2013-04-29 22:39:10

by Jerry Hoemann

[permalink] [raw]
Subject: [PATCH] x86/mm: account for PGDIR_SIZE alignment

Patch for 3.0-stable. Function find_early_table_space removed upstream.

Fixes panic in alloc_low_page due to pgt_buf overflow during
init_memory_mapping.

find_early_table_space sizes pgt_buf based upon the size of the
memory being mapped, but it does not take into account the alignment
of the memory. When the region being mapped spans a 512GB (PGDIR_SIZE)
alignment, a panic from alloc_low_pages occurs.

kernel_physical_mapping_init takes into account PGDIR_SIZE alignment.
This causes an extra call to alloc_low_page to be made. This extra call
isn't accounted for by find_early_table_space and causes a kernel panic.

Change is to take into account PGDIR_SIZE alignment in find_early_table_space.

Signed-off-by: Jerry Hoemann <[email protected]>
---
arch/x86/mm/init.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index c22c423..96c4577 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -44,11 +44,15 @@ static void __init find_early_table_space(struct map_range *mr, int nr_range)
int i;
unsigned long puds = 0, pmds = 0, ptes = 0, tables;
unsigned long start = 0, good_end;
+ unsigned long pgd_extra = 0;
phys_addr_t base;

for (i = 0; i < nr_range; i++) {
unsigned long range, extra;

+ if ((mr[i].end >> PGDIR_SHIFT) - (mr[i].start >> PGDIR_SHIFT))
+ pgd_extra++;
+
range = mr[i].end - mr[i].start;
puds += (range + PUD_SIZE - 1) >> PUD_SHIFT;

@@ -73,6 +77,7 @@ static void __init find_early_table_space(struct map_range *mr, int nr_range)
tables = roundup(puds * sizeof(pud_t), PAGE_SIZE);
tables += roundup(pmds * sizeof(pmd_t), PAGE_SIZE);
tables += roundup(ptes * sizeof(pte_t), PAGE_SIZE);
+ tables += (pgd_extra * PAGE_SIZE);

#ifdef CONFIG_X86_32
/* for fixmap */
--
1.8.1.4


2013-04-29 22:47:25

by Greg KH

[permalink] [raw]
Subject: Re: [PATCH] x86/mm: account for PGDIR_SIZE alignment

On Mon, Apr 29, 2013 at 04:38:49PM -0600, Jerry Hoemann wrote:
> Patch for 3.0-stable. Function find_early_table_space removed upstream.

No other stable kernel needs it? Why not also cc:
[email protected] about this?

thanks,

greg k-h