Factor fsimpl/gofer.host{Preadv,Pwritev} out of fsimpl/gofer.

Also fix returning EOF when 0 bytes are read.

PiperOrigin-RevId: 308089875

3 files changed, 4 insertions, 69 deletions

diff --git a/pkg/sentry/fsimpl/gofer/BUILD b/pkg/sentry/fsimpl/gofer/BUILD
index acd061905..b9c4beee4 100644
--- a/pkg/sentry/fsimpl/gofer/BUILD
+++ b/pkg/sentry/fsimpl/gofer/BUILD
@@ -35,7 +35,6 @@ go_library(
         "fstree.go",
         "gofer.go",
         "handle.go",
-        "handle_unsafe.go",
         "p9file.go",
         "pagemath.go",
         "regular_file.go",
@@ -53,6 +52,7 @@ go_library(
         "//pkg/p9",
         "//pkg/safemem",
         "//pkg/sentry/fs/fsutil",
+        "//pkg/sentry/hostfd",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/memmap",
diff --git a/pkg/sentry/fsimpl/gofer/handle.go b/pkg/sentry/fsimpl/gofer/handle.go
index cfe66f797..724a3f1f7 100644
--- a/pkg/sentry/fsimpl/gofer/handle.go
+++ b/pkg/sentry/fsimpl/gofer/handle.go
@@ -20,6 +20,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/safemem"
+	"gvisor.dev/gvisor/pkg/sentry/hostfd"
 )
 
 // handle represents a remote "open file descriptor", consisting of an opened
@@ -77,7 +78,7 @@ func (h *handle) readToBlocksAt(ctx context.Context, dsts safemem.BlockSeq, offs
 	}
 	if h.fd >= 0 {
 		ctx.UninterruptibleSleepStart(false)
-		n, err := hostPreadv(h.fd, dsts, int64(offset))
+		n, err := hostfd.Preadv2(h.fd, dsts, int64(offset), 0 /* flags */)
 		ctx.UninterruptibleSleepFinish(false)
 		return n, err
 	}
@@ -103,7 +104,7 @@ func (h *handle) writeFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, o
 	}
 	if h.fd >= 0 {
 		ctx.UninterruptibleSleepStart(false)
-		n, err := hostPwritev(h.fd, srcs, int64(offset))
+		n, err := hostfd.Pwritev2(h.fd, srcs, int64(offset), 0 /* flags */)
 		ctx.UninterruptibleSleepFinish(false)
 		return n, err
 	}
diff --git a/pkg/sentry/fsimpl/gofer/handle_unsafe.go b/pkg/sentry/fsimpl/gofer/handle_unsafe.go
deleted file mode 100644
index 19560ab26..000000000
--- a/pkg/sentry/fsimpl/gofer/handle_unsafe.go
+++ /dev/null
@@ -1,66 +0,0 @@
-// Copyright 2019 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package gofer
-
-import (
-	"syscall"
-	"unsafe"
-
-	"gvisor.dev/gvisor/pkg/safemem"
-)
-
-// Preconditions: !dsts.IsEmpty().
-func hostPreadv(fd int32, dsts safemem.BlockSeq, off int64) (uint64, error) {
-	// No buffering is necessary regardless of safecopy; host syscalls will
-	// return EFAULT if appropriate, instead of raising SIGBUS.
-	if dsts.NumBlocks() == 1 {
-		// Use pread() instead of preadv() to avoid iovec allocation and
-		// copying.
-		dst := dsts.Head()
-		n, _, e := syscall.Syscall6(syscall.SYS_PREAD64, uintptr(fd), dst.Addr(), uintptr(dst.Len()), uintptr(off), 0, 0)
-		if e != 0 {
-			return 0, e
-		}
-		return uint64(n), nil
-	}
-	iovs := safemem.IovecsFromBlockSeq(dsts)
-	n, _, e := syscall.Syscall6(syscall.SYS_PREADV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
-	if e != 0 {
-		return 0, e
-	}
-	return uint64(n), nil
-}
-
-// Preconditions: !srcs.IsEmpty().
-func hostPwritev(fd int32, srcs safemem.BlockSeq, off int64) (uint64, error) {
-	// No buffering is necessary regardless of safecopy; host syscalls will
-	// return EFAULT if appropriate, instead of raising SIGBUS.
-	if srcs.NumBlocks() == 1 {
-		// Use pwrite() instead of pwritev() to avoid iovec allocation and
-		// copying.
-		src := srcs.Head()
-		n, _, e := syscall.Syscall6(syscall.SYS_PWRITE64, uintptr(fd), src.Addr(), uintptr(src.Len()), uintptr(off), 0, 0)
-		if e != 0 {
-			return 0, e
-		}
-		return uint64(n), nil
-	}
-	iovs := safemem.IovecsFromBlockSeq(srcs)
-	n, _, e := syscall.Syscall6(syscall.SYS_PWRITEV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
-	if e != 0 {
-		return 0, e
-	}
-	return uint64(n), nil
-}