From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Thu, 15 Jun 2017 09:45:54 +0000 (+0200)
Subject: 4.9-stable patches
X-Git-Tag: v4.9.33~17
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=bafafb5a7a7b723ce99695db9d664c6a31d4ee35;p=thirdparty%2Fkernel%2Fstable-queue.git

4.9-stable patches

added patches:
	log2-make-order_base_2-behave-correctly-on-const-input-value-zero.patch
---

diff --git a/queue-4.9/log2-make-order_base_2-behave-correctly-on-const-input-value-zero.patch b/queue-4.9/log2-make-order_base_2-behave-correctly-on-const-input-value-zero.patch
new file mode 100644
index 00000000000..238f0289dff
--- /dev/null
+++ b/queue-4.9/log2-make-order_base_2-behave-correctly-on-const-input-value-zero.patch
@@ -0,0 +1,59 @@
+From 29905b52fad0854351f57bab867647e4982285bf Mon Sep 17 00:00:00 2001
+From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
+Date: Thu, 2 Feb 2017 18:05:26 +0000
+Subject: log2: make order_base_2() behave correctly on const input value zero
+
+From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
+
+commit 29905b52fad0854351f57bab867647e4982285bf upstream.
+
+The function order_base_2() is defined (according to the comment block)
+as returning zero on input zero, but subsequently passes the input into
+roundup_pow_of_two(), which is explicitly undefined for input zero.
+
+This has gone unnoticed until now, but optimization passes in GCC 7 may
+produce constant folded function instances where a constant value of
+zero is passed into order_base_2(), resulting in link errors against the
+deliberately undefined '____ilog2_NaN'.
+
+So update order_base_2() to adhere to its own documented interface.
+
+[ See
+
+     http://marc.info/?l=linux-kernel&m=147672952517795&w=2
+
+  and follow-up discussion for more background. The gcc "optimization
+  pass" is really just broken, but now the GCC trunk problem seems to
+  have escaped out of just specially built daily images, so we need to
+  work around it in mainline.    - Linus ]
+
+Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ include/linux/log2.h |   13 ++++++++++++-
+ 1 file changed, 12 insertions(+), 1 deletion(-)
+
+--- a/include/linux/log2.h
++++ b/include/linux/log2.h
+@@ -194,6 +194,17 @@ unsigned long __rounddown_pow_of_two(uns
+  *  ... and so on.
+  */
+ 
+-#define order_base_2(n) ilog2(roundup_pow_of_two(n))
++static inline __attribute_const__
++int __order_base_2(unsigned long n)
++{
++	return n > 1 ? ilog2(n - 1) + 1 : 0;
++}
+ 
++#define order_base_2(n)				\
++(						\
++	__builtin_constant_p(n) ? (		\
++		((n) == 0 || (n) == 1) ? 0 :	\
++		ilog2((n) - 1) + 1) :		\
++	__order_base_2(n)			\
++)
+ #endif /* _LINUX_LOG2_H */
diff --git a/queue-4.9/series b/queue-4.9/series
index d15be1766a5..ba9658cd678 100644
--- a/queue-4.9/series
+++ b/queue-4.9/series
@@ -31,3 +31,4 @@ pm-runtime-avoid-false-positive-warnings-from-might_sleep_if.patch
 jump-label-pass-kbuild_cflags-when-checking-for-asm-goto-support.patch
 shmem-fix-sleeping-from-atomic-context.patch
 kasan-respect-proc-sys-kernel-traceoff_on_warning.patch
+log2-make-order_base_2-behave-correctly-on-const-input-value-zero.patch