From a43268a7464c3240c1d9b860bd32d4f656a6dfea Mon Sep 17 00:00:00 2001
From: Olivier Houchard <cognet@FreeBSD.org>
Date: Thu, 12 Feb 2009 23:23:30 +0000
Subject: [PATCH] To prevent various race conditions in the RAS code, store and
 restore the values in ARM_RAS_START and ARM_RAS_END at context switch time.

MFC after:	1 week
---
 sys/arm/arm/genassym.c    |  2 ++
 sys/arm/arm/swtch.S       | 20 ++++++++++++++++----
 sys/arm/include/proc.h    |  2 ++
 sys/arm/include/sysarch.h |  3 +++
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/sys/arm/arm/genassym.c b/sys/arm/arm/genassym.c
index ba75886490e..40b29883bda 100644
--- a/sys/arm/arm/genassym.c
+++ b/sys/arm/arm/genassym.c
@@ -96,6 +96,8 @@ ASSYM(TD_FRAME, offsetof(struct thread, td_frame));
 ASSYM(TD_MD, offsetof(struct thread, td_md));
 ASSYM(TD_LOCK, offsetof(struct thread, td_lock));
 ASSYM(MD_TP, offsetof(struct mdthread, md_tp));
+ASSYM(MD_RAS_START, offsetof(struct mdthread, md_ras_start));
+ASSYM(MD_RAS_END, offsetof(struct mdthread, md_ras_end));
 
 ASSYM(TF_R0, offsetof(struct trapframe, tf_r0));
 ASSYM(TF_R1, offsetof(struct trapframe, tf_r1));
diff --git a/sys/arm/arm/swtch.S b/sys/arm/arm/swtch.S
index 8f0f9b26571..e1641960e4a 100644
--- a/sys/arm/arm/swtch.S
+++ b/sys/arm/arm/swtch.S
@@ -205,8 +205,12 @@ ENTRY(cpu_throw)
 
 	/* Set the new tp */
 	ldr	r6, [r5, #(TD_MD + MD_TP)]
-	ldr	r5, =ARM_TP_ADDRESS
-	strt	r6, [r5]
+	ldr	r4, =ARM_TP_ADDRESS
+	str	r6, [r4]
+	ldr	r6, [r5, #(TD_MD + MD_RAS_START)]
+	str	r6, [r4, #4] /* ARM_RAS_START */
+	ldr	r6, [r5, #(TD_MD + MD_RAS_END)]
+	str	r6, [r4, #4] /* ARM_RAS_END */
 
 	/* Hook in a new pcb */
 	ldr	r6, .Lcurpcb
@@ -265,12 +269,20 @@ ENTRY(cpu_switch)
 	 */
 	/* Store the old tp */
 	ldr	r3, =ARM_TP_ADDRESS
-	ldrt	r9, [r3]
+	ldr	r9, [r3]
 	str	r9, [r0, #(TD_MD + MD_TP)]
+	ldr	r9, [r3, #4]
+	str	r9, [r0, #(TD_MD + MD_RAS_START)]
+	ldr	r9, [r3, #8]
+	str	r9, [r0, #(TD_MD + MD_RAS_END)]
 
 	/* Set the new tp */
 	ldr	r9, [r1, #(TD_MD + MD_TP)]
-	strt	r9, [r3]
+	str	r9, [r3]
+	ldr	r9, [r1, #(TD_MD + MD_RAS_START)]
+	str	r9, [r3, #4]
+	ldr	r9, [r1, #(TD_MD + MD_RAS_END)]
+	str	r9, [r3, #8]
 
 	/* Get the user structure for the new process in r9 */
 	ldr	r9, [r1, #(TD_PCB)]
diff --git a/sys/arm/include/proc.h b/sys/arm/include/proc.h
index 597c75ceaed..c7b2a4ef5c9 100644
--- a/sys/arm/include/proc.h
+++ b/sys/arm/include/proc.h
@@ -51,6 +51,8 @@ struct mdthread {
 	int md_ptrace_instr;
 	int md_ptrace_addr;
 	void *md_tp;
+	void *md_ras_start;
+	void *md_ras_end;
 };
 
 struct mdproc {
diff --git a/sys/arm/include/sysarch.h b/sys/arm/include/sysarch.h
index 5623fd72f1e..12db4df6e24 100644
--- a/sys/arm/include/sysarch.h
+++ b/sys/arm/include/sysarch.h
@@ -42,6 +42,9 @@
  * The ARM_TP_ADDRESS points to a special purpose page, which is used as local
  * store for the ARM per-thread data and Restartable Atomic Sequences support.
  * Put it just above the "high" vectors' page.
+ * the cpu_switch() code assumes ARM_RAS_START is ARM_TP_ADDRESS + 4, and
+ * ARM_RAS_END is ARM_TP_ADDRESS + 8, so if that ever changes, be sure to
+ * update the cpu_switch() (and cpu_throw()) code as well.
  */
 #define ARM_TP_ADDRESS		(ARM_VECTORS_HIGH + 0x1000)
 #define ARM_RAS_START		(ARM_TP_ADDRESS + 4)