internal/syscall/unix: add Mkdirat and Readlinkat

For #67002

Change-Id: I460e02db33799c145c296bcf0668fa555199036e
Reviewed-on: https://go-review.googlesource.com/c/go/+/617376
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/internal/syscall/unix/asm_darwin.s

@@ -23,3 +23,5 @@ TEXT ·libc_getgrnam_r_trampoline(SB),NOSPLIT,$0-0; JMP libc_getgrnam_r(SB)
 TEXT ·libc_getgrgid_r_trampoline(SB),NOSPLIT,$0-0; JMP libc_getgrgid_r(SB)
 TEXT ·libc_sysconf_trampoline(SB),NOSPLIT,$0-0; JMP libc_sysconf(SB)
 TEXT ·libc_faccessat_trampoline(SB),NOSPLIT,$0-0; JMP libc_faccessat(SB)
+TEXT ·libc_readlinkat_trampoline(SB),NOSPLIT,$0-0; JMP libc_readlinkat(SB)
+TEXT ·libc_mkdirat_trampoline(SB),NOSPLIT,$0-0; JMP libc_mkdirat(SB)

src/internal/syscall/unix/asm_openbsd.s

@@ -10,3 +10,7 @@ TEXT ·libc_faccessat_trampoline(SB),NOSPLIT,$0-0
         JMP	libc_faccessat(SB)
 TEXT ·libc_arc4random_buf_trampoline(SB),NOSPLIT,$0-0
         JMP	libc_arc4random_buf(SB)
+TEXT ·libc_readlinkat_trampoline(SB),NOSPLIT,$0-0
+        JMP	libc_readlinkat(SB)
+TEXT ·libc_mkdirat_trampoline(SB),NOSPLIT,$0-0
+        JMP	libc_mkdirat(SB)

src/internal/syscall/unix/at.go

@@ -38,3 +38,44 @@ func Openat(dirfd int, path string, flags int, perm uint32) (int, error) {
 
 	return int(fd), nil
 }
+
+func Readlinkat(dirfd int, path string, buf []byte) (int, error) {
+	p0, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return 0, err
+	}
+	var p1 unsafe.Pointer
+	if len(buf) > 0 {
+		p1 = unsafe.Pointer(&buf[0])
+	} else {
+		p1 = unsafe.Pointer(&_zero)
+	}
+	n, _, errno := syscall.Syscall6(readlinkatTrap,
+		uintptr(dirfd),
+		uintptr(unsafe.Pointer(p0)),
+		uintptr(p1),
+		uintptr(len(buf)),
+		0, 0)
+	if errno != 0 {
+		return 0, errno
+	}
+
+	return int(n), nil
+}
+
+func Mkdirat(dirfd int, path string, mode uint32) error {
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+
+	_, _, errno := syscall.Syscall6(mkdiratTrap,
+		uintptr(dirfd),
+		uintptr(unsafe.Pointer(p)),
+		uintptr(mode),
+		0, 0, 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

src/internal/syscall/unix/at_aix.go

@@ -7,6 +7,8 @@ package unix
 //go:cgo_import_dynamic libc_fstatat fstatat "libc.a/shr_64.o"
 //go:cgo_import_dynamic libc_openat openat "libc.a/shr_64.o"
 //go:cgo_import_dynamic libc_unlinkat unlinkat "libc.a/shr_64.o"
+//go:cgo_import_dynamic libc_readlinkat readlinkat "libc.a/shr_64.o"
+//go:cgo_import_dynamic libc_mkdirat mkdirat "libc.a/shr_64.o"
 
