* linux-next: build failure while building Linus' tree
@ 2021-09-09 8:25 Stephen Rothwell
2021-09-09 22:50 ` Nick Desaulniers
0 siblings, 1 reply; 11+ messages in thread
From: Stephen Rothwell @ 2021-09-09 8:25 UTC (permalink / raw)
To: Baokun Li
Cc: Jens Axboe, Josef Bacik, Linux Kernel Mailing List,
Linux Next Mailing List
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Hi all,
Building Linus' tree, today's linux-next build (powerpc
ppc6xx_defconfig gcc4.9) failed like this:
ERROR: modpost: "__divdi3" [drivers/block/nbd.ko] undefined!
Caused by commit
fad7cd3310db ("nbd: add the check to prevent overflow in __nbd_ioctl()")
The added check_mul_overflow() call is being passed 64 bit values.
COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW is not set for this build (see
include/linux/overflow.h).
--
Cheers,
Stephen Rothwell
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^ permalink raw reply [flat|nested] 11+ messages in thread* Re: linux-next: build failure while building Linus' tree 2021-09-09 8:25 linux-next: build failure while building Linus' tree Stephen Rothwell @ 2021-09-09 22:50 ` Nick Desaulniers 0 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-09 22:50 UTC (permalink / raw) To: sfr Cc: axboe, josef, libaokun1, linux-kernel, linux-next, Rasmus Villemoes, llvm + Rasmus This was introduced in commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add fallback code") which added division using the `/` operator, which is problematic when checking for overflows of 64b operands on 32b targets. We'll probably need helpers from linux/math64.h and some combination of __builtin_choose_expr/__builtin_types_compatible_p. That will help us fix another compiler bug for older clang releases, too. https://github.com/ClangBuiltLinux/linux/issues/1438. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree @ 2021-09-09 22:50 ` Nick Desaulniers 0 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-09 22:50 UTC (permalink / raw) To: sfr Cc: axboe, josef, libaokun1, linux-kernel, linux-next, Rasmus Villemoes, llvm + Rasmus This was introduced in commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add fallback code") which added division using the `/` operator, which is problematic when checking for overflows of 64b operands on 32b targets. We'll probably need helpers from linux/math64.h and some combination of __builtin_choose_expr/__builtin_types_compatible_p. That will help us fix another compiler bug for older clang releases, too. https://github.com/ClangBuiltLinux/linux/issues/1438. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree 2021-09-09 22:50 ` Nick Desaulniers @ 2021-09-10 22:02 ` Nick Desaulniers -1 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:02 UTC (permalink / raw) To: sfr Cc: axboe, josef, libaokun1, linux-kernel, linux-next, Rasmus Villemoes, llvm, Arnd Bergmann, Nathan Chancellor On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > + Rasmus > > This was introduced in > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > fallback code") > which added division using the `/` operator, which is problematic when checking > for overflows of 64b operands on 32b targets. > > We'll probably need helpers from linux/math64.h and some combination of > __builtin_choose_expr/__builtin_types_compatible_p. > > That will help us fix another compiler bug for older clang releases, too. > https://github.com/ClangBuiltLinux/linux/issues/1438. Ok, I have something hacked up that I think will work: https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 This incomplete diff is a little hacked up to reproduce the issue with a known-bad revision of clang that demonstrates a similar issue to GCC 4.9. You can ignore the movement of check_mul_overflow and friends in include/linux/overflow.h. I think I'm going to break that up into 2 or 3 patches: 1. move is_signed_type from include/linux/overflow.h to perhaps include/linux/typecheck.h. 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use them in include/linux/overflow.h to fix GCC 4.9 3. move multiply fallbacks out of COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree @ 2021-09-10 22:02 ` Nick Desaulniers 0 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:02 UTC (permalink / raw) To: sfr Cc: axboe, josef, libaokun1, linux-kernel, linux-next, Rasmus Villemoes, llvm, Arnd Bergmann, Nathan Chancellor On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > + Rasmus > > This was introduced in > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > fallback code") > which added division using the `/` operator, which is problematic when checking > for overflows of 64b operands on 32b targets. > > We'll probably need helpers from linux/math64.h and some combination of > __builtin_choose_expr/__builtin_types_compatible_p. > > That will help us fix another compiler bug for older clang releases, too. > https://github.com/ClangBuiltLinux/linux/issues/1438. Ok, I have something hacked up that I think will work: https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 This incomplete diff is a little hacked up to reproduce the issue with a known-bad revision of clang that demonstrates a similar issue to GCC 4.9. You can ignore the movement of check_mul_overflow and friends in include/linux/overflow.h. I think I'm going to break that up into 2 or 3 patches: 1. move is_signed_type from include/linux/overflow.h to perhaps include/linux/typecheck.h. 