From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from kirsty.vergenet.net ([202.4.237.240]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1W3aja-0008Bc-Su for kexec@lists.infradead.org; Thu, 16 Jan 2014 00:22:59 +0000 Date: Thu, 16 Jan 2014 09:22:34 +0900 From: Simon Horman Subject: Re: [PATCH] Fix value of mbi->mem_lower for multiboot-x86 Message-ID: <20140116002234.GC12550@verge.net.au> References: <84k3e2lyde.wl%peter.chubb@nicta.com.au> <20140115034833.GA30883@verge.net.au> <84ppntsz5x.wl%peter.chubb@nicta.com.au> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <84ppntsz5x.wl%peter.chubb@nicta.com.au> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=twosheds.infradead.org@lists.infradead.org To: Peter Chubb Cc: kexec@lists.infradead.org On Thu, Jan 16, 2014 at 08:39:06AM +1100, Peter Chubb wrote: > > In the multiboot header, there is a field, `mem_lower' that is meant to > contain the size of memory starting at zero and ending below 640k. > If your kernel is compiled with CONFIG_X86_RESERVE_LOW non zero > (the usual case), then a hole is inserted into kernel's physical > memory map at zero, so the test to find the size of this region in > kexec/arch/i386/kexec-multiboot-x86.c never succeeds, so the value is > always zero. > > On a PC99 architecture, there is always memory at physycal address zero; > assume that a region that starts below 64k actually starts at zero, > and use it for the mem_lower variable. > > Signed-off-by: Peter Chubb Thanks Peter, I have applied this. > > --- > kexec/arch/i386/kexec-multiboot-x86.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > Index: kexec-tools-2.0.4/kexec/arch/i386/kexec-multiboot-x86.c > =================================================================== > --- kexec-tools-2.0.4.orig/kexec/arch/i386/kexec-multiboot-x86.c 2013-03-14 18:45:16.000000000 +1000 > +++ kexec-tools-2.0.4/kexec/arch/i386/kexec-multiboot-x86.c 2014-01-15 10:21:02.138172304 +1000 > @@ -261,10 +261,18 @@ int multiboot_x86_load(int argc, char ** > mmap[i].length_high = length >> 32; > if (range[i].type == RANGE_RAM) { > mmap[i].Type = 1; /* RAM */ > - /* Is this the "low" memory? */ > - if ((range[i].start == 0) > - && (range[i].end > mem_lower)) > + /* > + * Is this the "low" memory? Can't just test > + * against zero, because Linux protects (and > + * hides) the first few pages of physical > + * memory. > + */ > + > + if ((range[i].start <= 64*1024) > + && (range[i].end > mem_lower)) { > + range[i].start = 0; > mem_lower = range[i].end; > + } > /* Is this the "high" memory? */ > if ((range[i].start <= 0x100000) > && (range[i].end > mem_upper + 0x100000)) > > -- > Dr Peter Chubb peter.chubb AT nicta.com.au > http://www.ssrg.nicta.com.au Software Systems Research Group/NICTA > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec