From 03ce84ec01f99b3d5a86d1fd505f732091879e3e Mon Sep 17 00:00:00 2001
From: Vinayak Menon <vinayakm.list@gmail.com>
Date: Fri, 17 Apr 2020 19:41:27 +0530
Subject: [PATCH 1/4] fix the arm64 vtop and ptov calculations

Linux kernel patch "arm64: mm: Introduce vabits_actual" introduced
physvirt_offset which is not equal to PHYS_OFFSET - PAGE_OFFSET
when kaslr is enabled. physvirt_offset is caculated in arch/arm64/mm/init.c
before memstart_addr (PHYS_OFFSET) is randomized. Let vtop and ptov use
physvirt_offset instead, whose default value is set to (phys_offset - page_offset)

---
 arm64.c | 36 +++++++++++++++++++++++++++++++++---
 defs.h  |  3 ++-
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/arm64.c b/arm64.c
index 09b1b76..7a05f2a 100644
--- a/arm64.c
+++ b/arm64.c
@@ -31,6 +31,7 @@ static int arm64_search_for_kimage_voffset(ulong);
 static int verify_kimage_voffset(void);
 static void arm64_calc_kimage_voffset(void);
 static void arm64_calc_phys_offset(void);
+static void arm64_calc_physvirt_offset(void);
 static void arm64_calc_virtual_memory_ranges(void);
 static void arm64_get_section_size_bits(void);
 static int arm64_kdump_phys_base(ulong *);
@@ -362,6 +363,8 @@ arm64_init(int when)
 
 		/* use machdep parameters */
 		arm64_calc_phys_offset();
+		/* call this after setting phys_offset and page_offset */
+		arm64_calc_physvirt_offset();
 	
 		if (CRASHDEBUG(1)) {
 			if (machdep->flags & NEW_VMEMMAP)
@@ -474,6 +477,7 @@ arm64_init(int when)
 		arm64_calc_VA_BITS();
 		arm64_calc_phys_offset();
 		machdep->machspec->page_offset = ARM64_PAGE_OFFSET;
+		arm64_calc_physvirt_offset();
 		break;
 	}
 }
@@ -967,6 +971,28 @@ arm64_calc_kimage_voffset(void)
 }
 
 static void
+arm64_calc_physvirt_offset(void)
+{
+	struct machine_specific *ms = machdep->machspec;
+	ulong physvirt_offset;
+	struct syment *sp;
+
+	ms->physvirt_offset = ms->phys_offset - ms->page_offset;
+
+	if ((sp = kernel_symbol_search("physvirt_offset")) &&
+			machdep->machspec->kimage_voffset) {
+		if (READMEM(pc->mfd, &physvirt_offset, sizeof(physvirt_offset),
+			sp->value, sp->value -
+			machdep->machspec->kimage_voffset) > 0) {
+				ms->physvirt_offset = physvirt_offset;
+		}
+	}
+
+	if (CRASHDEBUG(1))
+		fprintf(fp, "using %lx as physvirt_offset\n", ms->physvirt_offset);
+}
+
+static void
 arm64_calc_phys_offset(void)
 {
 	struct machine_specific *ms = machdep->machspec;
@@ -1147,9 +1173,13 @@ arm64_VTOP(ulong addr)
 			return addr - machdep->machspec->kimage_voffset;
 		}
 
-		if (addr >= machdep->machspec->page_offset)
-			return machdep->machspec->phys_offset
-				+ (addr - machdep->machspec->page_offset);
+		if (addr >= machdep->machspec->page_offset) {
+			if (machdep->machspec->physvirt_offset)
+				return addr + machdep->machspec->physvirt_offset;
+			else
+				return machdep->machspec->phys_offset
+					+ (addr - machdep->machspec->page_offset);
+		}
 		else if (machdep->machspec->kimage_voffset)
 			return addr - machdep->machspec->kimage_voffset;
 		else /* no randomness */
diff --git a/defs.h b/defs.h
index 923869c..b53562e 100644
--- a/defs.h
+++ b/defs.h
@@ -3030,7 +3030,7 @@ typedef u64 pte_t;
 #define MACHINE_TYPE       "ARM64"    
 
 #define PTOV(X) \
-	((unsigned long)(X)-(machdep->machspec->phys_offset)+(machdep->machspec->page_offset))
+	((unsigned long)(X) - (machdep->machspec->physvirt_offset))
 
 #define VTOP(X)               arm64_VTOP((ulong)(X))
 
@@ -3280,6 +3280,7 @@ struct machine_specific {
 	ulong VA_BITS_ACTUAL;
 	ulong CONFIG_ARM64_VA_BITS;
 	ulong VA_START;
+	ulong physvirt_offset;
 };
 
 struct arm64_stackframe {
--