 const (
 	AT_EACCESS          = 0x1

src/internal/syscall/unix/at_darwin.go

@@ -0,0 +1,60 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin
+
+package unix
+
+import (
+	"internal/abi"
+	"syscall"
+	"unsafe"
+)
+
+func libc_readlinkat_trampoline()
+
+//go:cgo_import_dynamic libc_readlinkat readlinkat "/usr/lib/libSystem.B.dylib"
+
+func Readlinkat(dirfd int, path string, buf []byte) (int, error) {
+	p0, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return 0, err
+	}
+	var p1 unsafe.Pointer
+	if len(buf) > 0 {
+		p1 = unsafe.Pointer(&buf[0])
+	} else {
+		p1 = unsafe.Pointer(&_zero)
+	}
+	n, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_readlinkat_trampoline),
+		uintptr(dirfd),
+		uintptr(unsafe.Pointer(p0)),
+		uintptr(p1),
+		uintptr(len(buf)),
+		0,
+		0)
+	if errno != 0 {
+		return 0, errno
+	}
+	return int(n), nil
+}
+
+func libc_mkdirat_trampoline()
+
+//go:cgo_import_dynamic libc_mkdirat mkdirat "/usr/lib/libSystem.B.dylib"
+
+func Mkdirat(dirfd int, path string, mode uint32) error {
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+	_, _, errno := syscall_syscall(abi.FuncPCABI0(libc_mkdirat_trampoline),
+		uintptr(dirfd),
+		uintptr(unsafe.Pointer(p)),
+		uintptr(mode))
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

src/internal/syscall/unix/at_libc.go

@@ -14,11 +14,15 @@ import (
 //go:linkname procFstatat libc_fstatat
 //go:linkname procOpenat libc_openat
 //go:linkname procUnlinkat libc_unlinkat
+//go:linkname procReadlinkat libc_readlinkat
+//go:linkname procMkdirat libc_mkdirat
 
 var (
 	procFstatat,
 	procOpenat,
-	procUnlinkat uintptr
+	procUnlinkat,
+	procReadlinkat,
+	procMkdirat uintptr
 )
 
 func Unlinkat(dirfd int, path string, flags int) error {
@@ -62,3 +66,44 @@ func Fstatat(dirfd int, path string, stat *syscall.Stat_t, flags int) error {
 
 	return nil
 }
+
+func Readlinkat(dirfd int, path string, buf []byte) (int, error) {
+	p0, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return 0, err
+	}
+	var p1 unsafe.Pointer
+	if len(buf) > 0 {
+		p1 = unsafe.Pointer(&buf[0])
+	} else {
+		p1 = unsafe.Pointer(&_zero)
+	}
+	n, _, errno := syscall6(uintptr(unsafe.Pointer(&procReadlinkat)), 4,
+		uintptr(dirfd),
+		uintptr(unsafe.Pointer(p0)),
+		uintptr(p1),
+		uintptr(len(buf)),
+		0, 0)
+	if errno != 0 {
+		return 0, errno
+	}
+
+	return int(n), nil
+}
+
+func Mkdirat(dirfd int, path string, mode uint32) error {
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+
+	_, _, errno := syscall6(uintptr(unsafe.Pointer(&procMkdirat)), 3,
+		uintptr(dirfd),
+		uintptr(unsafe.Pointer(p)),
+		uintptr(mode),
+		0, 0, 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

src/internal/syscall/unix/at_openbsd.go

@@ -0,0 +1,51 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build openbsd && !mips64
+
+package unix
+
+import (
+	"internal/abi"
+	"syscall"
+	"unsafe"
+)
+
+//go:cgo_import_dynamic libc_readlinkat readlinkat "libc.so"
+
+func libc_readlinkat_trampoline()
+
+func Readlinkat(dirfd int, path string, buf []byte) (int, error) {
+	p0, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return 0, err
+	}
+	var p1 unsafe.Pointer
+	if len(buf) > 0 {
+		p1 = unsafe.Pointer(&buf[0])
+	} else {
+		p1 = unsafe.Pointer(&_zero)
+	}
+	n, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_readlinkat_trampoline), uintptr(dirfd), uintptr(unsafe.Pointer(p0)), uintptr(p1), uintptr(len(buf)), 0, 0)
+	if errno != 0 {
+		return 0, errno
+	}
+	return int(n), nil
+}
+
+//go:cgo_import_dynamic libc_mkdirat mkdirat "libc.so"
+
+func libc_mkdirat_trampoline()
+
+func Mkdirat(dirfd int, path string, mode uint32) error {
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+	_, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_mkdirat_trampoline), uintptr(dirfd), uintptr(unsafe.Pointer(p)), 0, 0, 0, 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

