gccgo: Go compiled with gcc 8.3 does not start on powerpc-linux-musl

[awilfox]

What version of Go are you using (go version)?

$ go version
fatal error: runtime: cannot reserve arena virtual address space
runtime: panic before malloc heap initialized`

Does this issue reproduce with the latest release?

Yes, this is 8.3.0:

gcc (Adelie 8.3.0) 8.3.0

What operating system and processor architecture are you using (go env)?

Adélie Linux 1.0-BETA3, on 32-bit PowerPC (musl libc, big endian)

What did you do?

Built GCC 8.3 with --enable-languages=c,c++,fortran,go.

What did you expect to see?

A working Go runtime.

What did you see instead?

awilcox on gwyn [pts/3 Sun 3 2:32] ~: go version
fatal error: runtime: cannot reserve arena virtual address space
runtime: panic before malloc heap initialized

runtime stack:

        :0
runtime.throw
        :0
runtime.schedinit
        :0

        :0
libc_start_main_stage2
        src/env/__libc_start_main.c:94

Notes

GCC 6.4 does not crash with that error, instead crashing further in:

fatal error: unexpected signal during runtime execution
[signal 0xb code=0x2 addr=0x20000426]

goroutine 16 [running]:

        :0

        :0

        :0

        :0

        :0

        :0

        :0

        :0

        :0
__go_init_main
        /home/awilcox/hello.go:1

        :0

        :0

        :0
created by main
        /usr/src/packages/system/gcc/src/gcc-6.4.0/libgo/runtime/go-main.c:54

[awilfox]

Output of strace go version:

execve("/usr/bin/go", ["go", "version"], 0xffd3acd4 /* 46 vars */) = 0
set_tid_address(0xf79ad100)             = 23732
open("/etc/ld-musl-powerpc.path", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib/libgo.so.13", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/local/lib/libgo.so.13", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/lib/libgo.so.13", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
fstat64(3, {st_mode=S_IFREG|0755, st_size=20273140, ...}) = 0
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0e\347\320\0\0\0004"..., 936) = 936
mmap2(NULL, 18178048, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0xf6775000
mmap2(0xf75fd000, 2940928, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0xe78000) = 0xf75fd000
mmap2(0xf78ad000, 122880, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xf78ad000
close(3)                                = 0
open("/lib/libz.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
fstat64(3, {st_mode=S_IFREG|0755, st_size=132508, ...}) = 0
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\0\34`\0\0\0004"..., 936) = 936
mmap2(NULL, 200704, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0xf6744000
mmap2(0xf6773000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x1f000) = 0xf6773000
close(3)                                = 0
open("/lib/libucontext.so.0", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
fstat64(3, {st_mode=S_IFREG|0755, st_size=66644, ...}) = 0
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\0\5\20\0\0\0004"..., 936) = 936
mmap2(NULL, 135168, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0xf6723000
mmap2(0xf6742000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0xf000) = 0xf6742000
close(3)                                = 0
open("/lib/libgcc_s.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/local/lib/libgcc_s.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/lib/libgcc_s.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
fstat64(3, {st_mode=S_IFREG|0644, st_size=132336, ...}) = 0
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\0\"\320\0\0\0004"..., 936) = 936
mmap2(NULL, 200704, PROT_READ|PROT_EXEC, MAP_PRIVATE, 3, 0) = 0xf66f2000
mmap2(0xf6721000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x1f000) = 0xf6721000
close(3)                                = 0
mprotect(0xf75fd000, 1736704, PROT_READ) = 0
mprotect(0xf6773000, 4096, PROT_READ)   = 0
mprotect(0xf6742000, 4096, PROT_READ)   = 0
mprotect(0xf6721000, 4096, PROT_READ)   = 0
mprotect(0xa69000, 77824, PROT_READ)    = 0
sched_getaffinity(0, 128, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]) = 32
brk(NULL)                               = 0x10f8000
write(2, "fatal error: ", 13fatal error: )           = 13

Interestingly, it doesn't seem to be calling mmap from sysReserve. Setting a breakpoint on mmap in gdb yielded this interesting trace:

(gdb) bt
#0  __mmap (start=0x600000, len=807411712, prot=0, flags=34, fd=-1, off=27021597898440704) at src/mman/mmap.c:15
#1  0xf785c2b8 in ?? () from /usr/lib/libgo.so.13
#2  0xf785c500 in ?? () from /usr/lib/libgo.so.13
#3  0xf7898414 in runtime.schedinit () from /usr/lib/libgo.so.13
#4  0x00439a44 in ?? ()
#5  0xf7f4004c in libc_start_main_stage2 (main=0x439970, argc=2, argv=0xffffe2e4) at src/env/__libc_start_main.c:94
#6  0xf7f400b8 in __libc_start_main (main=0x439970, argc=2, argv=<optimized out>) at src/env/__libc_start_main.c:85
#7  0x00439adc in ?? ()
#8  0x00439a94 in ?? ()

That value of off is causing musl to set EINVAL. Similar calls for each attempted arena size are seen:

Breakpoint 1, __mmap (start=0x600000, len=538976256, prot=0, flags=34, fd=-1, off=27021597898440704) at src/mman/mmap.c:15
15      in src/mman/mmap.c
(gdb) c
Continuing.

Breakpoint 1, __mmap (start=0x600000, len=404758528, prot=0, flags=34, fd=-1, off=27021597898440704) at src/mman/mmap.c:15
15      in src/mman/mmap.c
(gdb) c
Continuing.

Breakpoint 1, __mmap (start=0x600000, len=270540800, prot=0, flags=34, fd=-1, off=27021597898440704) at src/mman/mmap.c:15
15      in src/mman/mmap.c
(gdb) c

[awilfox]

Changing the definition of sysMmap in go/runtime/mem_gccgo.go to take the correct argument type for musl, a 64-bit signed integer (as off_t is always 64-bit on musl), fixes this crash.

[odeke-em]

Thank you for reporting this issue @awilfox!

Kindly paging @ianlancetaylor @aclements @laboger

[ianlancetaylor]

@awilfox Can you please paste the output of grep off_t */libgo/runtime_sysinfo.go, looking at the generated file runtime_sysinfo.go in the libgo build directory. Thanks.

[awilfox]

It's consistent on every platform. The output matches on our ppc64 and armv7 builders:

awilcox on erin [pts/1 Fri 8 23:22] libgo: grep off_t runtime_sysinfo.go
type _off_t int64

[gopherbot]

Change https://golang.org/cl/170863 mentions this issue: cmd/gopherbot: CC triaged issues to owners