Date: Fri, 5 Feb 1999 10:27:10 -0800 (PST) From: John Polstra <jdp@polstra.com> To: dillon@FreeBSD.ORG Cc: committers@FreeBSD.ORG Subject: Re: cvs commit: src/sys/vm vm_unix.c Message-ID: <199902051827.KAA22713@vashon.polstra.com> In-Reply-To: <199902050749.XAA35519@freefall.freebsd.org>
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In article <199902050749.XAA35519@freefall.freebsd.org>,
Matt Dillon <dillon@FreeBSD.ORG> wrote:
> dillon 1999/02/04 23:49:29 PST
>
> Modified files:
> sys/vm vm_unix.c
> Log:
> The elf loader sets the permissions on bss to VM_PROT_READ|VM_PROT_WRITE
> rather then VM_PROT_ALL. obreak, on the otherhand, uses VM_PROT_ALL.
> This prevents vm_map_insert() from being able to coalesce the heap and
> creates an extra map entry. Since current architectures ignore
> VM_PROT_EXECUTE anyway, and since not having VM_PROT_EXECUTE on data/bss
> may provide protection in the future, obreak now uses read+write rather
> then all (r+w+x).
>
> This is an optimization, not a bug fix.
>
> Submitted by: Alan Cox <alc@cs.rice.edu>
Wouldn't this change break things like just-in-time compilers, if
it weren't for the quirk that our currently-supported architectures
ignore VM_PROT_EXECUTE?
I think it would be more correct to take the opposite approach and
make the ELF loader use VM_PROT_ALL. That's what is done for a.out.
I believe the stack already needs to be VM_PROT_ALL, because of the
signal trampoline code.
I think we should change the ELF loader and RTLD to grant execute
permission whenever read permission is present. I'm willing to do
the work if there's agreement.
John
--
John Polstra jdp@polstra.com
John D. Polstra & Co., Inc. Seattle, Washington USA
"Nobody ever went broke underestimating the taste of the American public."
-- H. L. Mencken
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