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emulator_linux_helpers.go
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emulator_linux_helpers.go
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package mimic
import (
"errors"
"fmt"
"syscall"
"time"
"github.com/cilium/ebpf"
"github.com/cilium/ebpf/asm"
)
// HelperFunction is a function defined in Go which can be invoked by the eBPF VM via the Call instruction.
// The emulator has a lookup map which maps a particular number to a helper function. Helper functions are used as a
// interface between the sandboxed eBPF VM and the Emulator/Host/Outside world. Helper functions are responsible for
// security checks and should implement policies or other forms of limitations to guarantee that eBPF code can't be used
// for malicious purposes.
//
// Helper functions are called with eBPF calling convention, meaning R1-R5 are arguments, and R0 is the return value.
// Errors returned by the helper are considered fatal for the process, are passed to the process and will result in it
// aborting. Recoverable errors/graceful errors should be returned to the VM via the R0 register and a helper func
// specific contract.
type HelperFunction func(p *Process) error
var (
// A mapping of emulated helper functions, functions in this list MAY be replayed with the emulated version as
// fallback, or replaying may not be possible at all.
emulatedLinuxHelpers = []HelperFunction{
0: nil, // 0 is not a valid helper function
asm.FnMapLookupElem: linuxHelperMapLookupElem,
asm.FnMapUpdateElem: linuxHelperMapUpdateElem,
asm.FnMapDeleteElem: linuxHelperMapDeleteElem,
asm.FnProbeRead: linuxHelperCantEmulate,
asm.FnKtimeGetNs: linuxHelperGetKTimeNs,
asm.FnGetPrandomU32: linuxHelperGetPRandomU32,
asm.FnGetSmpProcessorId: linuxHelperGetSmpProcessorID,
asm.FnSkbStoreBytes: linuxHelperSKBStoreBytes,
asm.FnL3CsumReplace: nil, // TODO
asm.FnL4CsumReplace: nil, // TODO
asm.FnTailCall: linuxHelperTailcall,
asm.FnCloneRedirect: nil, // TODO
asm.FnGetCurrentPidTgid: linuxHelperCantEmulate,
asm.FnGetCurrentUidGid: linuxHelperCantEmulate,
asm.FnGetCurrentComm: linuxHelperCantEmulate,
asm.FnGetCgroupClassid: linuxHelperCantEmulate,
asm.FnSkbVlanPush: nil, // TODO
asm.FnSkbVlanPop: nil, // TODO
asm.FnSkbGetTunnelKey: nil, // TODO
asm.FnSkbSetTunnelKey: nil, // TODO
asm.FnPerfEventRead: linuxHelperCantEmulate,
asm.FnRedirect: nil, // TODO
asm.FnGetRouteRealm: linuxHelperCantEmulate,
asm.FnPerfEventOutput: linuxHelperEventOutput,
asm.FnSkbLoadBytes: nil, // TODO
asm.FnGetStackid: linuxHelperCantEmulate,
asm.FnCsumDiff: nil, // TODO
asm.FnSkbGetTunnelOpt: nil, // TODO
asm.FnSkbSetTunnelOpt: nil, // TODO
asm.FnSkbChangeProto: nil, // TODO
asm.FnSkbChangeType: nil, // TODO
asm.FnSkbUnderCgroup: nil, // TODO
asm.FnGetHashRecalc: nil, // TODO
asm.FnGetCurrentTask: linuxHelperCantEmulate,
asm.FnProbeWriteUser: linuxHelperCantEmulate,
asm.FnCurrentTaskUnderCgroup: nil, // TODO
asm.FnSkbChangeTail: linuxHelperSkbChangeTail, // TODO
asm.FnSkbPullData: nil, // TODO
asm.FnCsumUpdate: nil, // TODO
asm.FnSetHashInvalid: nil, // TODO
asm.FnGetNumaNodeId: linuxHelperCantEmulate,
asm.FnSkbChangeHead: nil, // TODO
asm.FnXdpAdjustHead: nil, // TODO
