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wasi: better poll_oneoff + test + compatibility
Signed-off-by: Gaukas Wang <i@gaukas.wang> wasi: better poll_oneoff Signed-off-by: Gaukas Wang <i@gaukas.wang> fix: poll_oneoff test behavior * Adjust expected event order in a testcase since clock events are now acknowledged outside the loop. * Always write nevents=0 first before start polling to detect faulty memory early. * Poll on blocking stdin FdRead. * Minor nits including if-else criteria/order. Signed-off-by: Gaukas Wang <i@gaukas.wang>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,252 @@ | ||
| //go:build (linux || darwin || windows) && !tinygo | ||
|
|
||
| // Copyright 2024 The WATER Authors. All rights reserved. | ||
| // Use of this source code is governed by Apache 2 license | ||
| // that can be found in the LICENSE file. | ||
|
|
||
| package wasi_snapshot_preview1 | ||
|
|
||
| import ( | ||
| "context" | ||
| "time" | ||
|
|
||
| "github.com/tetratelabs/wazero/api" | ||
| "github.com/tetratelabs/wazero/experimental/sys" | ||
| "github.com/tetratelabs/wazero/internal/fsapi" | ||
| internalsys "github.com/tetratelabs/wazero/internal/sys" | ||
| internalsysfs "github.com/tetratelabs/wazero/internal/sysfs" | ||
| "github.com/tetratelabs/wazero/internal/wasip1" | ||
| "github.com/tetratelabs/wazero/internal/wasm" | ||
| ) | ||
|
|
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| // use the init function to override the default pollOneoffFn | ||
| func init() { | ||
| // override the default pollOneoff | ||
| pollOneoff = newHostFunc( | ||
| wasip1.PollOneoffName, alternativePollOneoffFn, | ||
| []api.ValueType{i32, i32, i32, i32}, | ||
| "in", "out", "nsubscriptions", "result.nevents", | ||
| ) | ||
| } | ||
|
|
||
| // alternativePollOneoffFn is a modified version of pollOneoffFn that | ||
| // tries to be more syscall-aligned. It should block and return only when | ||
| // there is at least one event triggered. | ||
| func alternativePollOneoffFn(_ context.Context, mod api.Module, params []uint64) sys.Errno { | ||
| in := uint32(params[0]) | ||
| out := uint32(params[1]) | ||
| nsubscriptions := uint32(params[2]) | ||
| resultNevents := uint32(params[3]) | ||
|
|
||
| if nsubscriptions == 0 { | ||
| return sys.EINVAL // early returning on empty subscriptions list | ||
| } | ||
|
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| mem := mod.Memory() | ||
|
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||
| // Ensure capacity prior to the read loop to reduce error handling. | ||
| inBuf, ok := mem.Read(in, nsubscriptions*48) | ||
| if !ok { | ||
| return sys.EFAULT | ||
| } | ||
| outBuf, ok := mem.Read(out, nsubscriptions*32) | ||
| // zero-out all buffer before writing | ||
| for i := range outBuf { | ||
| outBuf[i] = 0 | ||
| } | ||
|
|
||
| if !ok { | ||
| return sys.EFAULT | ||
| } | ||
|
|
||
| // start by writing 0 to resultNevents | ||
| if !mod.Memory().WriteUint32Le(resultNevents, 0) { | ||
| return sys.EFAULT | ||
| } | ||
|
|
||
| // Extract FS context, used in the body of the for loop for FS access. | ||
| fsc := mod.(*wasm.ModuleInstance).Sys.FS() | ||
| // Slice of events that are processed out of the loop (blocking stdin subscribers). | ||
| var blockingStdinSubs []*event | ||
| // The timeout is initialized at max Duration, the loop will find the minimum. | ||
| var timeout time.Duration = 1<<63 - 1 | ||
| // Count of all the subscriptions that have been already written back to outBuf. | ||
| // nevents*32 returns at all times the offset where the next event should be written: | ||
| // this way we ensure that there are no gaps between records. | ||
| var nevents uint32 | ||
|
|
||
| // Slice of all I/O events that will be written if triggered | ||
| var ioEvents []*event | ||
|
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| // Slice of hostPollSub that will be used for polling | ||
| var hostPollSubs []internalsysfs.PollFd | ||
|
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| // The clock event with the minimum timeout, if any. | ||
| var clkevent *event | ||
|
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| // Layout is subscription_u: Union | ||
| // https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md#subscription_u | ||
| for i := uint32(0); i < nsubscriptions; i++ { | ||
| inOffset := i * 48 | ||
| outOffset := nevents * 32 | ||
|
|
||
| eventType := inBuf[inOffset+8] // +8 past userdata | ||
| // +8 past userdata +8 contents_offset | ||
| argBuf := inBuf[inOffset+8+8:] | ||
| userData := inBuf[inOffset : inOffset+8] | ||
|
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| evt := &event{ | ||
| eventType: eventType, | ||
| userData: userData, | ||
| errno: wasip1.ErrnoSuccess, | ||
| } | ||
|
|
||
| switch eventType { | ||
| case wasip1.EventTypeClock: // handle later | ||
| newTimeout, err := processClockEvent(argBuf) | ||
| if err != 0 { | ||
| return err | ||
| } | ||
| // Min timeout. | ||
| if newTimeout < timeout { | ||
| timeout = newTimeout | ||
