From 86a5001d4ad7111bd565d8fc4de9c231b8a9e835 Mon Sep 17 00:00:00 2001
From: Alan Jowett <alan.jowett@microsoft.com>
Date: Tue, 1 Jun 2021 16:27:25 -0600
Subject: [PATCH 1/3] Fix register mapping to avoid volatile registers and
 issues with R12

Signed-off-by: Alan Jowett <alan.jowett@microsoft.com>
---
 vm/ubpf_jit_x86_64.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/vm/ubpf_jit_x86_64.c b/vm/ubpf_jit_x86_64.c
index 6e8db798..41a833af 100644
--- a/vm/ubpf_jit_x86_64.c
+++ b/vm/ubpf_jit_x86_64.c
@@ -52,15 +52,21 @@ static int platform_parameter_registers[] = {
     RCX, RDX, R8, R9
 };
 #define RCX_ALT R15
+// Register assignments:
+// BPF R0-R4 are "volatile"
+// BPF R5-R10 are "non-volatile"
+// Map BPF volatile registers to x64 volatile and map BPF non-volatile to
+// x64 non-volatile.
+// Avoid R12 as we don't support encoding modrm modifier for using R12.
 static int register_map[REGISTER_MAP_SIZE] = {
     RAX,
     R15,
     RDX,
     R8,
     R9,
-    R10,
-    R11,
-    R12,
+    RBX,
+    RDI,
+    RSI,
     R13,
     R14,
     RBP,

From e2b41e24ee76f04c64a36454c549acab891959a7 Mon Sep 17 00:00:00 2001
From: Alan Jowett <alan.jowett@microsoft.com>
Date: Tue, 1 Jun 2021 19:04:39 -0600
Subject: [PATCH 2/3] Tweak register mapping

Signed-off-by: Alan Jowett <alan.jowett@microsoft.com>
---
 vm/ubpf_jit_x86_64.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/vm/ubpf_jit_x86_64.c b/vm/ubpf_jit_x86_64.c
index 41a833af..fb8a403b 100644
--- a/vm/ubpf_jit_x86_64.c
+++ b/vm/ubpf_jit_x86_64.c
@@ -51,7 +51,7 @@ static int platform_nonvolatile_registers[] = {
 static int platform_parameter_registers[] = {
     RCX, RDX, R8, R9
 };
-#define RCX_ALT R15
+#define RCX_ALT R10
 // Register assignments:
 // BPF R0-R4 are "volatile"
 // BPF R5-R10 are "non-volatile"
@@ -64,11 +64,11 @@ static int register_map[REGISTER_MAP_SIZE] = {
     RDX,
     R8,
     R9,
-    RBX,
+    R14,
+    R15,
     RDI,
     RSI,
-    R13,
-    R14,
+    RBX,
     RBP,
 };
 #else

From 955e51cca08fbe75b683fe213db5140468f251c4 Mon Sep 17 00:00:00 2001
From: Alan Jowett <alan.jowett@microsoft.com>
Date: Mon, 7 Jun 2021 09:01:01 -0600
Subject: [PATCH 3/3] PR feedback

Signed-off-by: Alan Jowett <alan.jowett@microsoft.com>
---
 vm/ubpf_jit_x86_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/vm/ubpf_jit_x86_64.c b/vm/ubpf_jit_x86_64.c
index fb8a403b..a9b488bf 100644
--- a/vm/ubpf_jit_x86_64.c
+++ b/vm/ubpf_jit_x86_64.c
@@ -60,7 +60,7 @@ static int platform_parameter_registers[] = {
 // Avoid R12 as we don't support encoding modrm modifier for using R12.
 static int register_map[REGISTER_MAP_SIZE] = {
     RAX,
-    R15,
+    R10,
     RDX,
     R8,
     R9,