x/crypto/sha3: build failure on linux/s390x at Go master due to illegal instruction

[toothrot]

https://build.golang.org/log/b664bfe4716a53a4766a8340a2e54fb3673cdca9

SIGILL: illegal instruction
PC=0x149156 m=6 sigcode=2

goroutine 9 [running]:
golang.org/x/crypto/sha3.kimd(0x20, 0xc0000ea380, 0xc00011c000, 0x10000, 0x10000)
	/data/golang/workdir/gopath/src/golang.org/x/crypto/sha3/sha3_s390x.s:17 +0x16 fp=0xc00006fae8 sp=0xc00006fae8 pc=0x149156
golang.org/x/crypto/sha3.(*asmState).Write(0xc0000ea380, 0xc00011c000, 0x10000, 0x10000, 0x0, 0x0, 0x0)
	/data/golang/workdir/gopath/src/golang.org/x/crypto/sha3/sha3_s390x.go:116 +0x1fe fp=0xc00006fb48 sp=0xc00006fae8 pc=0x14246e
golang.org/x/crypto/sha3.TestUnalignedWrite.func1(0x19d4b0, 0x7)
	/data/golang/workdir/gopath/src/golang.org/x/crypto/sha3/sha3_test.go:198 +0x2d4 fp=0xc00006ff48 sp=0xc00006fb48 pc=0x147a74
golang.org/x/crypto/sha3.testUnalignedAndGeneric(...)
	/data/golang/workdir/gopath/src/golang.org/x/crypto/sha3/sha3_test.go:81
golang.org/x/crypto/sha3.TestUnalignedWrite(0xc00009a5a0)
	/data/golang/workdir/gopath/src/golang.org/x/crypto/sha3/sha3_test.go:193 +0x94 fp=0xc00006ff80 sp=0xc00006ff48 pc=0x144864
testing.tRunner(0xc00009a5a0, 0x1a82e0)
	/data/golang/workdir/go/src/testing/testing.go:954 +0xd8 fp=0xc00006ffc8 sp=0xc00006ff80 pc=0xe4a88
runtime.goexit()
	/data/golang/workdir/go/src/runtime/asm_s390x.s:779 +0x2 fp=0xc00006ffc8 sp=0xc00006ffc8 pc=0x79f32
created by testing.(*T).Run
	/data/golang/workdir/go/src/testing/testing.go:1005 +0x34a

goroutine 1 [chan receive]:
testing.(*T).Run(0xc00009a5a0, 0x19fa66, 0x12, 0x1a82e0, 0x1000000000e4a3a)
	/data/golang/workdir/go/src/testing/testing.go:1006 +0x36a
testing.runTests.func1(0xc00009a000)
	/data/golang/workdir/go/src/testing/testing.go:1247 +0x88
testing.tRunner(0xc00009a000, 0xc000070e00)
	/data/golang/workdir/go/src/testing/testing.go:954 +0xd8
testing.runTests(0xc00000c060, 0x2c6de0, 0x8, 0x8, 0x0)
	/data/golang/workdir/go/src/testing/testing.go:1245 +0x2a6
testing.(*M).Run(0xc000096000, 0x0)
	/data/golang/workdir/go/src/testing/testing.go:1162 +0x17c
main.main()
	_testmain.go:84 +0x142

r0   0x20	r1   0xc0000ea380
r2   0xc00011c000	r3   0x10000
r4   0x10000	r5   0xc00011c000
r6   0x10000	r7   0x90
r8   0x0	r9   0xd00
r10  0x0	r11  0x0
r12  0x1c	r13  0xc000001200
r14  0x14246e	r15  0xc00006fae8
pc   0x149156	link 0x14246e
FAIL	golang.org/x/crypto/sha3	0.054s

/cc @FiloSottile @katiehockman

[bradfitz]

@mundaym, is this related of moving the s390x builder to z15?

[mundaym]

@mundaym, is this related of moving the s390x builder to z15?

Probably, I'll take a look.

[gopherbot]

Change https://golang.org/cl/213857 mentions this issue: sha3: fix SHA-3 on s390x when using KIMD instruction

[mundaym]

The SIGILL was due to a bug in the way I rounded down the length of an input to a multiple of the rate suitable for the KIMD instruction. It occurs when more than 3KiB of data is written to the hash at once and the size is not a multiple of the rate. The KIMD instruction doesn't have SHA-3 support on z13 (the old buildlet machine) and the test that is failing now was added after the assembly implementation of SHA-3 was added which is why we didn't see this before.

The fix is simple but generally we should probably add better testing for generic vs. assembly implementations both for amd64 and s390x. That will take me a little while.

[mundaym]

(Note that KIMD won't give an incorrect result, it will always just SIGILL.)