Re: [PATCH v3] powerpc: Force page alignment for initrd reserved memory
From: 'Milton Miller' <hidden>
Date: 2011-05-22 21:17:30
Also in:
lkml
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
quoted hunk ↗ jump to hunk
Signed-off-by: Dave Carroll <redacted> --- 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