linux-kernel - Re: Getting the way a SIGSEGV append when catching a SIGSEGV from within

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Message-ID: <CAFLxGvzC_63RkxgTNnG8g2Hw5CUW7SVLuUMuE7_13Dw1bqHUUA@mail.gmail.com>
Date:   Mon, 27 Mar 2017 17:30:32 +0200
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     none <ytrezq@...-eu.org>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-x86_64@...r.kernel.org
Subject: Re: Getting the way a SIGSEGV append when catching a SIGSEGV from within

On Mon, Mar 27, 2017 at 4:45 PM, none <ytrezq@...-eu.org> wrote:
> Hello,
>
> There’s three way to perform an invalid memory access :
>
> The attempt to execute/jump at an invalid address.
> The attempt to read at an invalid address.
> The attempt to write at an invalid address.
>
> Determining the execute case with rt_sigaction is easy : the last value of
> eip match the value of the address which caused the segfault.
>
> But how to know if the SIGSEGV occurred by a read or by a write attempt ? In
> the same time shouldn’t that information belong in the mmu ?

Did you look at the machine specific context of SIGSEGV?
It will give you access to the error code and the trap number.

-- 
Thanks,
//richard