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arm64: neon: Forbid when irqs are disabled

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Currently, may_use_simd() can return true if IRQs are disabled.  If
the caller goes ahead and calls kernel_neon_begin(), this can
result in use of local_bh_enable() in an unsafe context.

In particular, __efi_fpsimd_begin() may do this when calling EFI as
part of system shutdown.

This patch ensures that callers don't think they can use
kernel_neon_begin() in such a context.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Dave Martin 2017-08-09 11:43:28 +01:00 committed by Catalin Marinas
parent 11cefd5ac2
commit 66c3ec5a71
1 changed files with 3 additions and 1 deletions
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4
arch/arm64/include/asm/simd.h
View file

@ -10,6 +10,7 @@
#define __ASM_SIMD_H
#include <linux/compiler.h>
#include <linux/irqflags.h>
#include <linux/percpu.h>
#include <linux/preempt.h>
#include <linux/types.h>
@ -40,7 +41,8 @@ static __must_check inline bool may_use_simd(void)
* can't migrate to another CPU and spuriously see it become
* false.
*/
return !in_irq() && !in_nmi() && !raw_cpu_read(kernel_neon_busy);
return !in_irq() && !irqs_disabled() && !in_nmi() &&
!raw_cpu_read(kernel_neon_busy);
}
#else /* ! CONFIG_KERNEL_MODE_NEON */