asm.FnProbeReadStr: linuxHelperCantEmulate,
asm.FnGetSocketCookie: linuxHelperCantEmulate,
asm.FnGetSocketUid: linuxHelperCantEmulate,
asm.FnSetHash: nil, // TODO
asm.FnSetsockopt: nil, // TODO
asm.FnSkbAdjustRoom: nil, // TODO
asm.FnRedirectMap: nil, // TODO
asm.FnSkRedirectMap: nil, // TODO
asm.FnSockMapUpdate: nil, // TODO
asm.FnXdpAdjustMeta: nil, // TODO
asm.FnPerfEventReadValue: linuxHelperCantEmulate,
asm.FnPerfProgReadValue: linuxHelperCantEmulate,
asm.FnGetsockopt: nil, // TODO
asm.FnOverrideReturn: nil, // TODO
asm.FnSockOpsCbFlagsSet: nil, // TODO
asm.FnMsgRedirectMap: nil, // TODO
asm.FnMsgApplyBytes: nil, // TODO
asm.FnMsgCorkBytes: nil, // TODO
asm.FnMsgPullData: nil, // TODO
asm.FnBind: nil, // TODO
asm.FnXdpAdjustTail: linuxHelperXDPAdjustTail,
asm.FnSkbGetXfrmState: nil, // TODO
asm.FnGetStack: linuxHelperCantEmulate,
asm.FnSkbLoadBytesRelative: nil, // TODO
asm.FnFibLookup: linuxHelperCantEmulate,
asm.FnSockHashUpdate: nil, // TODO
asm.FnMsgRedirectHash: nil, // TODO
asm.FnSkRedirectHash: nil, // TODO
asm.FnLwtPushEncap: nil, // TODO
asm.FnLwtSeg6StoreBytes: nil, // TODO
asm.FnLwtSeg6AdjustSrh: nil, // TODO
asm.FnLwtSeg6Action: nil, // TODO
asm.FnRcRepeat: nil, // TODO
asm.FnRcKeydown: nil, // TODO
asm.FnSkbCgroupId: nil, // TODO
asm.FnGetCurrentCgroupId: linuxHelperCantEmulate,
asm.FnGetLocalStorage: nil, // TODO
asm.FnSkSelectReuseport: nil, // TODO
asm.FnSkbAncestorCgroupId: nil, // TODO
asm.FnSkLookupTcp: nil, // TODO
asm.FnSkLookupUdp: nil, // TODO
asm.FnSkRelease: nil, // TODO
asm.FnMapPushElem: linuxHelperMapPushElem,
asm.FnMapPopElem: linuxHelperMapPopElem,
asm.FnMapPeekElem: linuxHelperMapPeekElem,
asm.FnMsgPushData: nil, // TODO
asm.FnMsgPopData: nil, // TODO
asm.FnRcPointerRel: nil, // TODO
asm.FnSpinLock: nil, // TODO
asm.FnSpinUnlock: nil, // TODO
asm.FnSkFullsock: nil, // TODO
asm.FnTcpSock: nil, // TODO
asm.FnSkbEcnSetCe: nil, // TODO
asm.FnGetListenerSock: nil, // TODO
asm.FnSkcLookupTcp: nil, // TODO
asm.FnTcpCheckSyncookie: nil, // TODO
asm.FnSysctlGetName: nil, // TODO
asm.FnSysctlGetCurrentValue: nil, // TODO
asm.FnSysctlGetNewValue: nil, // TODO
asm.FnSysctlSetNewValue: nil, // TODO
asm.FnStrtol: nil, // TODO
asm.FnStrtoul: nil, // TODO
asm.FnSkStorageGet: nil, // TODO
asm.FnSkStorageDelete: nil, // TODO
asm.FnSendSignal: nil, // TODO
asm.FnTcpGenSyncookie: nil, // TODO
asm.FnSkbOutput: nil, // TODO
asm.FnProbeReadUser: linuxHelperCantEmulate,
asm.FnProbeReadKernel: linuxHelperCantEmulate,
asm.FnProbeReadUserStr: linuxHelperCantEmulate,
asm.FnProbeReadKernelStr: linuxHelperCantEmulate,
asm.FnTcpSendAck: nil, // TODO
asm.FnSendSignalThread: nil, // TODO
asm.FnJiffies64: nil, // TODO
asm.FnReadBranchRecords: linuxHelperCantEmulate,
asm.FnGetNsCurrentPidTgid: linuxHelperCantEmulate,
asm.FnXdpOutput: nil, // TODO
asm.FnGetNetnsCookie: linuxHelperCantEmulate,
asm.FnGetCurrentAncestorCgroupId: linuxHelperCantEmulate,
asm.FnSkAssign: nil, // TODO
asm.FnKtimeGetBootNs: linuxHelperGetKTimeNs,
asm.FnSeqPrintf: nil, // TODO
asm.FnSeqWrite: nil, // TODO
asm.FnSkCgroupId: linuxHelperCantEmulate,
asm.FnSkAncestorCgroupId: linuxHelperCantEmulate,
asm.FnRingbufOutput: nil, // TODO
asm.FnRingbufReserve: nil, // TODO
asm.FnRingbufSubmit: nil, // TODO
