syscall: use SYS_GETDENTS64 on linux/mips64{,le}

The getdents64 syscall is only available for mips64/mips64le starting
with Linux kernel 3.10. Since mips64le requires at least 4.8 according
to [1] (regarding #16848) using it should be fine.

[1] https://golang.org/wiki/MinimumRequirements

This CL changes the binary layout of type Dirent for mips64/mips64le,
but not the public API. But since the currently used layout doesn't
match the struct linux_dirent returned by the getdents syscall this
should be fine as well.

Fixes #23624

Change-Id: Iaa7306fa6e4442ad2fed41c60b37627a7314f117
Reviewed-on: https://go-review.googlesource.com/91055
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/syscall/syscall_linux.go

@@ -831,7 +831,7 @@ func Mount(source string, target string, fstype string, flags uintptr, data stri
 //sys	Fdatasync(fd int) (err error)
 //sys	Flock(fd int, how int) (err error)
 //sys	Fsync(fd int) (err error)
-//sys	Getdents(fd int, buf []byte) (n int, err error) = _SYS_getdents
+//sys	Getdents(fd int, buf []byte) (n int, err error) = SYS_GETDENTS64
 //sysnb	Getpgid(pid int) (pgid int, err error)
 
 func Getpgrp() (pid int) {

src/syscall/syscall_linux_386.go

@@ -11,7 +11,6 @@ import "unsafe"
 
 const (
 	_SYS_dup       = SYS_DUP2
-	_SYS_getdents  = SYS_GETDENTS64
 	_SYS_setgroups = SYS_SETGROUPS32
 )
 

src/syscall/syscall_linux_amd64.go

@@ -6,7 +6,6 @@ package syscall
 
 const (
 	_SYS_dup       = SYS_DUP2
-	_SYS_getdents  = SYS_GETDENTS64
 	_SYS_setgroups = SYS_SETGROUPS
 )
 

src/syscall/syscall_linux_arm.go

@@ -8,7 +8,6 @@ import "unsafe"
 
 const (
 	_SYS_dup       = SYS_DUP2
-	_SYS_getdents  = SYS_GETDENTS64
 	_SYS_setgroups = SYS_SETGROUPS32
 )
 

src/syscall/syscall_linux_arm64.go

@@ -6,7 +6,6 @@ package syscall
 
 const (
 	_SYS_dup       = SYS_DUP3
-	_SYS_getdents  = SYS_GETDENTS64
 	_SYS_setgroups = SYS_SETGROUPS
 )
 

src/syscall/syscall_linux_mips64x.go

@@ -8,14 +8,7 @@
 package syscall
 
 const (
-	_SYS_dup = SYS_DUP2
-
-	// Linux introduced getdents64 syscall for N64 ABI only in 3.10
-	// (May 21 2013, rev dec33abaafc89bcbd78f85fad0513170415a26d5),
-	// to support older kernels, we have to use getdents for mips64.
-	// Also note that struct dirent is different for these two.
-	// Lookup linux_dirent{,64} in kernel source code for details.
-	_SYS_getdents  = SYS_GETDENTS
+	_SYS_dup       = SYS_DUP2
 	_SYS_setgroups = SYS_SETGROUPS
 )
 

src/syscall/syscall_linux_mipsx.go

@@ -11,7 +11,6 @@ import "unsafe"
 
 const (
 	_SYS_dup       = SYS_DUP2
-	_SYS_getdents  = SYS_GETDENTS64
 	_SYS_setgroups = SYS_SETGROUPS
 )
 

src/syscall/syscall_linux_ppc64x.go

@@ -9,7 +9,6 @@ package syscall
 
 const (
 	_SYS_dup       = SYS_DUP2
-	_SYS_getdents  = SYS_GETDENTS64
 	_SYS_setgroups = SYS_SETGROUPS
 )
 

src/syscall/syscall_linux_s390x.go

@@ -8,7 +8,6 @@ import "unsafe"
 
 const (
 	_SYS_dup       = SYS_DUP2
-	_SYS_getdents  = SYS_GETDENTS64
 	_SYS_setgroups = SYS_SETGROUPS
 )
 

src/syscall/zsyscall_linux_386.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_amd64.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_arm.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_arm64.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_mips.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_mips64.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_mips64le.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_mipsle.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_ppc64.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_ppc64le.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/zsyscall_linux_s390x.go

@@ -479,7 +479,7 @@ func Getdents(fd int, buf []byte) (n int, err error) {
 	} else {
 		_p0 = unsafe.Pointer(&_zero)
 	}
-	r0, _, e1 := Syscall(_SYS_getdents, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
+	r0, _, e1 := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(_p0), uintptr(len(buf)))
 	n = int(r0)
 	if e1 != 0 {
 		err = errnoErr(e1)

src/syscall/ztypes_linux_mips64.go

@@ -130,15 +130,12 @@ type Statfs_t struct {
 	Spare   [5]int64
 }
 
-// Note: on mips64, we're using the getdents syscall,
-// so the Dirent struct is different.
-
 type Dirent struct {
 	Ino       uint64
 	Off       int64
 	Reclen    uint16
-	Name      [256]int8
 	Type      uint8
+	Name      [256]int8
 	Pad_cgo_0 [5]byte
 }
 

src/syscall/ztypes_linux_mips64le.go

@@ -130,15 +130,12 @@ type Statfs_t struct {
 	Spare   [5]int64
 }
 
-// Note: on mips64, we're using the getdents syscall,
-// so the Dirent struct is different.
-
 type Dirent struct {
 	Ino       uint64
 	Off       int64
 	Reclen    uint16
-	Name      [256]int8
 	Type      uint8
+	Name      [256]int8
 	Pad_cgo_0 [5]byte
 }