os, syscall, x/sys/unix: add support for FreeBSD 12

[mikioh]

As described in https://svnweb.freebsd.org/base?view=revision&revision=318736, FreeBSD 12 changes the ABI related to file status and directory file format like the following:

--- a/unix/ztypes_freebsd_${goarch}.go
+++ b/unix/ztypes_freebsd_$(goarch}.go
type Stat_t struct {
-       Dev           uint32
-       Ino           uint32
+       Dev           uint64
+       Ino           uint64
        Mode          uint16
-       Nlink         uint16
+       Pad_cgo_0     [6]byte
+       Nlink         uint64
        Uid           uint32
        Gid           uint32
-       Rdev          uint32
+       Rdev          uint64
        Atimespec     Timespec
        Mtimespec     Timespec
        Ctimespec     Timespec

type Statfs_t struct {
        Fsid        Fsid
        Charspare   [80]int8
        Fstypename  [16]int8
-       Mntfromname [88]int8
-       Mntonname   [88]int8
+       Mntfromname [1024]int8
+       Mntonname   [1024]int8
 }
 
 type Dirent struct {
-       Fileno uint32
+       Fileno uint64
+       Off    int64
        Reclen uint16
        Type   uint8
-       Namlen uint8
+       Pad0   uint8
+       Namlen uint16
+       Pad1   uint16
        Name   [256]int8
 }

We need to find out some good way to fill the ABI gap between FreeBSD 11 or below and FreeBSD 12 or above. Plus a few test cases. The existing test cases don't detect the ABI breakage and APIs in os, syscall and x/sys/unix packages return corrupted information to API users.

[gopherbot]

Change https://golang.org/cl/136816 mentions this issue: unix: FreeBSD 12 ino64 support

[paulzhol]

I've sent https://golang.org/cl/136816 to enable 64-bit inodes in x/sys/unix.
Should the syscall package be updated as well (it is frozen)? Stat_t is used in pkg archive/tar, os and internal/poll.

[ianlancetaylor]

It sounds like we have to modify the syscall package for correctness; that is, if we don't modify the syscall package, programs will stop working correctly on unreasonably large file systems. Those kinds of changes to the syscall package are OK.

[paulzhol]

@ianlancetaylor I don't think programs will stop working, I mean we can keep using the COMPAT11 ABI in std, at least while we also support FreeBSD 10 and 11. Please see my #22447 (comment).

[ianlancetaylor]

OK, thanks. In that case, what is the reason for changing?

[emaste]

Avoiding ino64 will result in failures on file systems with an unreasonably large number of inodes (and some other limitations that were addressed w/ ino64, like Mnt*name), but as long as those limits are not being encountered everything will remain functional.

FreeBSD 10's EOL is not far off but FreeBSD 11 has years left. In a couple of years FreeBSD 12 will be the earliest supported release, and all supported releases will have ino64.

[ianlancetaylor]

Thanks. If programs will stop working in some cases, however obscure, then we should change the syscall package. But it doesn't sound like a high priority.

[paulzhol]

Can I take this as a go ahead to send a syscall CL just for the ino64 change, but keeping Kevent/keventt FREEBSD_COMPAT11 (I plan to have type Kevent C.struct_freebsd11_stat_t in the cgo -godefs comments)?

[ianlancetaylor]

@paulzhol Sure, I guess so. I don't know the details of what should change, I'm just saying that change seems appropriate here.

[gopherbot]

Change https://golang.org/cl/138595 mentions this issue: syscall: FreeBSD 12 ino64 support