asm.FnRingbufDiscard: nil, // TODO
asm.FnRingbufQuery: nil, // TODO
asm.FnCsumLevel: nil, // TODO
asm.FnSkcToTcp6Sock: nil, // TODO
asm.FnSkcToTcpSock: nil, // TODO
asm.FnSkcToTcpTimewaitSock: nil, // TODO
asm.FnSkcToTcpRequestSock: nil, // TODO
asm.FnSkcToUdp6Sock: nil, // TODO
asm.FnGetTaskStack: linuxHelperCantEmulate,
asm.FnLoadHdrOpt: nil, // TODO
asm.FnStoreHdrOpt: nil, // TODO
asm.FnReserveHdrOpt: nil, // TODO
asm.FnInodeStorageGet: nil, // TODO
asm.FnInodeStorageDelete: nil, // TODO
asm.FnDPath: nil, // TODO
asm.FnCopyFromUser: linuxHelperCantEmulate,
asm.FnSnprintfBtf: nil, // TODO
asm.FnSeqPrintfBtf: nil, // TODO
asm.FnSkbCgroupClassid: linuxHelperCantEmulate,
asm.FnRedirectNeigh: nil, // TODO
asm.FnPerCpuPtr: nil, // TODO
asm.FnThisCpuPtr: nil, // TODO
asm.FnRedirectPeer: nil, // TODO
asm.FnTaskStorageGet: nil, // TODO
asm.FnTaskStorageDelete: nil, // TODO
asm.FnGetCurrentTaskBtf: nil, // TODO
asm.FnBprmOptsSet: nil, // TODO
asm.FnKtimeGetCoarseNs: linuxHelperGetKTimeNs,
asm.FnImaInodeHash: nil, // TODO
asm.FnSockFromFile: nil, // TODO
asm.FnCheckMtu: nil, // TODO
asm.FnForEachMapElem: nil, // TODO
asm.FnSnprintf: nil, // TODO
asm.FnSysBpf: nil, // TODO
asm.FnBtfFindByNameKind: nil, // TODO
asm.FnSysClose: nil, // TODO
asm.FnTimerInit: nil, // TODO
asm.FnTimerSetCallback: nil, // TODO
asm.FnTimerStart: nil, // TODO
asm.FnTimerCancel: nil, // TODO
asm.FnGetFuncIp: nil, // TODO
asm.FnGetAttachCookie: nil, // TODO
asm.FnTaskPtRegs: nil, // TODO
}
// A list of helper functions which can be replayed, functions not in this list MUST be emulated due to side
// effects.
replayableHelpers = []bool{
0: false, // 0 is not a valid helper function
asm.FnMapLookupElem: false,
asm.FnMapUpdateElem: false,
asm.FnMapDeleteElem: false,
asm.FnProbeRead: true,
asm.FnKtimeGetNs: true,
asm.FnTracePrintk: false,
asm.FnGetPrandomU32: true,
asm.FnGetSmpProcessorId: true,
asm.FnSkbStoreBytes: false,
asm.FnL3CsumReplace: false,
asm.FnL4CsumReplace: false,
asm.FnTailCall: false,
asm.FnCloneRedirect: false,
asm.FnGetCurrentPidTgid: true,
asm.FnGetCurrentUidGid: true,
asm.FnGetCurrentComm: true,
asm.FnGetCgroupClassid: true,
asm.FnSkbVlanPush: false,
asm.FnSkbVlanPop: false,
asm.FnSkbGetTunnelKey: false, // TODO
asm.FnSkbSetTunnelKey: false, // TODO
asm.FnPerfEventRead: true,
asm.FnRedirect: true,
asm.FnGetRouteRealm: true,
asm.FnPerfEventOutput: false,
asm.FnSkbLoadBytes: true,
asm.FnGetStackid: true,
asm.FnCsumDiff: true,
asm.FnSkbGetTunnelOpt: false, // TODO
asm.FnSkbSetTunnelOpt: false, // TODO
asm.FnSkbChangeProto: false,
asm.FnSkbChangeType: false,
asm.FnSkbUnderCgroup: true,
asm.FnGetHashRecalc: true,
asm.FnGetCurrentTask: false, // TODO
asm.FnProbeWriteUser: false, // TODO
asm.FnCurrentTaskUnderCgroup: true,
asm.FnSkbChangeTail: false,
asm.FnSkbPullData: false,
asm.FnCsumUpdate: false,
asm.FnSetHashInvalid: false,
asm.FnGetNumaNodeId: true,
asm.FnSkbChangeHead: false,
asm.FnXdpAdjustHead: false,
asm.FnProbeReadStr: false, // TODO
asm.FnGetSocketCookie: true,
asm.FnGetSocketUid: true,
asm.FnSetHash: false,
asm.FnSetsockopt: false,
asm.FnSkbAdjustRoom: false,
asm.FnRedirectMap: true, // TODO shouldn't we store the redirect info using an emulated func?
