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Date:   Fri, 26 Mar 2021 18:28:40 +0000
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Andrei Vagin <avagin@gmail.com>
Cc:     Will Deacon <will@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Dave Martin <Dave.Martin@arm.com>,
        Keno Fischer <keno@juliacomputing.com>
Subject: Re: [PATCH 1/4] arm64: expose orig_x0 in the user_pt_regs structure
Message-ID: <20210326182839.GE5126@arm.com>
References: <20210322225053.428615-1-avagin@gmail.com>
 <20210322225053.428615-2-avagin@gmail.com>
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On Mon, Mar 22, 2021 at 03:50:50PM -0700, Andrei Vagin wrote:
> diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
> index 758ae984ff97..3c118c5b0893 100644
> --- a/arch/arm64/include/uapi/asm/ptrace.h
> +++ b/arch/arm64/include/uapi/asm/ptrace.h
> @@ -90,6 +90,7 @@ struct user_pt_regs {
>  	__u64		sp;
>  	__u64		pc;
>  	__u64		pstate;
> +	__u64		orig_x0;
>  };

That's a UAPI change, likely to go wrong. For example, a
ptrace(PTRACE_GETREGSET, pid, REGSET_GPR, data) would write past the end
of an old struct user_pt_regs in the debugger.

-- 
Catalin