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Groups > linux.kernel > #1633348
| From | "H. Peter Anvin" <hpa@zytor.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication |
| Date | 2017-04-29 23:40 +0200 |
| Message-ID | <tBIfT-2Xk-1@gated-at.bofh.it> (permalink) |
| References | <tACcx-7k3-3@gated-at.bofh.it> <tACme-7Du-27@gated-at.bofh.it> <tACFz-7Oy-5@gated-at.bofh.it> <tACFz-7Oy-7@gated-at.bofh.it> <tACFz-7Oy-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 04/26/17 14:29, Greg Hackmann wrote: > On 04/26/2017 02:24 PM, hpa@zytor.com wrote: >>>> This really feels like a "fix your compiler" issue. >>> >>> We already use the other forms, what's so bad about adding mul too? >>> And if this lets us build under clang, all the better. >>> >>> -Kees >> >> It's not bad per se, but if this doesn't eventually gets fixed in >> clang we'll have no end of this crap. >> > > AIUI the "problem" is that clang is spilling mix_const into memory > rather than assigning it to a register. This is perfectly legal since > mix_const has a constraint of "rm". But mul needs a suffix when the > input is a memory location, since it can't infer the multiplication > width from the input operand anymore. > > You get the same error message with gcc if you force it to use a memory > location, by narrowing the constraint from "rm" to "m". OK, that's a genuine bug. Please explain that in the comment; it has nothing to do with clang. -hpa
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[PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication Matthias Kaehlcke <mka@chromium.org> - 2017-04-26 23:00 +0200
Re: [PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication hpa@zytor.com - 2017-04-26 23:10 +0200
Re: [PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication Greg Hackmann <ghackmann@google.com> - 2017-04-26 23:30 +0200
Re: [PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication "H. Peter Anvin" <hpa@zytor.com> - 2017-04-29 23:40 +0200
Re: [PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication Kees Cook <keescook@chromium.org> - 2017-04-26 23:30 +0200
Re: [PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication hpa@zytor.com - 2017-04-26 23:40 +0200
Re: [PATCH v2] x86/mm/kaslr: Use _ASM_MUL macro for multiplication Kees Cook <keescook@chromium.org> - 2017-04-27 00:10 +0200
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