[meta-intel] [PATCH] linux-intel: Backport patch to fix build with gcc7
Khem Raj
raj.khem at gmail.com
Mon Apr 17 16:40:38 PDT 2017
Signed-off-by: Khem Raj <raj.khem at gmail.com>
---
...ve-up-on-gcc-ilog2-constant-optimizations.patch | 127 +++++++++++++++++++++
common/recipes-kernel/linux/linux-intel_4.9.bb | 5 +-
2 files changed, 130 insertions(+), 2 deletions(-)
create mode 100644 common/recipes-kernel/linux/files/0001-give-up-on-gcc-ilog2-constant-optimizations.patch
diff --git a/common/recipes-kernel/linux/files/0001-give-up-on-gcc-ilog2-constant-optimizations.patch b/common/recipes-kernel/linux/files/0001-give-up-on-gcc-ilog2-constant-optimizations.patch
new file mode 100644
index 0000000..481e1b6
--- /dev/null
+++ b/common/recipes-kernel/linux/files/0001-give-up-on-gcc-ilog2-constant-optimizations.patch
@@ -0,0 +1,127 @@
+From c2812ad30bf55b62a5aefd3b1602a9c5d7f2dccc Mon Sep 17 00:00:00 2001
+From: Linus Torvalds <torvalds at linux-foundation.org>
+Date: Thu, 2 Mar 2017 12:17:22 -0800
+Subject: [PATCH] give up on gcc ilog2() constant optimizations
+
+gcc-7 has an "optimization" pass that completely screws up, and
+generates the code expansion for the (impossible) case of calling
+ilog2() with a zero constant, even when the code gcc compiles does not
+actually have a zero constant.
+
+And we try to generate a compile-time error for anybody doing ilog2() on
+a constant where that doesn't make sense (be it zero or negative). So
+now gcc7 will fail the build due to our sanity checking, because it
+created that constant-zero case that didn't actually exist in the source
+code.
+
+There's a whole long discussion on the kernel mailing about how to work
+around this gcc bug. The gcc people themselevs have discussed their
+"feature" in
+
+ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72785
+
+but it's all water under the bridge, because while it looked at one
+point like it would be solved by the time gcc7 was released, that was
+not to be.
+
+So now we have to deal with this compiler braindamage.
+
+And the only simple approach seems to be to just delete the code that
+tries to warn about bad uses of ilog2().
+
+So now "ilog2()" will just return 0 not just for the value 1, but for
+any non-positive value too.
+
+It's not like I can recall anybody having ever actually tried to use
+this function on any invalid value, but maybe the sanity check just
+meant that such code never made it out in public.
+
+Reported-by: Laura Abbott <labbott at redhat.com>
+Cc: John Stultz <john.stultz at linaro.org>,
+Cc: Thomas Gleixner <tglx at linutronix.de>
+Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
+Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
+---
+ include/linux/log2.h | 13 ++-----------
+ tools/include/linux/log2.h | 13 ++-----------
+ 2 files changed, 4 insertions(+), 22 deletions(-)
+
+diff --git a/include/linux/log2.h b/include/linux/log2.h
+index fd7ff3d..f38fae2 100644
+--- a/include/linux/log2.h
++++ b/include/linux/log2.h
+@@ -16,12 +16,6 @@
+ #include <linux/bitops.h>
+
+ /*
+- * deal with unrepresentable constant logarithms
+- */
+-extern __attribute__((const, noreturn))
+-int ____ilog2_NaN(void);
+-
+-/*
+ * non-constant log of base 2 calculators
+ * - the arch may override these in asm/bitops.h if they can be implemented
+ * more efficiently than using fls() and fls64()
+@@ -85,7 +79,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
+ #define ilog2(n) \
+ ( \
+ __builtin_constant_p(n) ? ( \
+- (n) < 1 ? ____ilog2_NaN() : \
++ (n) < 2 ? 0 : \
+ (n) & (1ULL << 63) ? 63 : \
+ (n) & (1ULL << 62) ? 62 : \
+ (n) & (1ULL << 61) ? 61 : \
+@@ -148,10 +142,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
+ (n) & (1ULL << 4) ? 4 : \
+ (n) & (1ULL << 3) ? 3 : \
+ (n) & (1ULL << 2) ? 2 : \
+- (n) & (1ULL << 1) ? 1 : \
+- (n) & (1ULL << 0) ? 0 : \
+- ____ilog2_NaN() \
+- ) : \
++ 1 ) : \
+ (sizeof(n) <= 4) ? \
+ __ilog2_u32(n) : \
+ __ilog2_u64(n) \
+diff --git a/tools/include/linux/log2.h b/tools/include/linux/log2.h
+index 4144666..d5677d3 100644
+--- a/tools/include/linux/log2.h
++++ b/tools/include/linux/log2.h
+@@ -13,12 +13,6 @@
+ #define _TOOLS_LINUX_LOG2_H
+
+ /*
+- * deal with unrepresentable constant logarithms
+- */
+-extern __attribute__((const, noreturn))
+-int ____ilog2_NaN(void);
+-
+-/*
+ * non-constant log of base 2 calculators
+ * - the arch may override these in asm/bitops.h if they can be implemented
+ * more efficiently than using fls() and fls64()
+@@ -78,7 +72,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
+ #define ilog2(n) \
+ ( \
+ __builtin_constant_p(n) ? ( \
+- (n) < 1 ? ____ilog2_NaN() : \
++ (n) < 2 ? 0 : \
+ (n) & (1ULL << 63) ? 63 : \
+ (n) & (1ULL << 62) ? 62 : \
+ (n) & (1ULL << 61) ? 61 : \
+@@ -141,10 +135,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
+ (n) & (1ULL << 4) ? 4 : \
+ (n) & (1ULL << 3) ? 3 : \
+ (n) & (1ULL << 2) ? 2 : \
+- (n) & (1ULL << 1) ? 1 : \
+- (n) & (1ULL << 0) ? 0 : \
+- ____ilog2_NaN() \
+- ) : \
++ 1 ) : \
+ (sizeof(n) <= 4) ? \
+ __ilog2_u32(n) : \
+ __ilog2_u64(n) \
+--
+1.9.1
+
diff --git a/common/recipes-kernel/linux/linux-intel_4.9.bb b/common/recipes-kernel/linux/linux-intel_4.9.bb
index 46821a9..d26a6ad 100644
--- a/common/recipes-kernel/linux/linux-intel_4.9.bb
+++ b/common/recipes-kernel/linux/linux-intel_4.9.bb
@@ -6,8 +6,9 @@ SRCREV_machine ?= "6f425e57c6afaed5d61cd9b8abe898bae97f9374"
SRCREV_meta ?= "b65e9b6153237e3ee898a01bc418c12f7404a681"
SRC_URI = "git://github.com/01org/linux-intel-4.9.git;protocol=https;name=machine;branch=${KBRANCH}; \
- git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-4.9;destsuffix=${KMETA}"
-
+ git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-4.9;destsuffix=${KMETA} \
+ file://0001-give-up-on-gcc-ilog2-constant-optimizations.patch \
+"
LINUX_VERSION ?= "4.9.15"
PV = "${LINUX_VERSION}+git${SRCPV}"
--
1.9.1
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