I changed code a little bit to be able to examine variables:
func GetGroupFD(group int, pciDevice *string) (int, error) {
ioctlId := 0x3b6a
var buffer uintptr
buffer = uintptr(unsafe.Pointer(pciDevice))
device, _, errno := syscall.Syscall(
syscall.SYS_IOCTL,
uintptr(group),
uintptr(unsafe.Pointer(&ioctlId)),
buffer,
)
(gdb) p &buffer
$8 = (uintptr *) 0xc4200c7b88
(gdb) x/g 0xc4200c7b88
0xc4200c7b88: 0x000000c4200c7d08
(gdb) x/g 0x000000c4200c7d08
0xc4200c7d08: 0x000000c4200122d0
(gdb) x/g 0x000000c4200122d0
0xc4200122d0: 0x3a31383a30303030
0x30303030 is start of expected string “0000:81:11.1”, first 4 bytes are not
part of it. Anybody knows where those 4 bytes could have come from? And how to
get rid of them?
Thank you
Serguei
From: <golang-nuts@googlegroups.com> on behalf of Tamás Gulácsi
<tgulacs...@gmail.com>
Date: Thursday, August 23, 2018 at 8:13 AM
To: golang-nuts <golang-nuts@googlegroups.com>
Subject: [go-nuts] Re: Ioctl Syscall with go and c
Is it \0-terminated?
2018. augusztus 23., csütörtök 13:02:13 UTC+2 időpontban sbez...@cisco.com a
következőt írta:
Hello,
I am converting some C code to Go and hit an issue with one particular Syscall:
In C:
device = ioctl(group, 0x3b6a, path);
where path is char[N]
In Go:
ioctlId := 0x3b6a
device, _, errno := syscall.Syscall(
syscall.SYS_IOCTL,
uintptr(group),
uintptr(unsafe.Pointer(&ioctlId)),
uintptr(unsafe.Pointer(pciDevice)),
)
Where pciDevice is *string with exactly the same value as path in C.
When I run Go bits on the same h/w, same OS, same everything, it fails with
"errno 22 (invalid argument)". It seems that the issue is how string gets
passed to Syscall, but I could not find any examples how to do it correctly.
Appreciate some advice here.
Thank you
Serguei
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