src/internal/syscall/unix/at_solaris.go

@@ -16,6 +16,8 @@ func rawSyscall6(trap, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, e
 //go:cgo_import_dynamic libc_fstatat fstatat "libc.so"
 //go:cgo_import_dynamic libc_openat openat "libc.so"
 //go:cgo_import_dynamic libc_unlinkat unlinkat "libc.so"
+//go:cgo_import_dynamic libc_readlinkat readlinkat "libc.so"
+//go:cgo_import_dynamic libc_mkdirat mkdirat "libc.so"
 //go:cgo_import_dynamic libc_uname uname "libc.so"
 
 const (

src/internal/syscall/unix/at_sysnum_dragonfly.go

@@ -10,6 +10,8 @@ const (
 	unlinkatTrap   uintptr = syscall.SYS_UNLINKAT
 	openatTrap     uintptr = syscall.SYS_OPENAT
 	fstatatTrap    uintptr = syscall.SYS_FSTATAT
+	readlinkatTrap uintptr = syscall.SYS_READLINKAT
+	mkdiratTrap    uintptr = syscall.SYS_MKDIRAT
 
 	AT_EACCESS          = 0x4
 	AT_FDCWD            = 0xfffafdcd

src/internal/syscall/unix/at_sysnum_freebsd.go

@@ -17,4 +17,6 @@ const (
 	unlinkatTrap       uintptr = syscall.SYS_UNLINKAT
 	openatTrap         uintptr = syscall.SYS_OPENAT
 	posixFallocateTrap uintptr = syscall.SYS_POSIX_FALLOCATE
+	readlinkatTrap     uintptr = syscall.SYS_READLINKAT
+	mkdiratTrap        uintptr = syscall.SYS_MKDIRAT
 )

src/internal/syscall/unix/at_sysnum_linux.go

@@ -6,8 +6,12 @@ package unix
 
 import "syscall"
 
-const unlinkatTrap uintptr = syscall.SYS_UNLINKAT
-const openatTrap uintptr = syscall.SYS_OPENAT
+const (
+	unlinkatTrap   uintptr = syscall.SYS_UNLINKAT
+	openatTrap     uintptr = syscall.SYS_OPENAT
+	readlinkatTrap uintptr = syscall.SYS_READLINKAT
+	mkdiratTrap    uintptr = syscall.SYS_MKDIRAT
+)
 
 const (
 	AT_EACCESS          = 0x200

src/internal/syscall/unix/at_sysnum_netbsd.go

@@ -6,9 +6,13 @@ package unix
 
 import "syscall"
 
-const unlinkatTrap uintptr = syscall.SYS_UNLINKAT
-const openatTrap uintptr = syscall.SYS_OPENAT
-const fstatatTrap uintptr = syscall.SYS_FSTATAT
+const (
+	unlinkatTrap   uintptr = syscall.SYS_UNLINKAT
+	openatTrap     uintptr = syscall.SYS_OPENAT
+	fstatatTrap    uintptr = syscall.SYS_FSTATAT
+	readlinkatTrap uintptr = syscall.SYS_READLINKAT
+	mkdiratTrap    uintptr = syscall.SYS_MKDIRAT
+)
 
 const (
 	AT_EACCESS          = 0x100

src/internal/syscall/unix/at_sysnum_openbsd.go

@@ -6,9 +6,13 @@ package unix
 
 import "syscall"
 
-const unlinkatTrap uintptr = syscall.SYS_UNLINKAT
-const openatTrap uintptr = syscall.SYS_OPENAT
-const fstatatTrap uintptr = syscall.SYS_FSTATAT
+const (
+	unlinkatTrap   uintptr = syscall.SYS_UNLINKAT
+	openatTrap     uintptr = syscall.SYS_OPENAT
+	fstatatTrap    uintptr = syscall.SYS_FSTATAT
+	readlinkatTrap uintptr = syscall.SYS_READLINKAT
+	mkdiratTrap    uintptr = syscall.SYS_MKDIRAT
+)
 
 const (
 	AT_EACCESS          = 0x1

src/internal/syscall/unix/at_wasip1.go

@@ -2,8 +2,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build wasip1
+
 package unix
 
