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

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Message-ID: <e5e4ccc4b652ca65a9a02288060c46b9@mx.sdfeu.org>
Date:   Mon, 27 Mar 2017 20:55:00 +0200
From:   none <ytrezq@...-eu.org>
To:     Richard Weinberger <richard.weinberger@...il.com>
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

Le 2017-03-27 17:30, Richard Weinberger a écrit :
> 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.

Sorry but so, in the case of x86_64, which is the struct member I need 
to look at ?