From b396d3882ccccc82e1a3c799c7a291d47c43c2c8 Mon Sep 17 00:00:00 2001 From: Nicolas Lacasse Date: Thu, 23 Jul 2020 10:34:46 -0700 Subject: Port sendfile to vfs2. And do some refactoring of the wait logic in sendfile/splice/tee. Updates #1035 #2923 PiperOrigin-RevId: 322815521 --- pkg/sentry/syscalls/linux/vfs2/splice.go | 321 +++++++++++++++++++++++++------ pkg/sentry/syscalls/linux/vfs2/vfs2.go | 2 +- test/syscalls/BUILD | 2 + 3 files changed, 261 insertions(+), 64 deletions(-) diff --git a/pkg/sentry/syscalls/linux/vfs2/splice.go b/pkg/sentry/syscalls/linux/vfs2/splice.go index 945a364a7..63ab11f8c 100644 --- a/pkg/sentry/syscalls/linux/vfs2/splice.go +++ b/pkg/sentry/syscalls/linux/vfs2/splice.go @@ -15,12 +15,15 @@ package vfs2 import ( + "io" + "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/sentry/arch" "gvisor.dev/gvisor/pkg/sentry/kernel" "gvisor.dev/gvisor/pkg/sentry/kernel/pipe" "gvisor.dev/gvisor/pkg/sentry/vfs" "gvisor.dev/gvisor/pkg/syserror" + "gvisor.dev/gvisor/pkg/usermem" "gvisor.dev/gvisor/pkg/waiter" ) @@ -110,16 +113,20 @@ func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal // Move data. var ( - n int64 - err error - inCh chan struct{} - outCh chan struct{} + n int64 + err error ) + dw := dualWaiter{ + inFile: inFile, + outFile: outFile, + } + defer dw.destroy() for { // If both input and output are pipes, delegate to the pipe - // implementation. Otherwise, exactly one end is a pipe, which we - // ensure is consistently ordered after the non-pipe FD's locks by - // passing the pipe FD as usermem.IO to the non-pipe end. + // implementation. Otherwise, exactly one end is a pipe, which + // we ensure is consistently ordered after the non-pipe FD's + // locks by passing the pipe FD as usermem.IO to the non-pipe + // end. switch { case inIsPipe && outIsPipe: n, err = pipe.Splice(t, outPipeFD, inPipeFD, count) @@ -137,38 +144,15 @@ func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal } else { n, err = inFile.Read(t, outPipeFD.IOSequence(count), vfs.ReadOptions{}) } + default: + panic("not possible") } + if n != 0 || err != syserror.ErrWouldBlock || nonBlock { break } - - // Note that the blocking behavior here is a bit different than the - // normal pattern. Because we need to have both data to read and data - // to write simultaneously, we actually explicitly block on both of - // these cases in turn before returning to the splice operation. - if inFile.Readiness(eventMaskRead)&eventMaskRead == 0 { - if inCh == nil { - inCh = make(chan struct{}, 1) - inW, _ := waiter.NewChannelEntry(inCh) - inFile.EventRegister(&inW, eventMaskRead) - defer inFile.EventUnregister(&inW) - continue // Need to refresh readiness. - } - if err = t.Block(inCh); err != nil { - break - } - } - if outFile.Readiness(eventMaskWrite)&eventMaskWrite == 0 { - if outCh == nil { - outCh = make(chan struct{}, 1) - outW, _ := waiter.NewChannelEntry(outCh) - outFile.EventRegister(&outW, eventMaskWrite) - defer outFile.EventUnregister(&outW) - continue // Need to refresh readiness. - } - if err = t.Block(outCh); err != nil { - break - } + if err = dw.waitForBoth(t); err != nil { + break } } @@ -247,45 +231,256 @@ func Tee(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallCo // Copy data. var ( - inCh chan struct{} - outCh chan struct{} + n int64 + err error ) + dw := dualWaiter{ + inFile: inFile, + outFile: outFile, + } + defer dw.destroy() for { - n, err := pipe.Tee(t, outPipeFD, inPipeFD, count) - if n != 0 { - return uintptr(n), nil, nil + n, err = pipe.Tee(t, outPipeFD, inPipeFD, count) + if n != 0 || err != syserror.ErrWouldBlock || nonBlock { + break + } + if err = dw.waitForBoth(t); err != nil { + break + } + } + if n == 0 { + return 0, nil, err + } + outFile.Dentry().InotifyWithParent(linux.IN_MODIFY, 0, vfs.PathEvent) + return uintptr(n), nil, nil +} + +// Sendfile implements linux system call