Per-CPU allocations are not guaranteed to be physically contiguous.
However, kdump kernel and user-space code assumes that per-CPU
memory, used for saving CPU registers on crash, is.
This can cause corrupted /proc/vmcore in some cases - the main
symptom being huge ELF note section.
Force page alignment for note_buf_t to ensure that this assumption holds.
Signed-off-by: Eugene Surovegin <surovegin at google.com>
CC: Eric Biederman <ebiederm at xmission.com>
CC: Vivek Goyal <vgoyal at redhat.com>
CC: kexec-list <kexec at lists.infradead.org>
---
kernel/kexec.c | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 7b08867..e641b5c 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1232,8 +1232,13 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
static int __init crash_notes_memory_init(void)
{
- /* Allocate memory for saving cpu registers. */
- crash_notes = alloc_percpu(note_buf_t);
+ /* Allocate memory for saving cpu registers.
+ * Force page alignment to avoid crossing physical page boundary -
+ * kexec-tools and kernel /proc/vmcore handler assume these per-CPU
+ * chunks are physically contiguous.
+ */
+ crash_notes = (note_buf_t __percpu *)__alloc_percpu(sizeof(note_buf_t),
+ PAGE_SIZE);
if (!crash_notes) {
printk("Kexec: Memory allocation for saving cpu register"
" states failed\n");
--
1.7.9.1
