[OE-core] [PATCH 7/7] linux-yocto_4.1.bb: Fix build with gcc7
Bruce Ashfield
bruce.ashfield at gmail.com
Sat May 13 16:16:55 UTC 2017
On Sat, May 13, 2017 at 12:10 PM, Khem Raj <raj.khem at gmail.com> wrote:
> On Sat, May 13, 2017 at 8:45 AM, Bruce Ashfield
> <bruce.ashfield at gmail.com> wrote:
> > I already have this queued, I'm just not sending any kernel pull requests
> > while
> > the release is finalizing.
>
> its already done yesterday :) so you are free to send
>
oh! I hadn't noticed. I was heads down working on some features. I'll update
and send my queue tonight.
I attached the patch to show it exists :D
Cheers,
Bruce
>
> >
> > So please, do not queue or merge this change.
> >
>
> sure
>
> > Bruce
> >
> > On Fri, May 12, 2017 at 10:59 PM, Khem Raj <raj.khem at gmail.com> wrote:
> >>
> >> Signed-off-by: Khem Raj <raj.khem at gmail.com>
> >> ---
> >> ...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 <torvalds at linux-foundation.org>
> >> +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 <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>
> >> +Cc: Jiri Slaby <jslaby at suse.cz>
> >> +Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> >> +Signed-off-by: Khem Raj <raj.khem at gmail.com>
> >> +---
> >> +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
> >> Openembedded-core at lists.openembedded.org
> >> http://lists.openembedded.org/mailman/listinfo/openembedded-core
> >
> >
> >
> >
> > --
> > "Thou shalt not follow the NULL pointer, for chaos and madness await
> thee at
> > its end"
>
--
"Thou shalt not follow the NULL pointer, for chaos and madness await thee
at its end"
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