a tagged address
+}
+
 Addr
 purifyTaggedAddr(Addr addr, ThreadContext *tc, ExceptionLevel el,
                  TCR tcr, bool is_instr)
@@ -476,15 +492,7 @@ purifyTaggedAddr(Addr addr, ThreadContext *tc, ExceptionLevel el,
     bool selbit = bits(addr, 55);
     int topbit = computeAddrTop(tc, selbit, is_instr, tcr, el);
 
-    if (topbit == 63) {
-        return addr;
-    } else if (selbit && (el == EL1 || el == EL0 || ELIsInHost(tc, el))) {
-        uint64_t mask = ((uint64_t)0x1 << topbit) -1;
-        addr = addr | ~mask;
-    } else {
-        addr = bits(addr, topbit, 0);
-    }
-    return addr;  // Nothing to do if this is not a tagged address
+    return maskTaggedAddr(addr, tc, el, topbit);
 }
 
 Addr
diff --git a/src/arch/arm/utility.hh b/src/arch/arm/utility.hh
index 00b0acf383..523061b706 100644
--- a/src/arch/arm/utility.hh
+++ b/src/arch/arm/utility.hh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2012-2013, 2016-2020 ARM Limited
+ * Copyright (c) 2010, 2012-2013, 2016-2020, 2022 Arm Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -207,6 +207,8 @@ Addr purifyTaggedAddr(Addr addr, ThreadContext *tc, ExceptionLevel el,
                       TCR tcr, bool isInstr);
 Addr purifyTaggedAddr(Addr addr, ThreadContext *tc, ExceptionLevel el,
                       bool isInstr);
+Addr maskTaggedAddr(Addr addr, ThreadContext *tc, ExceptionLevel el,
+                    int topbit);
 int computeAddrTop(ThreadContext *tc, bool selbit, bool isInstr,
                    TCR tcr, ExceptionLevel el);