Author: cognet
Date: Sun Oct 16 17:59:28 2011
New Revision: 226443
URL: http://svn.freebsd.org/changeset/base/226443
Log:
Fix 2 bugs :
- A race condition could happen if two threads were using RAS at the same time
as the code didn't reset RAS_END, the RAS code could believe we were not in
a RAS, when we were in fact.
- Using signed value logic to compare addresses wasn't such a good idea.
Many thanks to Ian to investigate on these issues.
Pointy hat to: cognet
PR: arm/161498
Submitted by: Ian Lepore <freebsd At damnhippie DOT dyndns dot org
MFC after: 1 week
Modified:
head/sys/arm/include/asmacros.h
head/sys/arm/include/sysarch.h
Modified: head/sys/arm/include/asmacros.h
==============================================================================
--- head/sys/arm/include/asmacros.h Sun Oct 16 17:38:20 2011
(r226442)
+++ head/sys/arm/include/asmacros.h Sun Oct 16 17:59:28 2011
(r226443)
@@ -71,9 +71,8 @@
ldr r0, =ARM_RAS_START; \
mov r1, #0; \
str r1, [r0]; \
- ldr r0, =ARM_RAS_END; \
mov r1, #0xffffffff; \
- str r1, [r0];
+ str r1, [r0, #4];
/*
* PULLFRAME - macro to pull a trap frame from the stack in the current mode
@@ -120,20 +119,19 @@
stmia r0, {r13-r14}^; /* Push the user mode registers */ \
mov r0, r0; /* NOP for previous instruction */ \
ldr r5, =ARM_RAS_START; /* Check if there's any RAS */ \
- ldr r3, [r5]; \
- cmp r3, #0; /* Is the update needed ? */ \
- ldrgt lr, [r0, #16]; \
- ldrgt r1, =ARM_RAS_END; \
- ldrgt r4, [r1]; /* Get the end of the RAS */ \
- movgt r2, #0; /* Reset the magic addresses */ \
- strgt r2, [r5]; \
- movgt r2, #0xffffffff; \
- strgt r2, [r1]; \
- cmpgt lr, r3; /* Were we in the RAS ? */ \
- cmpgt r4, lr; \
- strgt r3, [r0, #16]; /* Yes, update the pc */ \
- mrs r0, spsr_all; /* Put the SPSR on the stack */ \
- str r0, [sp, #-4]!
+ ldr r4, [r5, #4]; /* reset it to point at the */ \
+ cmp r4, #0xffffffff; /* end of memory if necessary; */ \
+ movne r1, #0xffffffff; /* leave value in r4 for later */ \
+ strne r1, [r5, #4]; /* comparision against PC. */ \
+ ldr r3, [r5]; /* Retrieve global RAS_START */ \
+ cmp r3, #0; /* and reset it if non-zero. */ \
+ movne r1, #0; /* If non-zero RAS_START and */ \
+ strne r1, [r5]; /* PC was lower than RAS_END, */ \
+ ldrne r1, [r0, #16]; /* adjust the saved PC so that */ \
+ cmpne r4, r1; /* execution later resumes at */ \
+ strhi r3, [r0, #16]; /* the RAS_START location. */ \
+ mrs r0, spsr_all; \
+ str r0, [sp, #-4]!
/*
* PULLFRAMEFROMSVCANDEXIT - macro to pull a trap frame from the stack
Modified: head/sys/arm/include/sysarch.h
==============================================================================
--- head/sys/arm/include/sysarch.h Sun Oct 16 17:38:20 2011
(r226442)
+++ head/sys/arm/include/sysarch.h Sun Oct 16 17:59:28 2011
(r226443)
@@ -42,9 +42,13 @@
* 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
+ * 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.
+ * In addition, code in arm/include/atomic.h and arm/include/asmacros.h
+ * assumes that ARM_RAS_END is at ARM_RAS_START+4, so be sure to update those
+ * if ARM_RAS_END moves in relation to ARM_RAS_START (look for occurrances
+ * of ldr/str rm,[rn, #4]).
*/
#define ARM_TP_ADDRESS (ARM_VECTORS_HIGH + 0x1000)
#define ARM_RAS_START (ARM_TP_ADDRESS + 4)
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