Signed-off-by: Khem Raj <[email protected]> --- ...ve-up-on-gcc-ilog2-constant-optimizations.patch | 134 +++++++++++++++++++++ meta/recipes-kernel/linux/linux-yocto_4.1.bb | 2 + 2 files changed, 136 insertions(+) create mode 100644 meta/recipes-kernel/linux/linux-yocto/0001-give-up-on-gcc-ilog2-constant-optimizations.patch
diff --git a/meta/recipes-kernel/linux/linux-yocto/0001-give-up-on-gcc-ilog2-constant-optimizations.patch b/meta/recipes-kernel/linux/linux-yocto/0001-give-up-on-gcc-ilog2-constant-optimizations.patch new file mode 100644 index 0000000000..35c4484f20 --- /dev/null +++ b/meta/recipes-kernel/linux/linux-yocto/0001-give-up-on-gcc-ilog2-constant-optimizations.patch @@ -0,0 +1,134 @@ +From 273bf720b7acb5f808337fe57c5f400422a30051 Mon Sep 17 00:00:00 2001 +From: Linus Torvalds <[email protected]> +Date: Thu, 2 Mar 2017 12:17:22 -0800 +Subject: [PATCH] give up on gcc ilog2() constant optimizations + +commit 474c90156c8dcc2fa815e6716cc9394d7930cb9c upstream. + +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 <[email protected]> +Cc: John Stultz <[email protected]>, +Cc: Thomas Gleixner <[email protected]> +Cc: Ard Biesheuvel <[email protected]> +Signed-off-by: Linus Torvalds <[email protected]> +Cc: Jiri Slaby <[email protected]> +Signed-off-by: Greg Kroah-Hartman <[email protected]> +Signed-off-by: Khem Raj <[email protected]> +--- +Upstream-Status: Backport + + 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 fd7ff3d91e6a..f38fae23bdac 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 41446668ccce..d5677d39c1e4 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) \ +-- +2.12.2 + diff --git a/meta/recipes-kernel/linux/linux-yocto_4.1.bb b/meta/recipes-kernel/linux/linux-yocto_4.1.bb index bf7f266ee6..f90d5159d5 100644 --- a/meta/recipes-kernel/linux/linux-yocto_4.1.bb +++ b/meta/recipes-kernel/linux/linux-yocto_4.1.bb @@ -24,6 +24,8 @@ SRCREV_meta ?= "7140ddb86e4b01529185e6d4a606001ad152b8f3" SRC_URI = "git://git.yoctoproject.org/linux-yocto-4.1.git;name=machine;branch=${KBRANCH}; \ git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-4.1;destsuffix=${KMETA}" +SRC_URI += "file://0001-give-up-on-gcc-ilog2-constant-optimizations.patch" + LINUX_VERSION ?= "4.1.38" PV = "${LINUX_VERSION}+git${SRCPV}" -- 2.13.0 -- _______________________________________________ Openembedded-core mailing list [email protected] http://lists.openembedded.org/mailman/listinfo/openembedded-core