sendfile(2). +func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { + outFD := args[0].Int() + inFD := args[1].Int() + offsetAddr := args[2].Pointer() + count := int64(args[3].SizeT()) + + inFile := t.GetFileVFS2(inFD) + if inFile == nil { + return 0, nil, syserror.EBADF + } + defer inFile.DecRef() + if !inFile.IsReadable() { + return 0, nil, syserror.EBADF + } + + outFile := t.GetFileVFS2(outFD) + if outFile == nil { + return 0, nil, syserror.EBADF + } + defer outFile.DecRef() + if !outFile.IsWritable() { + return 0, nil, syserror.EBADF + } + + // Verify that the outFile Append flag is not set. + if outFile.StatusFlags()&linux.O_APPEND != 0 { + return 0, nil, syserror.EINVAL + } + + // Verify that inFile is a regular file or block device. This is a + // requirement; the same check appears in Linux + // (fs/splice.c:splice_direct_to_actor). + if stat, err := inFile.Stat(t, vfs.StatOptions{Mask: linux.STATX_TYPE}); err != nil { + return 0, nil, err + } else if stat.Mask&linux.STATX_TYPE == 0 || + (stat.Mode&linux.S_IFMT != linux.S_IFREG && stat.Mode&linux.S_IFMT != linux.S_IFBLK) { + return 0, nil, syserror.EINVAL + } + + // Copy offset if it exists. + offset := int64(-1) + if offsetAddr != 0 { + if inFile.Options().DenyPRead { + return 0, nil, syserror.ESPIPE } - if err != syserror.ErrWouldBlock || nonBlock { + if _, err := t.CopyIn(offsetAddr, &offset); err != nil { return 0, nil, err } + if offset < 0 { + return 0, nil, syserror.EINVAL + } + if offset+count < 0 { + return 0, nil, syserror.EINVAL + } + } + + // Validate count. This must come after offset checks. + if count < 0 { + return 0, nil, syserror.EINVAL + } + if count == 0 { + return 0, nil, nil + } + if count > int64(kernel.MAX_RW_COUNT) { + count = int64(kernel.MAX_RW_COUNT) + } - // Note that the blocking behavior here is a bit different than the - // normal pattern. Because we need to have both data to read and data - // to write simultaneously, we actually explicitly block on both of - // these cases in turn before returning to the tee operation. - if inFile.Readiness(eventMaskRead)&eventMaskRead == 0 { - if inCh == nil { - inCh = make(chan struct{}, 1) - inW, _ := waiter.NewChannelEntry(inCh) - inFile.EventRegister(&inW, eventMaskRead) - defer inFile.EventUnregister(&inW) - continue // Need to refresh readiness. + // Copy data. + var ( + n int64 + err error + ) + dw := dualWaiter{ + inFile: inFile, + outFile: outFile, + } + defer dw.destroy() + outPipeFD, outIsPipe := outFile.Impl().(*pipe.VFSPipeFD) + // Reading from input file should never block, since it is regular or + // block device. We only need to check if writing to the output file + // can block. + nonBlock := outFile.StatusFlags()&linux.O_NONBLOCK != 0 + if outIsPipe { + for n < count { + var spliceN int64 + if offset != -1 { + spliceN, err = inFile.PRead(t, outPipeFD.IOSequence(count), offset, vfs.ReadOptions{}) + offset += spliceN + } else { + spliceN, err = inFile.Read(t, outPipeFD.IOSequence(count), vfs.ReadOptions{}) } - if err := t.Block(inCh); err != nil { - return 0, nil, err + n += spliceN + if err == syserror.ErrWouldBlock && !nonBlock { + err = dw.waitForBoth(t) + } + if err != nil { + break } } - if outFile.Readiness(eventMaskWrite)&eventMaskWrite == 0 { - if outCh == nil { - outCh = make(chan struct{}, 1) - outW, _ := waiter.NewChannelEntry(outCh) - outFile.EventRegister(&outW, eventMaskWrite) - defer outFile.EventUnregister(&outW) - continue // Need to refresh readiness. + } else { + // Read inFile to buffer, then write the contents to outFile. + buf := make([]byte, count) + for n < count { + var readN int64 + if offset != -1 { + readN, err = inFile.PRead(t, usermem.BytesIOSequence(buf), offset, vfs.ReadOptions{}) + offset += readN + } else { + readN, err = inFile.Read(t, usermem.BytesIOSequence(buf), vfs.ReadOptions{}) + } + if readN == 0 && err == io.EOF { + // We reached the end of the file. Eat the + // error and