linux-kernel - Re: [RFC] arm: Defer lookup of machine

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 12 Jan 2011 16:32:21 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Catalin Marinas <catalin.marinas@....com>,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	Nicolas Pitre <nicolas.pitre@...onical.com>
Subject: Re: [RFC] arm: Defer lookup of machine_type and vet of atags to
	setup.c

On Wed, Jan 12, 2011 at 09:24:34AM -0700, Grant Likely wrote:
> Actually it looks like the real problem is that the mmu has been
> turned on, but the virtual mappings for devices have not yet been
> established, and so the debug macros aren't using a valid address.

They should be, as they're valid for use from assembly prior to MMU
turn-on, assembly after MMU turn-on and C code.

If CONFIG_DEBUG_LL is enabled, create_page_tables() should be setting
up the necessary initial mappings for printascii() to work.

Maybe the efforts to unify that stuff ended up breaking the printascii
debugging mechanism, and we now require a new debugging mechanism to
debug the printascii debugging mechanism... :-P

I've used it on Versatile Express during the last week and it did work
right from before setup_arch() was called.

> It looks like I'd need to get past paging_init() in order to get
> ll_debug working between turning on the mmu and paging_init(), but
> paging_init() needs the mdesc pointer, and the whole point of the
> error message is that the mdesc pointer is unknown!  I don't see any
> code that sets up a debug mapping of the uart before paging_init time.

See the #ifdef CONFIG_DEBUG_LL section in create_page_tables in head.S
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/