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use them in include/linux/overflow.h to fix GCC 4.9 3. move multiply fallbacks out of COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree 2021-09-10 22:02 ` Nick Desaulniers @ 2021-09-10 22:17 ` Nick Desaulniers -1 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:17 UTC (permalink / raw) To: Rasmus Villemoes Cc: axboe, josef, libaokun1, linux-kernel, linux-next, llvm, Arnd Bergmann, Nathan Chancellor, sfr On Fri, Sep 10, 2021 at 3:02 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > > > + Rasmus > > > > This was introduced in > > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > > fallback code") > > which added division using the `/` operator, which is problematic when checking > > for overflows of 64b operands on 32b targets. > > > > We'll probably need helpers from linux/math64.h and some combination of > > __builtin_choose_expr/__builtin_types_compatible_p. > > > > That will help us fix another compiler bug for older clang releases, too. > > https://github.com/ClangBuiltLinux/linux/issues/1438. > > Ok, I have something hacked up that I think will work: > https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 hmm...playing around with adding some static asserts to the above, I don't think it's quite right, specifically: #define div_64(dividend, divisor) ({ \ typeof(dividend) z; might declare z with the expected sign, but not necessarily the correct width when the dividend is 32b but the divisor is 64b. Feels a bit like trying to encode the C type promotion rules in a macro... > This incomplete diff is a little hacked up to reproduce the issue with > a known-bad revision of clang that demonstrates a similar issue to GCC > 4.9. You can ignore the movement of check_mul_overflow and friends in > include/linux/overflow.h. > > I think I'm going to break that up into 2 or 3 patches: > 1. move is_signed_type from include/linux/overflow.h to perhaps > include/linux/typecheck.h. > 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use > them in include/linux/overflow.h to fix GCC 4.9 > 3. move multiply fallbacks out of > COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree @ 2021-09-10 22:17 ` Nick Desaulniers 0 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:17 UTC (permalink / raw) To: Rasmus Villemoes Cc: axboe, josef, libaokun1, linux-kernel, linux-next, llvm, Arnd Bergmann, Nathan Chancellor, sfr On Fri, Sep 10, 2021 at 3:02 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > > > + Rasmus > > > > This was introduced in > > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > > fallback code") > > which added division using the `/` operator, which is problematic when checking > > for overflows of 64b operands on 32b targets. > > > > We'll probably need helpers from linux/math64.h and some combination of > > __builtin_choose_expr/__builtin_types_compatible_p. > > > > That will help us fix another compiler bug for older clang releases, too. > > https://github.com/ClangBuiltLinux/linux/issues/1438. > > Ok, I have something hacked up that I think will work: > https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 hmm...playing around with adding some static asserts to the above, I don't think it's quite right, specifically: #define div_64(dividend, divisor) ({ \ typeof(dividend) z; might declare z with the expected sign, but not necessarily the correct width when the dividend is 32b but the divisor is 64b. Feels a bit like trying to encode the C type promotion rules in a macro... > This incomplete diff is a little hacked up to reproduce the issue with > a known-bad revision of clang that demonstrates a similar issue to GCC > 4.9. You can ignore the movement of check_mul_overflow and friends in > include/linux/overflow.h. > > I think I'm going to break that up into 2 or 3 patches: > 1. move is_signed_type from include/linux/overflow.h to perhaps > include/linux/typecheck.h. > 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use > them in include/linux/overflow.h to fix GCC 4.9 > 3. move multiply fallbacks out of > COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree 2021-09-10 22:17 ` Nick Desaulniers @ 2021-09-10 22:26 ` Nick Desaulniers -1 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:26 UTC (permalink / raw) To: Rasmus Villemoes Cc: axboe, josef, libaokun1, linux-kernel, linux-next, llvm, Arnd Bergmann, Nathan Chancellor, sfr On Fri, Sep 10, 2021 at 3:17 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Fri, Sep 10, 2021 at 3:02 PM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > > > > > + Rasmus > > > > > > This was introduced in > > > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > > > fallback code") > > > which added division using the `/` operator, which is problematic when checking > > > for overflows of 64b operands on 32b targets. > > > > > > We'll probably need helpers from linux/math64.h and some combination of > > > __builtin_choose_expr/__builtin_types_compatible_p. > > > > > > That will help us fix another compiler bug for older clang releases, too. > > > https://github.com/ClangBuiltLinux/linux/issues/1438. > > > > Ok, I have something hacked up that I think will work: > > https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 > > hmm...playing around with adding some static asserts to the above, I ah! static_assert can't be used for the type agnostic macros, BUILD_BUG_ON needs to be used in its place. Ok, let me add a few and see if that can help instill some confidence here. > don't think it's quite right, specifically: > #define div_64(dividend, divisor) ({ \ > typeof(dividend) z; > > might declare z with the expected sign, but not necessarily the > correct width when the dividend is 32b but the divisor is 64b. Feels > a bit like trying to encode the C type promotion rules in a macro... > > > This incomplete diff is a little hacked up to reproduce the issue with > > a known-bad revision of clang that demonstrates a similar issue to GCC > > 4.9. You can ignore the movement of check_mul_overflow and friends in > > include/linux/overflow.h. > > > > I think I'm going to break that up into 2 or 3 patches: > > 1. move is_signed_type from include/linux/overflow.h to perhaps > > include/linux/typecheck.h. > > 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use > > them in include/linux/overflow.h to fix GCC 4.9 > > 3. move multiply fallbacks out of > > COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. > > -- > > Thanks, > > ~Nick Desaulniers > > > > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree @ 2021-09-10 22:26 ` Nick Desaulniers 0 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:26 UTC (permalink / raw) To: Rasmus Villemoes Cc: axboe, josef, libaokun1, linux-kernel, linux-next, llvm, Arnd Bergmann, Nathan Chancellor, sfr On Fri, Sep 10, 2021 at 3:17 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Fri, Sep 10, 2021 at 3:02 PM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > > > > > + Rasmus > > > > > > This was introduced in > > > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > > > fallback code") > > > which added division using the `/` operator, which is problematic when checking > > > for overflows of 64b operands on 32b targets. > > > > > > We'll probably need helpers from linux/math64.h and some combination of > > > __builtin_choose_expr/__builtin_types_compatible_p. > > > > > > That will help us fix another compiler bug for older clang releases, too. > > > https://github.com/ClangBuiltLinux/linux/issues/1438. > > > > Ok, I have something hacked up that I think will work: > > https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 > > hmm...playing around with adding some static asserts to the above, I ah! static_assert can't be used for the type agnostic macros, BUILD_BUG_ON needs to be used in its place. Ok, let me add a few and see if that can help instill some confidence here. > don't think it's quite right, specifically: > #define div_64(dividend, divisor) ({ \ > typeof(dividend) z; > > might declare z with the expected sign, but not necessarily the > correct width when the dividend is 32b but the divisor is 64b. Feels > a bit like trying to encode the C type promotion rules in a macro... > > > This incomplete diff is a little hacked up to reproduce the issue with > > a known-bad revision of clang that demonstrates a similar issue to GCC > > 4.9. You can ignore the movement of check_mul_overflow and friends in > > include/linux/overflow.h. > > > > I think I'm going to break that up into 2 or 3 patches: > > 1. move is_signed_type from include/linux/overflow.h to perhaps > > include/linux/typecheck.h. > > 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use > > them in include/linux/overflow.h to fix GCC 4.9 > > 3. move multiply fallbacks out of > > COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. > > -- > > Thanks, > > ~Nick Desaulniers > > > > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree 2021-09-10 22:26 ` Nick Desaulniers @ 2021-09-10 22:34 ` Nick Desaulniers -1 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:34 UTC (permalink / raw) To: Rasmus Villemoes Cc: axboe, josef, libaokun1, linux-kernel, linux-next, llvm, Arnd Bergmann, Nathan Chancellor, sfr On Fri, Sep 10, 2021 at 3:26 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Fri, Sep 10, 2021 at 3:17 PM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > On Fri, Sep 10, 2021 at 3:02 PM Nick Desaulniers > > <ndesaulniers@google.com> wrote: > > > > > > On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > > > > > > > + Rasmus > > > > > > > > This was introduced in > > > > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > > > > fallback code") > > > > which