From: Peter Maydell <peter.maydell@linaro.org>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] [Bug 1839325] Re: Go programs crash on qemu-sh4 due to issues with atomics
Date: Fri, 09 Aug 2019 17:22:50 -0000 [thread overview]
Message-ID: <156537137023.17671.1927095889622186018.malone@gac.canonical.com> (raw)
In-Reply-To: 156518306048.32528.10373743991208371347.malonedeb@chaenomeles.canonical.com
I just did an objdump -x of the /usr/lib/sh4-linux-gnu/libgo.so.14,
which will be the shipped version from the Debian package, and in the
section header it has:
24 .bss 000191f8 00fe74ec 00fe74ec 00fd74ec 2**2
ALLOC
and in the symbol table it has:
00ff98f4 l O .bss 00000104 runtime.work
So the compiler has put the 'runtime.work' struct at a non-multiple-of-8
offset into the bss, and it's given the BSS alignment requirements that
are only 4-aligned, not 8-aligned. That means it's random luck whether
the struct gets 8-aligned or not.
This looks to me like it's a bug in the sh4 gccgo --
https://go101.org/article/memory-layout.html says that the first word in
a struct or variable is supposed to be guaranteed to be 8-aligned, so
the compiler needs to align things more strictly than it is currently
doing.
--
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https://bugs.launchpad.net/bugs/1839325
Title:
Go programs crash on qemu-sh4 due to issues with atomics
Status in QEMU:
New
Bug description:
After #1738545 [1] was fixed, Go applications work fine on qemu-arm
but still crash on qemu-sh4. From the backtrace, it looks like an
issue with the atomics in qemu-sh4:
(sid-sh4-sbuild)root@epyc:/# cat hello.go
package main
import "fmt"
func main() {
fmt.Println("hello world")
}
(sid-sh4-sbuild)root@epyc:/# gccgo-9 hello.go -o hello
(sid-sh4-sbuild)root@epyc:/# ./hello
panic: ( runtime runtime.errorString) (0x7f74527c,0x80a038)
fatal error: panic on system stack
panic: ( runtime runtime.errorString) (0x7f74527c,0x80a038)
fatal error: panic on system stack
runtime stack:
runtime..z2finternal..z2fatomic.Load64
../../../src/libgo/go/runtime/internal/atomic/atomic.c:37
runtime_mstart
../../../src/libgo/runtime/proc.c:596
goroutine 1 [running]:
goroutine running on other thread; stack unavailable
runtime stack:
runtime..z2finternal..z2fatomic.Load64
../../../src/libgo/go/runtime/internal/atomic/atomic.c:37
runtime_mstart
../../../src/libgo/runtime/proc.c:596
(sid-sh4-sbuild)root@epyc:/#
The same sample Go program runs fine on my SH7785LCR SH4 evaluation
board:
root@tirpitz:~> uname -a
Linux tirpitz 3.16.7-ckt7 #8 PREEMPT Fri Oct 21 18:47:41 CEST 2016 sh4a GNU/Linux
root@tirpitz:~> cat hello.go
package main
import "fmt"
func main() {
fmt.Println("hello world")
}
root@tirpitz:~> gccgo-9 hello.go -o hello
root@tirpitz:~> ./hello
hello world
root@tirpitz:~>
Please note: In order to be able to reproduce this, one also needs to
revert commit 61dedf2af7 [2], otherwise the Go application crashes
differently:
(sid-sh4-sbuild)root@epyc:/# ./hello
Unhandled trap: 0x180
pc=0x7e5f7f9e sr=0x00000000 pr=0x7ee3d582 fpscr=0x00080004
spc=0x00000000 ssr=0x00000000 gbr=0x7e590480 vbr=0x00000000
sgr=0x00000000 dbr=0x00000000 delayed_pc=0x7e5f7f60 fpul=0x00034f3b
r0=0x008007d4 r1=0x00000000 r2=0xfffe0b2a r3=0x00000002
r4=0x008006e4 r5=0x00872000 r6=0x00200000 r7=0x00000000
r8=0x7f7bca7c r9=0x7fffebd4 r10=0x00800480 r11=0x7f7bc0f0
r12=0x7f7a3fa4 r13=0x008004c0 r14=0x7f7b2238 r15=0x7fffebd0
r16=0x00000000 r17=0x00000000 r18=0x00000000 r19=0x00000000
r20=0x00000000 r21=0x00000000 r22=0x00000000 r23=0x00000000
(sid-sh4-sbuild)root@epyc:/#
> [1] https://bugs.launchpad.net/bugs/1738545
> [2] https://bugs.launchpad.net/bugs/1796520
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next prev parent reply other threads:[~2019-08-09 17:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 13:04 [Qemu-devel] [Bug 1839325] [NEW] Go programs crash on qemu-sh4 due to issues with atomics John Paul Adrian Glaubitz
2019-08-09 15:21 ` [Qemu-devel] [Bug 1839325] " Peter Maydell
2019-08-09 16:35 ` Peter Maydell
2019-08-09 17:22 ` Peter Maydell [this message]
2019-08-09 17:38 ` John Paul Adrian Glaubitz
2019-09-20 15:18 ` Peter Maydell
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