From: "'Milton Miller'" <miltonm@bga.com> To: Dave Carroll <dcarroll@astekcorp.com> Cc: Paul Mackerras <paulus@samba.org>, LPPC <linuxppc-dev@lists.ozlabs.org>, LKML <linux-kernel@vger.kernel.org>, "Benjamin Herrenschmidt" <benh@kernel.crashing.org> Subject: Re: [PATCH v3] powerpc: Force page alignment for initrd reserved memory Subject: Re: [PATCH v3] powerpc: Force page alignment for initrd reserved memory Date: Sun, 22 May 2011 16:17:18 -0500 [thread overview] Message-ID: <initrd-reserve-reply2@mdm.bga.com> (raw) In-Reply-To: <522F24EF533FC546962ECFA2054FF777373072AB73@MAILSERVER2.cos.astekcorp.com> On Sat, 21 May 2011 about 11:05:27 -0600, Dave Carroll wrote: > > When using 64K pages with a separate cpio rootfs, U-Boot will align > the rootfs on a 4K page boundary. When the memory is reserved, and > subsequent early memblock_alloc is called, it will allocate memory > between the 64K page alignment and reserved memory. When the reserved > memory is subsequently freed, it is done so by pages, causing the > early memblock_alloc requests to be re-used, which in my case, caused > the device-tree to be clobbered. > > This patch forces the reserved memory for initrd to be kernel page > aligned, and adds the same range extension when freeing initrd. Getting better, but > > > Signed-off-by: Dave Carroll <dcarroll@astekcorp.com> > --- > arch/powerpc/kernel/prom.c | 4 +++- > arch/powerpc/mm/init_32.c | 3 +++ > arch/powerpc/mm/init_64.c | 3 +++ > 3 files changed, 9 insertions(+), 1 deletions(-) > > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c > index 48aeb55..397d4a0 100644 > --- a/arch/powerpc/kernel/prom.c > +++ b/arch/powerpc/kernel/prom.c > @@ -555,7 +555,9 @@ static void __init early_reserve_mem(void) > #ifdef CONFIG_BLK_DEV_INITRD > /* then reserve the initrd, if any */ > if (initrd_start && (initrd_end > initrd_start)) Here you test the unaligned values > void free_initrd_mem(unsigned long start, unsigned long end) > { > + start = _ALIGN_DOWN(start, PAGE_SIZE); > + end = _ALIGN_UP(end, PAGE_SIZE); > + > if (start < end) > printk ("Freeing initrd memory: %ldk freed\n", (end - start) >> 10); But here you test the aligned values. And they are aligned with opposite bias. Which means that if start == end (or is less than, but within the same page), a page that wasn't reserved (same 32 and 64 bit) gets freed. I thought "what happens if we are within a page of end, could we free the last page of bss?", but then I checked vmlinux.lds and we align end to page size. I thought other allocations should be safe, but then remembered: The flattened device tree (of which we continue to use the string table after boot) could be a problem. milton
WARNING: multiple messages have this Message-ID (diff)
From: 'Milton Miller' <miltonm@bga.com> To: Dave Carroll <dcarroll@astekcorp.com> Cc: LPPC <linuxppc-dev@lists.ozlabs.org>, Paul Mackerras <paulus@samba.org>, LKML <linux-kernel@vger.kernel.org> Subject: Re: [PATCH v3] powerpc: Force page alignment for initrd reserved memory Subject: Re: [PATCH v3] powerpc: Force page alignment for initrd reserved memory Date: Sun, 22 May 2011 16:17:18 -0500 [thread overview] Message-ID: <initrd-reserve-reply2@mdm.bga.com> (raw) In-Reply-To: <522F24EF533FC546962ECFA2054FF777373072AB73@MAILSERVER2.cos.astekcorp.com> On Sat, 21 May 2011 about 11:05:27 -0600, Dave Carroll wrote: > > When using 64K pages with a separate cpio rootfs, U-Boot will align > the rootfs on a 4K page boundary. When the memory is reserved, and > subsequent early memblock_alloc is called, it will allocate memory > between the 64K page