asm.FnSkRedirectMap: true, // TODO shouldn't we store the redirect info using an emulated func?
asm.FnSockMapUpdate: false,
asm.FnXdpAdjustMeta: false,
asm.FnPerfEventReadValue: false, // TODO
asm.FnPerfProgReadValue: false, // TODO
asm.FnGetsockopt: false,
asm.FnOverrideReturn: false, // TODO
asm.FnSockOpsCbFlagsSet: false,
asm.FnMsgRedirectMap: true, // TODO shouldn't we store the redirect info using an emulated func?
asm.FnMsgApplyBytes: false, // TODO
asm.FnMsgCorkBytes: false,
asm.FnMsgPullData: false,
asm.FnBind: false, // TODO
asm.FnXdpAdjustTail: false,
asm.FnSkbGetXfrmState: false,
asm.FnGetStack: false, // TODO
asm.FnSkbLoadBytesRelative: true,
asm.FnFibLookup: false, // TODO
asm.FnSockHashUpdate: false,
asm.FnMsgRedirectHash: true, // TODO shouldn't we store the redirect info using an emulated func?
asm.FnSkRedirectHash: true, // TODO shouldn't we store the redirect info using an emulated func?
asm.FnLwtPushEncap: false,
asm.FnLwtSeg6StoreBytes: false,
asm.FnLwtSeg6AdjustSrh: false,
asm.FnLwtSeg6Action: false,
asm.FnRcRepeat: true,
asm.FnRcKeydown: true,
asm.FnSkbCgroupId: true,
asm.FnGetCurrentCgroupId: true,
asm.FnGetLocalStorage: false,
asm.FnSkSelectReuseport: false,
asm.FnSkbAncestorCgroupId: true,
asm.FnSkLookupTcp: false, // TODO
asm.FnSkLookupUdp: false, // TODO
asm.FnSkRelease: false, // TODO
asm.FnMapPushElem: false,
asm.FnMapPopElem: false,
asm.FnMapPeekElem: false,
asm.FnMsgPushData: false,
asm.FnMsgPopData: false,
asm.FnRcPointerRel: true,
asm.FnSpinLock: false,
asm.FnSpinUnlock: false,
asm.FnSkFullsock: false, // TODO
asm.FnTcpSock: false, // TODO
asm.FnSkbEcnSetCe: false, // TODO
asm.FnGetListenerSock: false, // TODO
asm.FnSkcLookupTcp: false, // TODO
asm.FnTcpCheckSyncookie: true,
asm.FnSysctlGetName: false, // TODO
asm.FnSysctlGetCurrentValue: false, // TODO
asm.FnSysctlGetNewValue: false, // TODO
asm.FnSysctlSetNewValue: true,
asm.FnStrtol: true,
asm.FnStrtoul: true,
asm.FnSkStorageGet: false,
asm.FnSkStorageDelete: false,
asm.FnSendSignal: true,
asm.FnTcpGenSyncookie: false,
asm.FnSkbOutput: false,
asm.FnProbeReadUser: false, // TODO
asm.FnProbeReadKernel: false, // TODO
asm.FnProbeReadUserStr: false, // TODO
asm.FnProbeReadKernelStr: false, // TODO
asm.FnTcpSendAck: true,
asm.FnSendSignalThread: true,
asm.FnJiffies64: true,
asm.FnReadBranchRecords: false, // TODO
asm.FnGetNsCurrentPidTgid: false, // TODO
asm.FnXdpOutput: false,
asm.FnGetNetnsCookie: true,
asm.FnGetCurrentAncestorCgroupId: true,
asm.FnSkAssign: true,
asm.FnKtimeGetBootNs: true,
asm.FnSeqPrintf: true,
asm.FnSeqWrite: true,
asm.FnSkCgroupId: true,
asm.FnSkAncestorCgroupId: true,
asm.FnRingbufOutput: false,
asm.FnRingbufReserve: false,
asm.FnRingbufSubmit: false,
asm.FnRingbufDiscard: false,
asm.FnRingbufQuery: false,
asm.FnCsumLevel: false, // TODO
asm.FnSkcToTcp6Sock: false, // TODO
asm.FnSkcToTcpSock: false, // TODO
asm.FnSkcToTcpTimewaitSock: false, // TODO
asm.FnSkcToTcpRequestSock: false, // TODO
asm.FnSkcToUdp6Sock: false, // TODO
asm.FnGetTaskStack: false, // TODO
asm.FnLoadHdrOpt: false, // TODO
asm.FnStoreHdrOpt: true,
asm.FnReserveHdrOpt: true,
asm.FnInodeStorageGet: false,
asm.FnInodeStorageDelete: false,
asm.FnDPath: false, // TODO
asm.FnCopyFromUser: false, // TODO
asm.FnSnprintfBtf: true,
asm.FnSeqPrintfBtf: true,
asm.FnSkbCgroupClassid: true,
asm.FnRedirectNeigh: true,
asm.FnPerCpuPtr: false,
asm.FnThisCpuPtr: false,
asm.FnRedirectPeer: true,
asm.FnTaskStorageGet: false,
asm.FnTaskStorageDelete: false,
asm.FnGetCurrentTaskBtf: false, // TODO
asm.FnBprmOptsSet: true,
asm.FnKtimeGetCoarseNs: true,
asm.FnImaInodeHash: false, // TODO
asm.FnSockFromFile: false, // TODO
asm.FnCheckMtu: true,