+import (
+	"syscall"
+	"unsafe"
+)
+
 const (
 	// UTIME_OMIT is the sentinel value to indicate that a time value should not
 	// be changed. It is useful for example to indicate for example with UtimesNano
@@ -11,3 +18,46 @@ const (
 	// Its value must match syscall/fs_wasip1.go
 	UTIME_OMIT = -0x2
 )
+
+func Readlinkat(dirfd int, path string, buf []byte) (int, error) {
+	var nwritten size
+	errno := path_readlink(
+		int32(dirfd),
+		unsafe.Pointer(unsafe.StringData(path)),
+		size(len(path)),
+		unsafe.Pointer(&buf[0]),
+		size(len(buf)),
+		unsafe.Pointer(&nwritten))
+	return int(nwritten), errnoErr(errno)
+
+}
+
+type (
+	size = uint32
+)
+
+//go:wasmimport wasi_snapshot_preview1 path_readlink
+//go:noescape
+func path_readlink(fd int32, path unsafe.Pointer, pathLen size, buf unsafe.Pointer, bufLen size, nwritten unsafe.Pointer) syscall.Errno
+
+func Mkdirat(dirfd int, path string, mode uint32) error {
+	if path == "" {
+		return syscall.EINVAL
+	}
+	return errnoErr(path_create_directory(
+		int32(dirfd),
+		unsafe.Pointer(unsafe.StringData(path)),
+		size(len(path)),
+	))
+}
+
+//go:wasmimport wasi_snapshot_preview1 path_create_directory
+//go:noescape
+func path_create_directory(fd int32, path unsafe.Pointer, pathLen size) syscall.Errno
+
+func errnoErr(errno syscall.Errno) error {
+	if errno == 0 {
+		return nil
+	}
+	return errno
+}

src/internal/syscall/unix/syscall.go

@@ -0,0 +1,8 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package unix
+
+// Single-word zero for use when we need a valid pointer to 0 bytes.
+var _zero uintptr

src/internal/syscall/unix/sysnum_linux_386.go

@@ -9,4 +9,5 @@ const (
 	copyFileRangeTrap   uintptr = 377
 	pidfdSendSignalTrap uintptr = 424
 	pidfdOpenTrap       uintptr = 434
+	openat2Trap         uintptr = 437
 )

src/internal/syscall/unix/sysnum_linux_amd64.go

@@ -9,4 +9,5 @@ const (
 	copyFileRangeTrap   uintptr = 326
 	pidfdSendSignalTrap uintptr = 424
 	pidfdOpenTrap       uintptr = 434
+	openat2Trap         uintptr = 437
 )

src/internal/syscall/unix/sysnum_linux_arm.go

@@ -9,4 +9,5 @@ const (
 	copyFileRangeTrap   uintptr = 391
 	pidfdSendSignalTrap uintptr = 424
 	pidfdOpenTrap       uintptr = 434
+	openat2Trap         uintptr = 437
 )

src/internal/syscall/unix/sysnum_linux_generic.go

@@ -15,4 +15,5 @@ const (
 	copyFileRangeTrap   uintptr = 285
 	pidfdSendSignalTrap uintptr = 424
 	pidfdOpenTrap       uintptr = 434
+	openat2Trap         uintptr = 437
 )

src/internal/syscall/unix/sysnum_linux_mips64x.go

@@ -11,4 +11,5 @@ const (
 	copyFileRangeTrap   uintptr = 5320
 	pidfdSendSignalTrap uintptr = 5424
 	pidfdOpenTrap       uintptr = 5434
+	openat2Trap         uintptr = 5437
 )

src/internal/syscall/unix/sysnum_linux_mipsx.go

@@ -11,4 +11,5 @@ const (
 	copyFileRangeTrap   uintptr = 4360
 	pidfdSendSignalTrap uintptr = 4424
 	pidfdOpenTrap       uintptr = 4434
+	openat2Trap         uintptr = 4437
 )

src/internal/syscall/unix/sysnum_linux_ppc64x.go

@@ -11,4 +11,5 @@ const (
 	copyFileRangeTrap   uintptr = 379
 	pidfdSendSignalTrap uintptr = 424
 	pidfdOpenTrap       uintptr = 434
+	openat2Trap         uintptr = 437
 )

src/internal/syscall/unix/sysnum_linux_s390x.go

@@ -9,4 +9,5 @@ const (
 	copyFileRangeTrap   uintptr = 375
 	pidfdSendSignalTrap uintptr = 424
 	pidfdOpenTrap       uintptr = 434
+	openat2Trap         uintptr = 437
 )