alignment and reserved memory. When the reserved > memory is subsequently freed, it is done so by pages, causing the > early memblock_alloc requests to be re-used, which in my case, caused > the device-tree to be clobbered. > > This patch forces the reserved memory for initrd to be kernel page > aligned, and adds the same range extension when freeing initrd. Getting better, but > > > Signed-off-by: Dave Carroll <dcarroll@astekcorp.com> > --- > arch/powerpc/kernel/prom.c | 4 +++- > arch/powerpc/mm/init_32.c | 3 +++ > arch/powerpc/mm/init_64.c | 3 +++ > 3 files changed, 9 insertions(+), 1 deletions(-) > > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c > index 48aeb55..397d4a0 100644 > --- a/arch/powerpc/kernel/prom.c > +++ b/arch/powerpc/kernel/prom.c > @@ -555,7 +555,9 @@ static void __init early_reserve_mem(void) > #ifdef CONFIG_BLK_DEV_INITRD > /* then reserve the initrd, if any */ > if (initrd_start && (initrd_end > initrd_start)) Here you test the unaligned values > void free_initrd_mem(unsigned long start, unsigned long end) > { > + start = _ALIGN_DOWN(start, PAGE_SIZE); > + end = _ALIGN_UP(end, PAGE_SIZE); > + > if (start < end) > printk ("Freeing initrd memory: %ldk freed\n", (end - start) >> 10); But here you test the aligned values. And they are aligned with opposite bias. Which means that if start == end (or is less than, but within the same page), a page that wasn't reserved (same 32 and 64 bit) gets freed. I thought "what happens if we are within a page of end, could we free the last page of bss?", but then I checked vmlinux.lds and we align end to page size. I thought other allocations should be safe, but then remembered: The flattened device tree (of which we continue to use the string table after boot) could be a problem. milton
next prev parent reply other threads:[~2011-05-22 21:17 UTC|newest] Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-05-20 21:26 [PATCH]powerpc: Force page alignment for early reserved memory Dave Carroll 2011-05-20 21:26 ` Dave Carroll 2011-05-20 22:27 ` Benjamin Herrenschmidt 2011-05-20 22:27 ` Benjamin Herrenschmidt 2011-05-20 23:23 ` [PATCH v2]powerpc: Force page alignment for initrd Dave Carroll 2011-05-20 23:23 ` Dave Carroll 2011-05-21 10:36 ` [v2] powerpc: " Milton Miller 2011-05-21 10:36 ` Milton Miller 2011-05-21 17:05 ` [PATCH v3] powerpc: Force page alignment for initrd reserved memory Dave Carroll 2011-05-21 17:05 ` Dave Carroll 2011-05-22 21:17 ` 'Milton Miller' [this message] 2011-05-22 21:17 ` [PATCH v3] powerpc: Force page alignment for initrd reserved memory, " 'Milton Miller' 2011-05-23 1:29 ` Dave Carroll 2011-05-23 1:29 ` Dave Carroll 2011-05-23 2:31 ` [PATCH v4] " Dave Carroll 2011-05-23 2:31 ` Dave Carroll 2011-05-23 16:50 ` [ " Dave Carroll 2011-05-23 16:50 ` Dave Carroll 2011-05-23 17:39 ` Milton Miller 2011-05-23 17:39 ` Milton Miller 2011-05-23 22:54 ` [PATCH v5] " Dave Carroll 2011-05-23 22:54 ` Dave Carroll 2011-05-25 9:28 ` [v5] " Milton Miller 2011-05-25 9:28 ` Milton Miller 2011-05-26 2:00 ` [PATCH v6] " Dave Carroll 2011-05-26 2:00 ` Dave Carroll 2011-05-26 2:32 ` [PATCH v7] " Dave Carroll 2011-05-26 2:32 ` Dave Carroll 2011-05-26 11:18 ` Milton Miller 2011-05-26 11:18 ` Milton Miller 2011-05-26 16:53 ` [PATCH v8] " Dave Carroll 2011-05-26 16:53 ` Dave Carroll 2011-06-11 1:38 ` [PATCH 1/2] powerpc: Move free_initmem to common code Dave Carroll 2011-06-11 1:38 ` Dave Carroll 2011-06-11 1:38 ` [PATCH 2/2] powerpc: Add printk companion for ppc_md.progress Dave Carroll 2011-06-11 1:38 ` Dave Carroll
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