asm.FnForEachMapElem: false,
asm.FnSnprintf: false, // TODO
asm.FnSysBpf: true,
asm.FnBtfFindByNameKind: true,
asm.FnSysClose: true,
asm.FnTimerInit: false,
asm.FnTimerSetCallback: false,
asm.FnTimerStart: false,
asm.FnTimerCancel: false,
asm.FnGetFuncIp: true,
asm.FnGetAttachCookie: true,
asm.FnTaskPtRegs: false, // TODO
// bpf_get_branch_snapshot
asm.BuiltinFunc(176): false, // TODO
// bpf_trace_vprintk
asm.BuiltinFunc(177): false, // TODO
// bpf_skc_to_unix_sock
asm.BuiltinFunc(178): false, // TODO
// bpf_kallsyms_lookup_name
asm.BuiltinFunc(179): true,
// bpf_find_vma
asm.BuiltinFunc(180): false,
// bpf_loop
asm.BuiltinFunc(181): false,
// bpf_strncmp
asm.BuiltinFunc(182): true,
// bpf_get_func_arg
asm.BuiltinFunc(183): false, // TODO
// bpf_get_func_ret
asm.BuiltinFunc(184): false, // TODO
// bpf_get_func_arg_cnt
asm.BuiltinFunc(185): true,
// bpf_get_retval
asm.BuiltinFunc(186): true,
// bpf_set_retval
asm.BuiltinFunc(187): true,
}
)
func syscallErr(errNo syscall.Errno) uint64 {
return uint64(int64(0) - int64(errNo))
}
func regToMap(p *Process, reg asm.Register) (LinuxMap, error) {
// Deref the map pointer to get the actual map object
entry, off, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.Get(reg)))
if !found {
return nil, fmt.Errorf("invalid map pointer in %s, can't find entry in memory controller", reg)
}
lm, ok := entry.Object.(LinuxMap)
if !ok {
// There are situations, like when using map-in-map types where we will get a double pointer to a BPF map
// So lets attempts to dereference once more
if vmMem, ok := entry.Object.(VMMem); ok {
addr, err := vmMem.Load(off, asm.Word)
if err != nil {
return nil, fmt.Errorf("Error while attempting to deref dubbel map ptr")
}
entry, _, found = p.VM.MemoryController.GetEntry(uint32(addr))
if !found {
return nil, fmt.Errorf("invalid doubel map pointer in %s, can't find entry in memory controller", reg)
}
lm, ok = entry.Object.(LinuxMap)
if !ok {
return nil, fmt.Errorf("%s doesn't contain pointer or dubbel pointer to a LinuxMap", reg)
}
} else {
return nil, fmt.Errorf("%s doesn't contain pointer to a LinuxMap", reg)
}
}
return lm, nil
}
func derefMapKey(p *Process, register uint64, size uint32) ([]byte, error) {
addr := uint32(register)
// Deref the key to get the actual key value
keyMem, off, found := p.VM.MemoryController.GetEntry(addr)
if !found {
return nil, fmt.Errorf("key unknown to memory controller: 0x%x", addr)
}
vmMem, ok := keyMem.Object.(VMMem)
if !ok {
return nil, fmt.Errorf("key points to non-vm memory: 0x%x", addr)
}
// Read x bytes at the given key pointer, x being the key size indicated by the map spec
keyVal := make([]byte, size)
err := vmMem.Read(off, keyVal)
if err != nil {
return nil, fmt.Errorf("deref key ptr: %w", err)
}
return keyVal, nil
}
func linuxHelperCantEmulate(p *Process) error {
return errors.New("This helper isn't emulated, captured context required")
}
func linuxHelperMapLookupElem(p *Process) error {
// R1 = ptr to the map, R2 = ptr to key
// Deref the map pointer to get the actual map object
lm, err := regToMap(p, asm.R1)
if err != nil {
return err
}
keyVal, err := derefMapKey(p, p.Registers.R2, lm.GetSpec().KeySize)
if err != nil {
return err
}
valPtr, err := lm.Lookup(keyVal, p.CPUID())
if err != nil {
var sysErr syscall.Errno
if !errors.As(err, &sysErr) {
return fmt.Errorf("LinuxMap lookup: %w", err)
}
p.Registers.R0 = uint64(sysErr)
return nil
}
p.Registers.R0 = uint64(valPtr)
return nil
}
func linuxHelperMapUpdateElem(p *Process) error {
// R1 = ptr to the map, R2 = ptr to key, R3 = ptr to value, R4 = flags
// Deref the map pointer to get the actual map object
lm, err := regToMap(p, asm.R1)
if err != nil {
