SliTaz Repositories

     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/linux/stuff/linux-fix-noreturn-attributes-gcc8.patch	Tue Apr 16 19:01:01 2024 +0000
     1.3 @@ -0,0 +1,77 @@
     1.4 +gcc-7 has an "optimization" pass that completely screws up, and
     1.5 +generates the code expansion for the (impossible) case of calling
     1.6 +ilog2() with a zero constant, even when the code gcc compiles does not
     1.7 +actually have a zero constant.
     1.8 +
     1.9 +And we try to generate a compile-time error for anybody doing ilog2() on
    1.10 +a constant where that doesn't make sense (be it zero or negative).  So
    1.11 +now gcc7 will fail the build due to our sanity checking, because it
    1.12 +created that constant-zero case that didn't actually exist in the source
    1.13 +code.
    1.14 +
    1.15 +There's a whole long discussion on the kernel mailing about how to work
    1.16 +around this gcc bug.  The gcc people themselevs have discussed their
    1.17 +"feature" in
    1.18 +
    1.19 +   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72785
    1.20 +
    1.21 +but it's all water under the bridge, because while it looked at one
    1.22 +point like it would be solved by the time gcc7 was released, that was
    1.23 +not to be.
    1.24 +
    1.25 +So now we have to deal with this compiler braindamage.
    1.26 +
    1.27 +And the only simple approach seems to be to just delete the code that
    1.28 +tries to warn about bad uses of ilog2().
    1.29 +
    1.30 +So now "ilog2()" will just return 0 not just for the value 1, but for
    1.31 +any non-positive value too.
    1.32 +
    1.33 +It's not like I can recall anybody having ever actually tried to use
    1.34 +this function on any invalid value, but maybe the sanity check just
    1.35 +meant that such code never made it out in public.
    1.36 +
    1.37 +Reported-by: Laura Abbott <labbott@redhat.com>
    1.38 +Cc: John Stultz <john.stultz@linaro.org>,
    1.39 +Cc: Thomas Gleixner <tglx@linutronix.de>
    1.40 +Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    1.41 +Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    1.42 +
    1.43 +diff --git a/include/linux/log2.h b/include/linux/log2.h
    1.44 +index ef3d4f67118ce..c373295f359fa 100644
    1.45 +--- a/include/linux/log2.h
    1.46 ++++ b/include/linux/log2.h
    1.47 +@@ -16,12 +16,6 @@
    1.48 + #include <linux/bitops.h>
    1.49 + 
    1.50 + /*
    1.51 +- * deal with unrepresentable constant logarithms
    1.52 +- */
    1.53 +-extern __attribute__((const, noreturn))
    1.54 +-int ____ilog2_NaN(void);
    1.55 +-
    1.56 +-/*
    1.57 +  * non-constant log of base 2 calculators
    1.58 +  * - the arch may override these in asm/bitops.h if they can be implemented
    1.59 +  *   more efficiently than using fls() and fls64()
    1.60 +@@ -85,7 +79,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
    1.61 + #define ilog2(n)				\
    1.62 + (						\
    1.63 + 	__builtin_constant_p(n) ? (		\
    1.64 +-		(n) < 1 ? ____ilog2_NaN() :	\
    1.65 ++		(n) < 2 ? 0 :			\
    1.66 + 		(n) & (1ULL << 63) ? 63 :	\
    1.67 + 		(n) & (1ULL << 62) ? 62 :	\
    1.68 + 		(n) & (1ULL << 61) ? 61 :	\
    1.69 +@@ -148,10 +142,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
    1.70 + 		(n) & (1ULL <<  4) ?  4 :	\
    1.71 + 		(n) & (1ULL <<  3) ?  3 :	\
    1.72 + 		(n) & (1ULL <<  2) ?  2 :	\
    1.73 +-		(n) & (1ULL <<  1) ?  1 :	\
    1.74 +-		(n) & (1ULL <<  0) ?  0 :	\
    1.75 +-		____ilog2_NaN()			\
    1.76 +-				   ) :		\
    1.77 ++		1 ) :				\
    1.78 + 	(sizeof(n) <= 4) ?			\
    1.79 + 	__ilog2_u32(n) :			\
    1.80 + 	__ilog2_u64(n)				\