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Date: Wed, 18 Jun 2014 13:45:34 -0700 From: "Luis R. Rodriguez" <mcgrof@...not-panic.com> To: gregkh@...uxfoundation.org, akpm@...ux-foundation.org, hpa@...ux.intel.com Cc: linux-kernel@...r.kernel.org, "Luis R. Rodriguez" <mcgrof@...e.com>, Andrew Lunn <andrew@...n.ch>, Stephen Warren <swarren@...dotorg.org>, Michal Hocko <mhocko@...e.cz>, Petr Mladek <pmladek@...e.cz>, Joe Perches <joe@...ches.com>, Arun KS <arunks.linux@...il.com>, Kees Cook <keescook@...omium.org>, Davidlohr Bueso <davidlohr@...com>, Chris Metcalf <cmetcalf@...era.com> Subject: [PATCH v8 1/4] printk: make dynamic kernel ring buffer alignment explicit From: "Luis R. Rodriguez" <mcgrof@...e.com> 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 by Andrew 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. Cc: Andrew Lunn <andrew@...n.ch> Cc: Stephen Warren <swarren@...dotorg.org> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: Michal Hocko <mhocko@...e.cz> Cc: Petr Mladek <pmladek@...e.cz> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Joe Perches <joe@...ches.com> Cc: Arun KS <arunks.linux@...il.com> Cc: Kees Cook <keescook@...omium.org> Cc: Davidlohr Bueso <davidlohr@...com> Cc: Chris Metcalf <cmetcalf@...era.com> Cc: linux-kernel@...r.kernel.org Acked-by: Petr Mladek <pmladek@...e.cz> Tested-by: Petr Mladek <pmladek@...e.cz> Signed-off-by: Luis R. Rodriguez <mcgrof@...e.com> --- kernel/printk/printk.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ea2d5f6..78ceccf 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -853,9 +853,10 @@ void __init setup_log_buf(int early) if (early) { new_log_buf = - memblock_virt_alloc(new_log_buf_len, PAGE_SIZE); + memblock_virt_alloc(new_log_buf_len, LOG_ALIGN); } else { - new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 0); + new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, + LOG_ALIGN); } if (unlikely(!new_log_buf)) { -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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