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From: Florian Weimer <fweimer@redhat.com>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Joel Molin via Libc-help <libc-help@sourceware.org>,
	 Joel Molin <joelmolin@gmail.com>
Subject: Re: Why does _dl_protect_relro align the end address down?
Date: Tue, 17 Jan 2023 15:16:42 +0100	[thread overview]
Message-ID: <878ri15jqt.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <6b782360-131f-df4c-9dc4-6765d0fb8c24@linaro.org> (Adhemerval Zanella Netto's message of "Tue, 17 Jan 2023 11:11:10 -0300")

* Adhemerval Zanella Netto:

> On 17/01/23 04:57, Florian Weimer via Libc-help wrote:
>> * Joel Molin via Libc-help:
>> 
>>> Since mprotect will protect entire pages anyway, wouldn't it make a lot
>>> more sense here to say `end = ALIGN_UP(...)`? Apart from feeling more
>>> intuitive, it also seems like it would avoid page size inconsistencies
>>> between runtime and link editing like the one above.
>> 
>> ALIGN_UP might make memory read-only that should not be.
>> 
>> There's some discussion about the alignment here:
>> 
>>   PT_GNU_RELRO is somewhat broken
>>   <https://sourceware.org/pipermail/libc-alpha/2022-May/138638.html>
>> 
>> I still think this is fairly broken, but there does not seem to be much
>> desire to fix it.
>
> It was not clear to me from that discussion what you think it is still
> broken with PT_GNU_RELRO.

Using ALIGN_DOWN for the start address can't be right.

Thanks,
Florian


  reply	other threads:[~2023-01-17 14:16 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-16 21:26 Joel Molin
2023-01-17  7:57 ` Florian Weimer
2023-01-17 14:11   ` Adhemerval Zanella Netto
2023-01-17 14:16     ` Florian Weimer [this message]
2023-01-17 14:30       ` Adhemerval Zanella Netto
2023-01-17 15:48         ` H.J. Lu
2023-01-17 15:56           ` Joel Molin

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