[PATCH] arm64: handle sys and undef traps consistently

[Suzuki K Poulose]

On 27/01/17 16:15, Mark Rutland wrote:
> If an EL0 instruction in the SYS class triggers an exception, do_sysintr
> looks for a sys64_hook matching the instruction, and if none is found,
> injects a SIGILL. This mirrors what we do for undefined instruction
> encodings in do_undefinstr, where we look for an undef_hook matching the
> instruction, and if none is found, inject a SIGILL.
>
> Over time, new SYS instruction encodings may be allocated. Prior to
> allocation, exceptions resulting from these would be handled by
> do_undefinstr, whereas after allocation these may be handled by
> do_sysintr.
>
> To ensure that we have consistent behaviour if and when this happens, it
> would be beneficial to have do_sysinstr fall back to do_undefinstr.
>
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Suzuki Poulose <suzuki.poulose at arm.com>
> Cc: Will Deacon <will.deacon at arm.com>
> ---
>  arch/arm64/kernel/traps.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 8187229..7c3fc06 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -531,7 +531,12 @@ asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs)
>  			return;
>  		}
>
> -	force_signal_inject(SIGILL, ILL_ILLOPC, regs, 0);
> +	/*
> +	 * New SYS instructions may previously have been undefined at EL0. Fall
> +	 * back to our usual undefined instruction handler so that we handle
> +	 * these consistently.
> +	 */
> +	do_undefinstr(regs);
>  }
>
>  long compat_arm_syscall(struct pt_regs *regs);
>

Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>