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authorGeorge G. Davis <gdavis@mvista.com>2009-04-01 15:27:18 -0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2009-04-01 17:17:50 -0400
commitf2255be8126e86142901c61dd482c1c2a5ffdda7 (patch)
treea59ff8fecbbf30a7a1e33f97b59e1ed3cd38c018 /arch/arm/vfp/entry.S
parentfe68e68f6a379d317a87ae24de050a65b11ea1fb (diff)
[ARM] 5440/1: Fix VFP state corruption due to preemption during VFP exceptions
We've observed that ARM VFP state can be corrupted during VFP exception handling when PREEMPT is enabled. The exact conditions are difficult to reproduce but appear to occur during VFP exception handling when a task causes a VFP exception which is handled via VFP_bounce and is then preempted by yet another task which in turn causes yet another VFP exception. Since the VFP_bounce code is not preempt safe, VFP state then becomes corrupt. In order to prevent preemption from occuring while handling a VFP exception, this patch disables preemption while handling VFP exceptions. Signed-off-by: George G. Davis <gdavis@mvista.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/vfp/entry.S')
-rw-r--r--arch/arm/vfp/entry.S23
1 files changed, 19 insertions, 4 deletions
diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S
index ba592a9e6fb3..a2bed62aec21 100644
--- a/arch/arm/vfp/entry.S
+++ b/arch/arm/vfp/entry.S
@@ -15,13 +15,16 @@
15 * r10 = thread_info structure 15 * r10 = thread_info structure
16 * lr = failure return 16 * lr = failure return
17 */ 17 */
18#include <linux/linkage.h> 18#include <asm/thread_info.h>
19#include <linux/init.h>
20#include <asm/asm-offsets.h>
21#include <asm/assembler.h>
22#include <asm/vfpmacros.h> 19#include <asm/vfpmacros.h>
20#include "../kernel/entry-header.S"
23 21
24ENTRY(do_vfp) 22ENTRY(do_vfp)
23#ifdef CONFIG_PREEMPT
24 ldr r4, [r10, #TI_PREEMPT] @ get preempt count
25 add r11, r4, #1 @ increment it
26 str r11, [r10, #TI_PREEMPT]
27#endif
25 enable_irq 28 enable_irq
26 ldr r4, .LCvfp 29 ldr r4, .LCvfp
27 ldr r11, [r10, #TI_CPU] @ CPU number 30 ldr r11, [r10, #TI_CPU] @ CPU number
@@ -30,6 +33,12 @@ ENTRY(do_vfp)
30ENDPROC(do_vfp) 33ENDPROC(do_vfp)
31 34
32ENTRY(vfp_null_entry) 35ENTRY(vfp_null_entry)
36#ifdef CONFIG_PREEMPT
37 get_thread_info r10
38 ldr r4, [r10, #TI_PREEMPT] @ get preempt count
39 sub r11, r4, #1 @ decrement it
40 str r11, [r10, #TI_PREEMPT]
41#endif
33 mov pc, lr 42 mov pc, lr
34ENDPROC(vfp_null_entry) 43ENDPROC(vfp_null_entry)
35 44
@@ -41,6 +50,12 @@ ENDPROC(vfp_null_entry)
41 50
42 __INIT 51 __INIT
43ENTRY(vfp_testing_entry) 52ENTRY(vfp_testing_entry)
53#ifdef CONFIG_PREEMPT
54 get_thread_info r10
55 ldr r4, [r10, #TI_PREEMPT] @ get preempt count
56 sub r11, r4, #1 @ decrement it
57 str r11, [r10, #TI_PREEMPT]
58#endif
44 ldr r0, VFP_arch_address 59 ldr r0, VFP_arch_address
45 str r5, [r0] @ known non-zero value 60 str r5, [r0] @ known non-zero value
46 mov pc, r9 @ we have handled the fault 61 mov pc, r9 @ we have handled the fault