Hi,
shouldn't be on libc-alpha, I guess. It's just noise for most of the people
there.
On Sun, Nov 03, 2002 at 11:29:33AM -0500, James A Morrison wrote:
> I was looking at why gpg fails to build on the Hurd. I discovered mlock
> is what is broken.
Without really going into your patch, here is some background noise from the
past. Here is what Roland wrote a long time ago:
"This might be a known kernel problem, I'm just a bit sketchy on the details.
That is, the Hurd code that does wiring (libshouldbeinlibc/wire.c) makes
the pages writable and pokes them before doing vm_wire.
It seems like a breach of the supposed kernel interface of vm_wire that you
should have to do this (vm_wire should just force all the copies it needs
to), but that is the way the kernel is. At least I think so, but I am not
entirely sure I am right about the situation in the kernel."
He also suggested:
"It would be cool if you could step through vm_wire using gdb on oskit-mach
and figure out where specifically it fails."
Thomas replied to the above first paragaph:
"This is because there were kernel bugs if you get a pagein on wired
memory. That is, the kernel assumes that wired memory is *already* in
core. The little poking routine is to do our best to make sure we
don't have that problem."
> The problem arises when the actual protection on the
> memory is less relaxed than the protection passed to vm_wire. What does work
> is using VM_PROT_DEFAULT, because memory allocated with malloc seems to use
> VM_PROT_DEFAULT. However, I think the best solution is to call vm_region
> and actually get the proper permissions for the pages.
>
> Here are a couple of patches that checks vm_region and acts more like
> wire_segment_internal in [hurd]/libshouldbeinlibc. The first patch relaxes
> the permissions on the memory region to max_protection so that the wired
> region can have its protections relaxed to that level at any time. The
> second does not because perhaps something could write to a read-only part
> of memory between the calls to vm_protect.
>
> 2002-11-03 James Morrison <[EMAIL PROTECTED]>
>
> * sysdeps/mach/hurd/mlock.c (mlock): Get the actual protections on a
> region of memory before wiring it.
>
> Index: mlock.c
> ===================================================================
> RCS file: /cvs/glibc/libc/sysdeps/mach/hurd/mlock.c,v
> retrieving revision 1.2
> diff -u -r1.2 mlock.c
> --- mlock.c 6 Jul 2001 04:55:57 -0000 1.2
> +++ mlock.c 3 Nov 2002 16:18:09 -0000
> @@ -39,8 +39,19 @@
>
> page = trunc_page ((vm_address_t) addr);
> len = round_page ((vm_address_t) addr + len) - page;
> - err = __vm_wire (hostpriv, __mach_task_self (), page, len,
> - VM_PROT_ALL); /* XXX ? */
> + {
> + vm_prot_t cur, max;
> + vm_inherit_t inher;
> + boolean_t shared;
> + mach_port_t obj;
> + vm_offset_t offs;
> +
> + __vm_region (mach_task_self (), &page, &len, &cur, &max, &inher, &shared,
> + &obj, &offs);
> + __vm_protect (mach_task_self (), page, len, 0, max);
> + err = __vm_wire (hostpriv, __mach_task_self (), page, len, max);
> + __vm_protect (mach_task_self (), page, len, 0, cur);
> + }
> __mach_port_deallocate (__mach_task_self (), hostpriv);
>
> return err ? __hurd_fail (err) : 0;
>
> Index: mlock.c
> ===================================================================
> RCS file: /cvs/glibc/libc/sysdeps/mach/hurd/mlock.c,v
> retrieving revision 1.2
> diff -u -r1.2 mlock.c
> --- mlock.c 6 Jul 2001 04:55:57 -0000 1.2
> +++ mlock.c 3 Nov 2002 16:25:44 -0000
> @@ -39,8 +39,18 @@
>
> page = trunc_page ((vm_address_t) addr);
> len = round_page ((vm_address_t) addr + len) - page;
> - err = __vm_wire (hostpriv, __mach_task_self (), page, len,
> - VM_PROT_ALL); /* XXX ? */
> + {
> + vm_prot_t cur, max;
> + vm_inherit_t inher;
> + boolean_t shared;
> + mach_port_t obj;
> + vm_offset_t offs;
> +
> + __vm_region (mach_task_self (), &page, &len, &cur, &max, &inher, &shared,
> + &obj, &offs);
> + err = __vm_wire (hostpriv, __mach_task_self (), page, len, max);
> + __mach_port_deallocate (mach_task_self (), obj);
> + }
> __mach_port_deallocate (__mach_task_self (), hostpriv);
>
> return err ? __hurd_fail (err) : 0;
>
--
`Rhubarb is no Egyptian god.' GNU http://www.gnu.org [EMAIL PROTECTED]
Marcus Brinkmann The Hurd http://www.gnu.org/software/hurd/
[EMAIL PROTECTED]
http://www.marcus-brinkmann.de/
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