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

[SylvainGarrigues]

Is this bug closed with the commit above?

[agnivade]

The bug says "Updates #22448", so it's not done yet.

[paulzhol]

@SylvainGarrigues I did the ino64 change. You now have 64-bit inode support on FreeBSD 12 while on older releases the Stat/Statfs/Dirent return 64-bit inodes but only for compatibility (they use the old non 64-bit aware syscalls and just extend the result to the new format).

There's a new kevent syscall supporting absolute timers (https://svnweb.freebsd.org/base?view=revision&revision=320043) which changes the struct layout, but I don't think there's a requirement to use it on FreeBSD 12 as long as the old COMPAT11 kevent works fine.

I'm not aware of additional incompatible changes, but this issue also calls for additional tests to detect breakage, so I guess we keep it open for a while.

[mikioh]

I'm not aware of additional incompatible changes

If anything, please file a new issue and make a linkage to #22447. I will try to skim the network subsystem code on 12-STABLE during Go 1.12 code freeze, well, by the end of this year.

[gopherbot]

Change https://golang.org/cl/155958 mentions this issue: syscall: revert to pre-FreeBSD 10 / POSIX-2008 timespec field names in Stat_t on FreeBSD

[gopherbot]

Change https://golang.org/cl/160778 mentions this issue: doc: go1.12: document FreeBSD 12.0 requires COMPAT_FREEBSD11