return err
}
lmu, ok := lm.(LinuxMapUpdater)
if !ok {
return fmt.Errorf("given LinuxMap can't be updated")
}
keyVal, err := derefMapKey(p, p.Registers.R2, lm.GetSpec().KeySize)
if err != nil {
return err
}
// Deref the value to get the actual value value
value := uint32(p.Registers.R3)
valMem, off, found := p.VM.MemoryController.GetEntry(value)
if !found {
return fmt.Errorf("value unknown to memory controller: 0x%x", value)
}
vmMem, ok := valMem.Object.(VMMem)
if !ok {
return fmt.Errorf("value points to non-vm memory: 0x%x", value)
}
// Read x bytes at the given value pointer, x being the value size indicated by the map spec
valVal := make([]byte, lm.GetSpec().ValueSize)
err = vmMem.Read(off, valVal)
if err != nil {
return fmt.Errorf("deref value ptr: %w", err)
}
err = lmu.Update(keyVal, valVal, uint32(p.Registers.R4), p.CPUID())
if err != nil {
var sysErr syscall.Errno
if !errors.As(err, &sysErr) {
return fmt.Errorf("LinuxMap update: %w", err)
}
p.Registers.R0 = uint64(sysErr)
return nil
}
p.Registers.R0 = 0
return nil
}
func linuxHelperMapDeleteElem(p *Process) error {
// R1 = ptr to the map, R2 = ptr to key
// Deref the map pointer to get the actual map object
lm, err := regToMap(p, asm.R1)
if err != nil {
return err
}
lmd, ok := lm.(LinuxMapDeleter)
if !ok {
return fmt.Errorf("can't delete from given LinuxMap")
}
keyVal, err := derefMapKey(p, p.Registers.R2, lm.GetSpec().KeySize)
if err != nil {
return err
}
err = lmd.Delete(keyVal)
if err != nil {
var sysErr syscall.Errno
if !errors.As(err, &sysErr) {
return fmt.Errorf("LinuxMap delete: %w", err)
}
p.Registers.R0 = uint64(sysErr)
return nil
}
p.Registers.R0 = 0
return nil
}
func linuxHelperGetKTimeNs(p *Process) error {
// Note: this helper should subtract time the system was suspended, but we don't do that at the moment.
// TODO can we even get access to a suspended-time-counter in userspace? Is this that critical?
bootTime := p.VM.settings.Emulator.(*LinuxEmulator).settings.TimeOfBoot
p.Registers.R0 = uint64(time.Since(bootTime))
return nil
}
// bpf_get_prandom_u32
func linuxHelperGetPRandomU32(p *Process) error {
p.Registers.R0 = uint64(p.VM.settings.Emulator.(*LinuxEmulator).rng.Uint32())
return nil
}
// bpf_get_smp_processor_id
func linuxHelperGetSmpProcessorID(p *Process) error {
p.Registers.R0 = uint64(p.CPUID())
return nil
}
// bpf_skb_store_bytes
func linuxHelperSKBStoreBytes(p *Process) error {
// R1 = ctx (*sk_buff), R2 = offset, R3 = ptr to value, R4 = len, R5 = flags
entry, _, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.R1))
if !found {
return fmt.Errorf("mem ctl, didn't find sk_buff at 0x%08X", p.Registers.R1)
}
buf, ok := entry.Object.(*SKBuff)
if !ok {
return fmt.Errorf("R1 is not a valid sk_buff")
}
// TODO handle flags (BPF_F_RECOMPUTE_CSUM, BPF_F_INVALIDATE_HASH)
entry, off, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.R3))
if !found {
return fmt.Errorf("mem ctl, didn't find vm-mem at 0x%08X", p.Registers.R3)
}
vmmem, ok := entry.Object.(VMMem)
if !ok {
return fmt.Errorf("R3 is not vm-mem")
}
value := make([]byte, p.Registers.R4)
err := vmmem.Read(off, value)
if err != nil {
return fmt.Errorf("vm-mem read: %w", err)
}
err = buf.pkt.Write(uint32(p.Registers.R2), value)
if err != nil {
return fmt.Errorf("pkt write: %w", err)
}
p.Registers.R0 = 0
return nil
}
func linuxHelperTailcall(p *Process) error {
// R1 = ctx, R2 = ptr to the prog array map, R3 = uint32 key
var pastTailcalls int
if i := p.EmulatorValues[LinuxEmuProcValKeyTailcalls]; i != nil {
var ok bool
pastTailcalls, ok = i.(int)
if !ok {
pastTailcalls = 0
}
}
// If we have exceeded the configured max amount of tailcalls, deny execution of another.