| // overwrite the clock event | ||
| clkevent = evt | ||
| } | ||
| case wasip1.EventTypeFdRead: | ||
| guestFd := int32(le.Uint32(argBuf)) | ||
| if guestFd < 0 { | ||
| return sys.EBADF | ||
| } | ||
|
|
||
| if file, ok := fsc.LookupFile(guestFd); !ok { | ||
| evt.errno = wasip1.ErrnoBadf | ||
| writeEvent(outBuf[outOffset:], evt) | ||
| nevents++ | ||
| } else if guestFd == internalsys.FdStdin { // stdin is always checked with Poll function later. | ||
| if file.File.IsNonblock() { // non-blocking stdin is always ready to read | ||
| writeEvent(outBuf[outOffset:], evt) | ||
| nevents++ | ||
| } else { | ||
| // if the fd is Stdin, and it is in blocking mode, | ||
| // do not ack yet, append to a slice for delayed evaluation. | ||
| blockingStdinSubs = append(blockingStdinSubs, evt) | ||
| } | ||
| } else if hostFd := file.File.Fd(); hostFd == 0 { | ||
| evt.errno = wasip1.ErrnoNotsup | ||
| writeEvent(outBuf[outOffset:], evt) | ||
| nevents++ | ||
| } else { | ||
| ioEvents = append(ioEvents, evt) | ||
| hostPollSubs = append(hostPollSubs, internalsysfs.PollFd{ | ||
| Fd: hostFd, | ||
| Events: fsapi.POLLIN, | ||
| }) | ||
| } | ||
| case wasip1.EventTypeFdWrite: | ||
| guestFd := int32(le.Uint32(argBuf)) | ||
| if guestFd < 0 { | ||
| return sys.EBADF | ||
| } | ||
|
|
||
| if file, ok := fsc.LookupFile(guestFd); !ok { | ||
| evt.errno = wasip1.ErrnoBadf | ||
| writeEvent(outBuf[outOffset:], evt) | ||
| nevents++ | ||
| } else if guestFd == internalsys.FdStdout || guestFd == internalsys.FdStderr { // stdout and stderr are always ready to write | ||
| writeEvent(outBuf[outOffset:], evt) | ||
| nevents++ | ||
| } else if hostFd := file.File.Fd(); hostFd == 0 { | ||
| evt.errno = wasip1.ErrnoNotsup | ||
| writeEvent(outBuf[outOffset:], evt) | ||
| nevents++ | ||
| } else { | ||
| ioEvents = append(ioEvents, evt) | ||
| hostPollSubs = append(hostPollSubs, internalsysfs.PollFd{ | ||
| Fd: hostFd, | ||
| Events: fsapi.POLLOUT, | ||
| }) | ||
| } | ||
| default: | ||
| return sys.EINVAL | ||
| } | ||
| } | ||
|
|
||
| // We have scanned all the subscriptions, and there are several cases: | ||
| // - Clock subscriptions-only: we block until the timeout expires. | ||
| // - At least one I/O subscription: we call poll on the I/O fds. Then we check the poll results | ||
| // and write back the corresponding events ONLY if the revent in pollFd is properly set. | ||
| // - If no clock subscription, we block with max timeout. | ||
| // - If there are clock subscriptions, we block with the minimum timeout. | ||
|
|
||
| // If there are no I/O subscriptions, we can block until the timeout expires. | ||
| sysCtx := mod.(*wasm.ModuleInstance).Sys | ||
| if len(ioEvents) == 0 { | ||
| if timeout > 0 && clkevent != nil { // there is a clock subscription with a timeout | ||
| sysCtx.Nanosleep(int64(timeout)) | ||
| } | ||
| // Ack the clock event if there is one | ||
| if clkevent != nil { | ||
| writeEvent(outBuf[nevents*32:], clkevent) | ||
| nevents++ | ||
| } | ||
| } | ||
|
|
||
| // If there are I/O subscriptions, we call poll on the I/O fds with the updated timeout. | ||
| if len(hostPollSubs) > 0 { | ||
| pollNevents, err := internalsysfs.Poll(hostPollSubs, int32(timeout.Milliseconds())) | ||
| if err != 0 { | ||
| return err | ||
| } | ||
|
|
||
| if pollNevents > 0 { // if there are events triggered | ||
| // iterate over hostPollSubs and if the revent is set, write back | ||
| // the event | ||
| for i, pollFd := range hostPollSubs { | ||
| if pollFd.Revents&pollFd.Events != 0 { | ||
| // write back the event | ||
| writeEvent(outBuf[nevents*32:], ioEvents[i]) | ||
| nevents++ | ||
| } else if pollFd.Revents != 0 { | ||
| // write back the event | ||
| writeEvent(outBuf[nevents*32:], ioEvents[i]) | ||
| nevents++ | ||
| } | ||
| } | ||
| } else { // otherwise it means that the timeout expired | ||
| // Ack the clock event if there is one (it can also be a default max timeout) | ||
| if clkevent != nil { | ||
| writeEvent(outBuf[nevents*32:], clkevent) | ||
| nevents++ | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // If there are blocking stdin subscribers, check for data with given timeout. | ||
| if len(blockingStdinSubs) > 0 { | ||
| stdin, ok := fsc.LookupFile(internalsys.FdStdin) | ||
| if !ok { | ||
| return sys.EBADF | ||
| } | ||
|
|
||
| // Wait for the timeout to expire, or for some data to become available on Stdin. | ||
| if stdinReady, errno := stdin.File.Poll(fsapi.POLLIN, int32(timeout.Milliseconds())); errno != 0 { | ||
| return errno | ||
| } else if stdinReady { | ||
| // stdin has data ready to for reading, write back all the events | ||
| for i := range blockingStdinSubs { | ||
| evt := blockingStdinSubs[i] | ||
| evt.errno = 0 | ||
| writeEvent(outBuf[nevents*32:], evt) | ||
| nevents++ | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // write nevents to resultNevents | ||
| if !mem.WriteUint32Le(resultNevents, nevents) { | ||
| return sys.EFAULT | ||
| } | ||
|
|
||
| return 0 | ||
| } |
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