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authorLuis R. Rodriguez <mcgrof@suse.com>2014-08-06 19:08:49 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-08-06 21:01:23 -0400
commit7030017752437cebc3ec5590735bd89ead1e4cb8 (patch)
treeb62f3cd07c1e85a2de22e8e068771387c74b6562 /kernel
parent90a856436ddafbe0c6f8c18d7fc21aed3784e227 (diff)
printk: make dynamic kernel ring buffer alignment explicit
We have to consider alignment for the ring buffer both for the default static size, and then also for when an dynamic allocation is made when the log_buf_len=n kernel parameter is passed to set the size specifically to a size larger than the default size set by the architecture through CONFIG_LOG_BUF_SHIFT. The default static kernel ring buffer can be aligned properly if architectures set CONFIG_LOG_BUF_SHIFT properly, we provide ranges for the size though so even if CONFIG_LOG_BUF_SHIFT has a sensible aligned value it can be reduced to a non aligned value. Commit 6ebb017de9 ("printk: Fix alignment of buf causing crash on ARM EABI") by Andrew Lunn ensures the static buffer is always aligned and the decision of alignment is done by the compiler by using __alignof__(struct log). When log_buf_len=n is used we allocate the ring buffer dynamically. Dynamic allocation varies, for the early allocation called before setup_arch() memblock_virt_alloc() requests a page aligment and for the default kernel allocation memblock_virt_alloc_nopanic() requests no special alignment, which in turn ends up aligning the allocation to SMP_CACHE_BYTES, which is L1 cache aligned. Since we already have the required alignment for the kernel ring buffer though we can do better and request explicit alignment for LOG_ALIGN. This does that to be safe and make dynamic allocation alignment explicit. Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com> Tested-by: Petr Mladek <pmladek@suse.cz> Acked-by: Petr Mladek <pmladek@suse.cz> Cc: Andrew Lunn <andrew@lunn.ch> Cc: Stephen Warren <swarren@wwwdotorg.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Petr Mladek <pmladek@suse.cz> Cc: Joe Perches <joe@perches.com> Cc: Arun KS <arunks.linux@gmail.com> Cc: Kees Cook <keescook@chromium.org> Cc: Davidlohr Bueso <davidlohr@hp.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/printk/printk.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 13e839dbca07..6f598f92f2a1 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -853,9 +853,10 @@ void __init setup_log_buf(int early)
853 853
854 if (early) { 854 if (early) {
855 new_log_buf = 855 new_log_buf =
856 memblock_virt_alloc(new_log_buf_len, PAGE_SIZE); 856 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
857 } else { 857 } else {
858 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 0); 858 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
859 LOG_ALIGN);
859 } 860 }
860 861
861 if (unlikely(!new_log_buf)) { 862 if (unlikely(!new_log_buf)) {