// We do this to emulate the behavior of Linux.
if pastTailcalls >= p.VM.settings.Emulator.(*LinuxEmulator).settings.MaxTailCalls {
p.Registers.R0 = syscallErr(syscall.EPERM)
return nil
}
// Deref the map pointer to get the actual map object
lm, err := regToMap(p, asm.R2)
if err != nil {
return err
}
if lm.GetSpec().Type != ebpf.ProgramArray || lm.GetSpec().KeySize != 4 {
return fmt.Errorf("R1 is not a program array map")
}
progArr, ok := lm.(*LinuxArrayMap)
if !ok {
return fmt.Errorf("R1 is not a program array map")
}
// For the tailcall helper the key is passed directly, not as pointer
key := make([]byte, 4)
GetNativeEndianness().PutUint32(key, uint32(p.Registers.R3))
// Lookup should return a pointer into the prog array values
progAddrPtr, err := progArr.Lookup(key, p.CPUID())
if err != nil {
return fmt.Errorf("lookup: %w", err)
}
// Deref the pointer to get the prog array VMMem
entry, off, found := p.VM.MemoryController.GetEntry(progAddrPtr)
if !found {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
vmmem, ok := entry.Object.(VMMem)
if !ok {
return fmt.Errorf("prog array lookup returned pointer to non-vm-memory")
}
// Get the program address from the array
progAddr, err := vmmem.Load(off, asm.Word)
if !ok {
return fmt.Errorf("prog addr lookup: %w", err)
}
// Deref it to get the *ebpf.ProgramSpec
entry, _, found = p.VM.MemoryController.GetEntry(uint32(progAddr))
if !found {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
prog, ok := entry.Object.(*ebpf.ProgramSpec)
if !ok {
// If the address resolves to something other than a program
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
// Change the program
p.Program = prog
// Set the PC to -1, since after returning from the helper the PC is incremented, this will result in a PC of 0
// so the next instruction to be executed is the first of the given program.
p.Registers.PC = -1
// Increment the tailcall count
pastTailcalls++
p.EmulatorValues[LinuxEmuProcValKeyTailcalls] = pastTailcalls
return nil
}
const (
// Mask containing the desired CPU index
bpfFIndexMask = 0xffffffff
// If masked flags is equal to bpfFCurrentCPU, use the current CPU as index
bpfFCurrentCPU = bpfFIndexMask
// Mask used to communicate the length of the ctx, for use in bpf_xdp_event_output and bpf_skb_event_output
// bpfFCtxLenMask = 0xfffff << 32
)
func linuxHelperEventOutput(p *Process) error {
// R1 = ctx, R2 = ptr to the perf array map, R3 = uint64 flags, R4 = ptr to value, R5 = uint64 size
// Deref the map pointer to get the actual map object
lm, err := regToMap(p, asm.R2)
if err != nil {
return err
}
m, ok := lm.(*LinuxPerfEventArrayMap)
if !ok {
return fmt.Errorf("R1 is not a perf event array map")
}
entry, off, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.R4))
if !found {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
vmmem, ok := entry.Object.(VMMem)
if !ok {
return fmt.Errorf("prog array lookup returned pointer to non-vm-memory")
}
val := make([]byte, p.Registers.R5)
err = vmmem.Read(off, val)
if err != nil {
return fmt.Errorf("vmmem read: %w", err)
}
idx := p.Registers.R3 & bpfFIndexMask
if idx == bpfFCurrentCPU {
idx = uint64(p.CPUID())
}
if int(idx) < 0 {
return fmt.Errorf("invalid cpuid: %d", idx)
}
err = m.Push(val, int(idx))
if err != nil {
if syserr, ok := err.(syscall.Errno); ok {
p.Registers.R0 = syscallErr(syserr)
return nil
}
return fmt.Errorf("push: %w", err)
}
return nil
}
// bpf_skb_change_tail
func linuxHelperSkbChangeTail(p *Process) error {
// R1 = ctx (*sk_buff), R2 = delta
entry, _, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.R1))
if !found {