exit the loop. + err = nil + break } - if err := t.Block(outCh); err != nil { - return 0, nil, err + n += readN + if err != nil { + break + } + + // Write all of the bytes that we read. This may need + // multiple write calls to complete. + wbuf := buf[:n] + for len(wbuf) > 0 { + var writeN int64 + writeN, err = outFile.Write(t, usermem.BytesIOSequence(wbuf), vfs.WriteOptions{}) + wbuf = wbuf[writeN:] + if err == syserror.ErrWouldBlock && !nonBlock { + err = dw.waitForOut(t) + } + if err != nil { + // We didn't complete the write. Only + // report the bytes that were actually + // written, and rewind the offset. + notWritten := int64(len(wbuf)) + n -= notWritten + if offset != -1 { + offset -= notWritten + } + break + } + } + if err == syserror.ErrWouldBlock && !nonBlock { + err = dw.waitForBoth(t) } + if err != nil { + break + } + } + } + + if offsetAddr != 0 { + // Copy out the new offset. + if _, err := t.CopyOut(offsetAddr, offset); err != nil { + return 0, nil, err + } + } + + if n == 0 { + return 0, nil, err + } + + inFile.Dentry().InotifyWithParent(linux.IN_ACCESS, 0, vfs.PathEvent) + outFile.Dentry().InotifyWithParent(linux.IN_MODIFY, 0, vfs.PathEvent) + return uintptr(n), nil, nil +} + +// dualWaiter is used to wait on one or both vfs.FileDescriptions. It is not +// thread-safe, and does not take a reference on the vfs.FileDescriptions. +// +// Users must call destroy() when finished. +type dualWaiter struct { + inFile *vfs.FileDescription + outFile *vfs.FileDescription + + inW waiter.Entry + inCh chan struct{} + outW waiter.Entry + outCh chan struct{} +} + +// waitForBoth waits for both dw.inFile and dw.outFile to be ready. +func (dw *dualWaiter) waitForBoth(t *kernel.Task) error { + if dw.inFile.Readiness(eventMaskRead)&eventMaskRead == 0 { + if dw.inCh == nil { + dw.inW, dw.inCh = waiter.NewChannelEntry(nil) + dw.inFile.EventRegister(&dw.inW, eventMaskRead) + // We might be ready now. Try again before blocking. + return nil + } + if err := t.Block(dw.inCh); err != nil { + return err + } + } + return dw.waitForOut(t) +} + +// waitForOut waits for dw.outfile to be read. +func (dw *dualWaiter) waitForOut(t *kernel.Task) error { + if dw.outFile.Readiness(eventMaskWrite)&eventMaskWrite == 0 { + if dw.outCh == nil { + dw.outW, dw.outCh = waiter.NewChannelEntry(nil) + dw.outFile.EventRegister(&dw.outW, eventMaskWrite) + // We might be ready now. Try again before blocking. + return nil } + if err := t.Block(dw.outCh); err != nil { + return err + } + } + return nil +} + +// destroy cleans up resources help by dw. No more calls to wait* can occur +// after destroy is called. +func (dw *dualWaiter) destroy() { + if dw.inCh != nil { + dw.inFile.EventUnregister(&dw.inW) + dw.inCh = nil + } + if dw.outCh != nil { + dw.outFile.EventUnregister(&dw.outW) + dw.outCh = nil } + dw.inFile = nil + dw.outFile = nil } diff --git a/pkg/sentry/syscalls/linux/vfs2/vfs2.go b/pkg/sentry/syscalls/linux/vfs2/vfs2.go index 8f497ecc7..1b2cfad7d 100644 --- a/pkg/sentry/syscalls/linux/vfs2/vfs2.go +++ b/pkg/sentry/syscalls/linux/vfs2/vfs2.go @@ -44,7 +44,7 @@ func Override() { s.Table[23] = syscalls.Supported("select", Select) s.Table[32] = syscalls.Supported("dup", Dup) s.Table[33] = syscalls.Supported("dup2", Dup2) - delete(s.Table, 40) // sendfile + s.Table[40] = syscalls.Supported("sendfile", Sendfile) s.Table[41] = syscalls.Supported("socket", Socket) s.Table[42] = syscalls.Supported("connect", Connect) s.Table[43] = syscalls.Supported("accept", Accept) diff --git a/test/syscalls/BUILD b/test/syscalls/BUILD index c06a75ada..15e5fd223 100644 --- a/test/syscalls/BUILD +++ b/test/syscalls/BUILD @@ -640,11 +640,13 @@ syscall_test( syscall_test( add_overlay = True, test = "//test/syscalls/linux:sendfile_socket_test", + vfs2 = "True", ) syscall_test( add_overlay = True, test = "//test/syscalls/linux:sendfile_test", + vfs2 = "True", ) syscall_test( -- cgit v1.2.3