Date: Fri, 29 Dec 2023 22:20:19 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Harry Schmalzbauer <freebsd@omnilan.de> Cc: Dimitry Andric <dim@freebsd.org>, FreeBSD-STABLE <freebsd-stable@freebsd.org> Subject: Re: SIGILL when CPUTYPE set to anyting witjh avx and CFLAGS -O2 Message-ID: <ZY8qA7SKywXh_Yac@kib.kiev.ua> In-Reply-To: <62cc8fed-6acd-45fb-a138-ac7cd218191a@omnilan.de> References: <accdf012-1b04-4227-9b0c-a78e94133fc2@omnilan.de> <72107B4B-F279-471B-8A8F-5B94C5EEDA47@FreeBSD.org> <62cc8fed-6acd-45fb-a138-ac7cd218191a@omnilan.de>
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On Fri, Dec 29, 2023 at 09:12:35PM +0100, Harry Schmalzbauer wrote:
> On 12/29/23 18:00, Dimitry Andric wrote:
> > On 29 Dec 2023, at 11:14, Harry Schmalzbauer <freebsd@omnilan.de> wrote:
> > >
> > > at least since 14-release, I can't compile base/ports with CPUTYPE post nehalem. Any '-march' declaring AVX(*) capability leads to SIGILLing binaries with default -O2 CFLAGS.
> ..
> > >
> > > If I compile without CFLAGS -O2 ("CFLAGS= -pipe"), -march=skylake-avx512 the binary doens't crash with SIGILL.
> > >
> > > Is CPUTYPE supposed to stay untouched these days?
> >
> > Obviously not, but are you sure your target CPU is correct? If it is not, the compiler may insert unsupported instructions.
>
> Ho Dimitry, thanks for your attention!
> I have to admit that I know much too less about contemporary compilers and
> CPUs likewise, but target CPU matches -march ;-)
> I nailed it down to AVX instructions. Starting with 'sandybridge', Intel
> CPUs provide avx instruction units, and starting with CPUTYPE?=sandybridge,
> binaries crash on stable/14 (and late 14-current) on the corresponding
> machines. But only in combination with CFLAGS -O2!
>
>
> > In any case, for the above gdb session, try the command "disassemble" to see which particular instruction it crashed on. That may give more information.
>
> Thanks for the hint!
> This came out:
> Program terminated with signal SIGILL, Illegal instruction.
> Privileged opcode.
> #0 0x000000000041e040 in init_yank ()
> (gdb) disassemble
> Dump of assembler code for function init_yank:
> 0x000000000041e030 <+0>: push %rbp
> 0x000000000041e031 <+1>: mov %rsp,%rbp
> 0x000000000041e034 <+4>: vpxor %xmm0,%xmm0,%xmm0
> 0x000000000041e038 <+8>: vmovdqa -0x202c10(%rip),%xmm1 # 0x21b430
> => 0x000000000041e040 <+16>: kxnorw %k0,%k0,%k1
This is AVX512 instruction (some of it subset, probably F), not AVX.
> 0x000000000041e044 <+20>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e04f <+31>: vmovdqa -0x202b77(%rip),%xmm1 # 0x21b4e0
> 0x000000000041e057 <+39>: kxnorw %k0,%k0,%k1
> 0x000000000041e05b <+43>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e066 <+54>: vmovdqa -0x202c5e(%rip),%xmm1 # 0x21b410
> 0x000000000041e06e <+62>: kxnorw %k0,%k0,%k1
> 0x000000000041e072 <+66>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e07d <+77>: vmovdqa -0x202cf5(%rip),%xmm1 # 0x21b390
> 0x000000000041e085 <+85>: kxnorw %k0,%k0,%k1
> 0x000000000041e089 <+89>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e094 <+100>: vmovdqa -0x202b5c(%rip),%xmm1 #
> 0x21b540
> 0x000000000041e09c <+108>: kxnorw %k0,%k0,%k1
> 0x000000000041e0a0 <+112>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e0ab <+123>: vmovdqa -0x202e43(%rip),%xmm1 #
> 0x21b270
> 0x000000000041e0b3 <+131>: kxnorw %k0,%k0,%k1
> 0x000000000041e0b7 <+135>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e0c2 <+146>: vmovdqa -0x202d0a(%rip),%xmm1 #
> 0x21b3c0
> 0x000000000041e0ca <+154>: kxnorw %k0,%k0,%k1
> 0x000000000041e0ce <+158>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e0d9 <+169>: vmovdqa -0x202ac1(%rip),%xmm1 #
> 0x21b620
> 0x000000000041e0e1 <+177>: kxnorw %k0,%k0,%k1
> 0x000000000041e0e5 <+181>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e0f0 <+192>: vmovdqa -0x202d58(%rip),%xmm1 #
> 0x21b3a0
> 0x000000000041e0f8 <+200>: kxnorw %k0,%k0,%k1
> 0x000000000041e0fc <+204>: vpscatterdq %ymm0,0x55f180(,%xmm1,1){%k1}
> 0x000000000041e107 <+215>: movq $0x0,0x1414ee(%rip) # 0x55f600
> <y_regs+1152>
> 0x000000000041e112 <+226>: pop %rbp
> 0x000000000041e113 <+227>: vzeroupper
> 0x000000000041e116 <+230>: ret
> End of assembler dump.
>
> Example is from 'cc -c -I. -Iproto -DHAVE_CONFIG_H -DLIBICONV_PLUG
> -I/usr/local/include -O2 -pipe -march=skylake-avx512 -DLIBICONV_PLUG
> -fstack-protector-strong -fno-strict-aliasing -D_REENTRANT
> -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 -o objects/alloc.o alloc.c'
> with CPU:
> Intel(R) Xeon(R) CPU E3-1275 v6 @ 3.80GHz (3800.00-MHz K8-class CPU)
>
> When I 1st noticed, I checked also much more recent CPUs - with the same
> result - if CPUTUPE is set to any avx-involving optimization together with
> -O2, binaries crash with SIGILL on Haswell, SkyLake, TigerLake...
> My last world/ports builds (sucessfully with CPUTYPE?=ivybridge) were with
> stable-13 (arround 13.1) - and llvm 13 I think - can't remember exactly.
>
> Thanks,
> -harry
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