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-rw-r--r--pkg/sentry/syscalls/linux/linux64.go4
-rw-r--r--pkg/sentry/syscalls/linux/sys_splice.go86
2 files changed, 44 insertions, 46 deletions
diff --git a/pkg/sentry/syscalls/linux/linux64.go b/pkg/sentry/syscalls/linux/linux64.go
index ed996ba51..150999fb8 100644
--- a/pkg/sentry/syscalls/linux/linux64.go
+++ b/pkg/sentry/syscalls/linux/linux64.go
@@ -320,8 +320,8 @@ var AMD64 = &kernel.SyscallTable{
272: syscalls.PartiallySupported("unshare", Unshare, "Mount, cgroup namespaces not supported. Network namespaces supported but must be empty.", nil),
273: syscalls.Error("set_robust_list", syserror.ENOSYS, "Obsolete.", nil),
274: syscalls.Error("get_robust_list", syserror.ENOSYS, "Obsolete.", nil),
- 275: syscalls.PartiallySupported("splice", Splice, "Stub implementation.", []string{"gvisor.dev/issue/138"}), // TODO(b/29354098)
- 276: syscalls.ErrorWithEvent("tee", syserror.ENOSYS, "", []string{"gvisor.dev/issue/138"}), // TODO(b/29354098)
+ 275: syscalls.Supported("splice", Splice),
+ 276: syscalls.Supported("tee", Tee),
277: syscalls.PartiallySupported("sync_file_range", SyncFileRange, "Full data flush is not guaranteed at this time.", nil),
278: syscalls.ErrorWithEvent("vmsplice", syserror.ENOSYS, "", []string{"gvisor.dev/issue/138"}), // TODO(b/29354098)
279: syscalls.CapError("move_pages", linux.CAP_SYS_NICE, "", nil), // requires cap_sys_nice (mostly)
diff --git a/pkg/sentry/syscalls/linux/sys_splice.go b/pkg/sentry/syscalls/linux/sys_splice.go
index 8a98fedcb..f0a292f2f 100644
--- a/pkg/sentry/syscalls/linux/sys_splice.go
+++ b/pkg/sentry/syscalls/linux/sys_splice.go
@@ -29,9 +29,8 @@ func doSplice(t *kernel.Task, outFile, inFile *fs.File, opts fs.SpliceOpts, nonB
total int64
n int64
err error
- ch chan struct{}
- inW bool
- outW bool
+ inCh chan struct{}
+ outCh chan struct{}
)
for opts.Length > 0 {
n, err = fs.Splice(t, outFile, inFile, opts)
@@ -43,35 +42,33 @@ func doSplice(t *kernel.Task, outFile, inFile *fs.File, opts fs.SpliceOpts, nonB
break
}
- // Are we a registered waiter?
- if ch == nil {
- ch = make(chan struct{}, 1)
- }
- if !inW && !inFile.Flags().NonBlocking {
- w, _ := waiter.NewChannelEntry(ch)
- inFile.EventRegister(&w, EventMaskRead)
- defer inFile.EventUnregister(&w)
- inW = true // Registered.
- } else if !outW && !outFile.Flags().NonBlocking {
- w, _ := waiter.NewChannelEntry(ch)
- outFile.EventRegister(&w, EventMaskWrite)
- defer outFile.EventUnregister(&w)
- outW = true // Registered.
- }
-
- // Was anything registered? If no, everything is non-blocking.
- if !inW && !outW {
- break
- }
-
- if (!inW || inFile.Readiness(EventMaskRead) != 0) && (!outW || outFile.Readiness(EventMaskWrite) != 0) {
- // Something became ready, try again without blocking.
- continue
+ // 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) == 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
+ }
}
-
- // Block until there's data.
- if err = t.Block(ch); err != nil {
- break
+ if outFile.Readiness(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
+ }
}
}
@@ -149,7 +146,7 @@ func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
Length: count,
SrcOffset: true,
SrcStart: offset,
- }, false)
+ }, outFile.Flags().NonBlocking)
// Copy out the new offset.
if _, err := t.CopyOut(offsetAddr, n+offset); err != nil {
@@ -159,7 +156,7 @@ func Sendfile(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
// Send data using splice.
n, err = doSplice(t, outFile, inFile, fs.SpliceOpts{
Length: count,
- }, false)
+ }, outFile.Flags().NonBlocking)
}
// We can only pass a single file to handleIOError, so pick inFile
@@ -181,12 +178,6 @@ func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
return 0, nil, syserror.EINVAL
}
- // Only non-blocking is meaningful. Note that unlike in Linux, this
- // flag is applied consistently. We will have either fully blocking or
- // non-blocking behavior below, regardless of the underlying files
- // being spliced to. It's unclear if this is a bug or not yet.
- nonBlocking := (flags & linux.SPLICE_F_NONBLOCK) != 0
-
// Get files.
outFile := t.GetFile(outFD)
if outFile == nil {
@@ -200,6 +191,13 @@ func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
}
defer inFile.DecRef()
+ // The operation is non-blocking if anything is non-blocking.
+ //
+ // N.B. This is a rather simplistic heuristic that avoids some
+ // poor edge case behavior since the exact semantics here are
+ // underspecified and vary between versions of Linux itself.
+ nonBlock := inFile.Flags().NonBlocking || outFile.Flags().NonBlocking || (flags&linux.SPLICE_F_NONBLOCK != 0)
+
// Construct our options.
//
// Note that exactly one of the underlying buffers must be a pipe. We
@@ -257,7 +255,7 @@ func Splice(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
}
// Splice data.
- n, err := doSplice(t, outFile, inFile, opts, nonBlocking)
+ n, err := doSplice(t, outFile, inFile, opts, nonBlock)
// See above; inFile is chosen arbitrarily here.
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "splice", inFile)
@@ -275,9 +273,6 @@ func Tee(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallCo
return 0, nil, syserror.EINVAL
}
- // Only non-blocking is meaningful.
- nonBlocking := (flags & linux.SPLICE_F_NONBLOCK) != 0
-
// Get files.
outFile := t.GetFile(outFD)
if outFile == nil {
@@ -301,11 +296,14 @@ func Tee(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallCo
return 0, nil, syserror.EINVAL
}
+ // The operation is non-blocking if anything is non-blocking.
+ nonBlock := inFile.Flags().NonBlocking || outFile.Flags().NonBlocking || (flags&linux.SPLICE_F_NONBLOCK != 0)
+
// Splice data.
n, err := doSplice(t, outFile, inFile, fs.SpliceOpts{
Length: count,
Dup: true,
- }, nonBlocking)
+ }, nonBlock)
// See above; inFile is chosen arbitrarily here.
return uintptr(n), nil, handleIOError(t, n != 0, err, kernel.ERESTARTSYS, "tee", inFile)
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-18 21:25:57 +0000