Messages in this thread | | | Subject | Re: [PATCH v3] powerpc: Force page alignment for initrd reserved memory | From | 'Milton Miller' <> | Subject | Re: [PATCH v3] powerpc: Force page alignment for initrd reserved memory | Date | Sun, 22 May 2011 16:17:18 -0500 |
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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
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