linux-kernel - Re: [PATCH 3/3] ARM: allow kernel to be loaded in middle of phymem

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]

Message-ID: <20140123193137.GA15937@n2100.arm.linux.org.uk>
Date:	Thu, 23 Jan 2014 19:31:37 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Nicolas Pitre <nico@...xnic.net>
Cc:	Wang Nan <wangnan0@...wei.com>, kexec@...ts.infradead.org,
	Eric Biederman <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Geng Hui <hui.geng@...wei.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, stable@...r.kernel.org
Subject: Re: [PATCH 3/3] ARM: allow kernel to be loaded in middle of phymem

On Thu, Jan 23, 2014 at 02:15:07PM -0500, Nicolas Pitre wrote:
> On Wed, 22 Jan 2014, Wang Nan wrote:
> 
> > This patch allows the kernel to be loaded at the middle of kernel awared
> > physical memory. Before this patch, users must use mem= or device tree to cheat
> > kernel about the start address of physical memory.
> > 
> > This feature is useful in some special cases, for example, building a crash
> > dump kernel. Without it, kernel command line, atag and devicetree must be
> > adjusted carefully, sometimes is impossible.
> 
> With CONFIG_PATCH_PHYS_VIRT the value for PHYS_OFFSET is determined 
> dynamically by rounding down the kernel image start address to the 
> previous 16MB boundary.  In the case of a crash kernel, this might be 
> cleaner to simply readjust __pv_phys_offset during early boot and call 
> fixup_pv_table(), and then reserve away the memory from the previous 
> kernel.  That will let you access that memory directly (with gdb for 
> example) and no pointer address translation will be required.

We already have support in the kernel to ignore memory below the calculated
PHYS_OFFSET.  See 571b14375019c3a66ef70d4d4a7083f4238aca30.

-- 
FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up.  Estimation
in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad.
Estimate before purchase was "up to 13.2Mbit".
--
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/