added division using the `/` operator, which is problematic when checking > > > > for overflows of 64b operands on 32b targets. > > > > > > > > We'll probably need helpers from linux/math64.h and some combination of > > > > __builtin_choose_expr/__builtin_types_compatible_p. > > > > > > > > That will help us fix another compiler bug for older clang releases, too. > > > > https://github.com/ClangBuiltLinux/linux/issues/1438. > > > > > > Ok, I have something hacked up that I think will work: > > > https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 > > > > hmm...playing around with adding some static asserts to the above, I > > ah! static_assert can't be used for the type agnostic macros, > BUILD_BUG_ON needs to be used in its place. Ok, let me add a few and > see if that can help instill some confidence here. Ah, I just saw your comment now about raising the minimum required version of gcc to 5.1. https://github.com/ClangBuiltLinux/linux/issues/1438#issuecomment-916745801 > > > This incomplete diff is a little hacked up to reproduce the issue with > > > a known-bad revision of clang that demonstrates a similar issue to GCC > > > 4.9. You can ignore the movement of check_mul_overflow and friends in > > > include/linux/overflow.h. > > > > > > I think I'm going to break that up into 2 or 3 patches: > > > 1. move is_signed_type from include/linux/overflow.h to perhaps > > > include/linux/typecheck.h. > > > 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use > > > them in include/linux/overflow.h to fix GCC 4.9 > > > 3. move multiply fallbacks out of > > > COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. In that case, I do have __mulodi4() rewritten from compiler-rt to be usable in the kernel. -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: linux-next: build failure while building Linus' tree @ 2021-09-10 22:34 ` Nick Desaulniers 0 siblings, 0 replies; 11+ messages in thread From: Nick Desaulniers @ 2021-09-10 22:34 UTC (permalink / raw) To: Rasmus Villemoes Cc: axboe, josef, libaokun1, linux-kernel, linux-next, llvm, Arnd Bergmann, Nathan Chancellor, sfr On Fri, Sep 10, 2021 at 3:26 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Fri, Sep 10, 2021 at 3:17 PM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > On Fri, Sep 10, 2021 at 3:02 PM Nick Desaulniers > > <ndesaulniers@google.com> wrote: > > > > > > On Thu, Sep 9, 2021 at 3:50 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > > > > > > > + Rasmus > > > > > > > > This was introduced in > > > > commit f0907827a8a91 ("compiler.h: enable builtin overflow checkers and add > > > > fallback code") > > > > which added division using the `/` operator, which is problematic when checking > > > > for overflows of 64b operands on 32b targets. > > > > > > > > We'll probably need helpers from linux/math64.h and some combination of > > > > __builtin_choose_expr/__builtin_types_compatible_p. > > > > > > > > That will help us fix another compiler bug for older clang releases, too. > > > > https://github.com/ClangBuiltLinux/linux/issues/1438. > > > > > > Ok, I have something hacked up that I think will work: > > > https://gist.github.com/nickdesaulniers/2479818f4983bbf2d688cebbab435863 > > > > hmm...playing around with adding some static asserts to the above, I > > ah! static_assert can't be used for the type agnostic macros, > BUILD_BUG_ON needs to be used in its place. Ok, let me add a few and > see if that can help instill some confidence here. Ah, I just saw your comment now about raising the minimum required version of gcc to 5.1. https://github.com/ClangBuiltLinux/linux/issues/1438#issuecomment-916745801 > > > This incomplete diff is a little hacked up to reproduce the issue with > > > a known-bad revision of clang that demonstrates a similar issue to GCC > > > 4.9. You can ignore the movement of check_mul_overflow and friends in > > > include/linux/overflow.h. > > > > > > I think I'm going to break that up into 2 or 3 patches: > > > 1. move is_signed_type from include/linux/overflow.h to perhaps > > > include/linux/typecheck.h. > > > 2. add div64_x64, div_x64, and div_64 to include/linux/math64.h, use > > > them in include/linux/overflow.h to fix GCC 4.9 > > > 3. move multiply fallbacks out of > > > COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for clang < 14. In that case, I do have __mulodi4() rewritten from compiler-rt to be usable in the kernel. -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2021-09-10 22:35 UTC | newest] Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-09-09 8:25 linux-next: build failure while building Linus' tree Stephen Rothwell 2021-09-09 22:50 ` Nick Desaulniers 2021-09-09 22:50 ` Nick Desaulniers 2021-09-10 22:02 ` Nick Desaulniers 2021-09-10 22:02 ` Nick Desaulniers 2021-09-10 22:17 ` Nick Desaulniers 2021-09-10 22:17 ` Nick Desaulniers 2021-09-10 22:26 ` Nick Desaulniers 2021-09-10 22:26 ` Nick Desaulniers 2021-09-10 22:34 ` Nick Desaulniers 2021-09-10 22:34 ` Nick Desaulniers
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