f2255be812
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>
68 lines
1.6 KiB
ArmAsm
68 lines
1.6 KiB
ArmAsm
/*
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* linux/arch/arm/vfp/entry.S
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*
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* Copyright (C) 2004 ARM Limited.
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* Written by Deep Blue Solutions Limited.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Basic entry code, called from the kernel's undefined instruction trap.
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* r0 = faulted instruction
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* r5 = faulted PC+4
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* r9 = successful return
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* r10 = thread_info structure
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* lr = failure return
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*/
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#include <asm/thread_info.h>
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#include <asm/vfpmacros.h>
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#include "../kernel/entry-header.S"
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ENTRY(do_vfp)
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#ifdef CONFIG_PREEMPT
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ldr r4, [r10, #TI_PREEMPT] @ get preempt count
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add r11, r4, #1 @ increment it
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str r11, [r10, #TI_PREEMPT]
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#endif
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enable_irq
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ldr r4, .LCvfp
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ldr r11, [r10, #TI_CPU] @ CPU number
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add r10, r10, #TI_VFPSTATE @ r10 = workspace
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ldr pc, [r4] @ call VFP entry point
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ENDPROC(do_vfp)
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ENTRY(vfp_null_entry)
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#ifdef CONFIG_PREEMPT
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get_thread_info r10
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ldr r4, [r10, #TI_PREEMPT] @ get preempt count
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sub r11, r4, #1 @ decrement it
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str r11, [r10, #TI_PREEMPT]
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#endif
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mov pc, lr
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ENDPROC(vfp_null_entry)
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.LCvfp:
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.word vfp_vector
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@ This code is called if the VFP does not exist. It needs to flag the
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@ failure to the VFP initialisation code.
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__INIT
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ENTRY(vfp_testing_entry)
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#ifdef CONFIG_PREEMPT
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get_thread_info r10
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ldr r4, [r10, #TI_PREEMPT] @ get preempt count
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sub r11, r4, #1 @ decrement it
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str r11, [r10, #TI_PREEMPT]
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#endif
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ldr r0, VFP_arch_address
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str r5, [r0] @ known non-zero value
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mov pc, r9 @ we have handled the fault
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ENDPROC(vfp_testing_entry)
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VFP_arch_address:
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.word VFP_arch
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__FINIT
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