return fmt.Errorf("mem ctl, didn't find sk_buff at 0x%08X", p.Registers.R1)
}
buf, ok := entry.Object.(*SKBuff)
if !ok {
return fmt.Errorf("R1 is not a valid sk_buff")
}
delta := int32(p.Registers.R2)
org := delta
if delta >= 0 {
avail := buf.tail - buf.end
if delta > int32(avail) {
delta = int32(avail)
}
} else {
avail := buf.end - buf.data
if delta < int32(avail) {
delta = int32(avail)
}
}
buf.end = uint32(int32(buf.tail) + delta)
buf.computeDataPointers()
if org == delta {
p.Registers.R0 = 0
} else {
p.Registers.R0 = syscallErr(1)
}
return nil
}
func linuxHelperXDPAdjustTail(p *Process) error {
delta := int64(p.Registers.R2)
// R1 = ptr to ctx, R2 = delta
entry, _, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.R1))
if !found {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
xdpmd, ok := entry.Object.(*PlainMemory)
if !ok {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
// The XDP_MD ctx is 20 bytes, this is a sanity check
if len(xdpmd.Backing) != 20 {
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
dataAddr, err := xdpmd.Load(0, asm.Word)
if err != nil {
return err
}
dataEndAddr, err := xdpmd.Load(4, asm.Word)
if err != nil {
return err
}
entry, offset, found := p.VM.MemoryController.GetEntry(uint32(dataEndAddr))
if !found {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
pkt, ok := entry.Object.(*PlainMemory)
if !ok {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
curSize := dataEndAddr - dataAddr
availableTailroom := len(pkt.Backing) - int(offset)
if delta >= 0 {
// If the users wants to grow beyond the available tailroom
if delta > int64(availableTailroom) {
p.Registers.R0 = syscallErr(syscall.E2BIG)
return nil
}
} else {
// If the user wants to shrink beyond start of packet
if -delta >= int64(curSize) {
p.Registers.R0 = syscallErr(syscall.E2BIG)
return nil
}
}
newDataEndAddr := int64(dataEndAddr) + delta
err = xdpmd.Store(4, uint64(newDataEndAddr), asm.Word)
if err != nil {
return fmt.Errorf("update data end: %w", err)
}
return nil
}
func linuxHelperMapPushElem(p *Process) error {
// R1 = ptr to map, R2 = ptr to value, R3 = flags
// Deref the map pointer to get the actual map object
lm, err := regToMap(p, asm.R1)
if err != nil {
return err
}
pm, ok := lm.(LinuxMapPusher)
if !ok {
return fmt.Errorf("given map is not a LinuxMapPusher")
}
entry, off, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.R2))
if !found {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
vmmem, ok := entry.Object.(VMMem)
if !ok {
return fmt.Errorf("value is pointer to non-vm-memory")
}
val := make([]byte, lm.GetSpec().ValueSize)
err = vmmem.Read(off, val)
if err != nil {
return fmt.Errorf("vmmem read: %w", err)
}
err = pm.Push(val, p.CPUID())
if err != nil {
if syserr, ok := err.(syscall.Errno); ok {
p.Registers.R0 = syscallErr(syserr)
return nil
}
return fmt.Errorf("push: %w", err)
}
p.Registers.R0 = 0
return nil
}
func linuxHelperMapPopElem(p *Process) error {
// R1 = ptr to map, R2 = ptr to value
// Deref the map pointer to get the actual map object
lm, err := regToMap(p, asm.R1)
if err != nil {
return err
}
pm, ok := lm.(LinuxMapPopper)
if !ok {
return fmt.Errorf("given map is not a LinuxMapPopper")
}
entry, off, found := p.VM.MemoryController.GetEntry(uint32(p.Registers.R2))
if !found {
// If the address is not valid, handle it gracefully
p.Registers.R0 = syscallErr(syscall.EINVAL)
return nil
}
vmmem, ok := entry.Object.(VMMem)
if !ok {
return fmt.Errorf("value is pointer to non-vm-memory")
}
val, err := pm.Pop(p.CPUID())
if err != nil {
if syserr, ok := err.(syscall.Errno); ok {
p.Registers.R0 = syscallErr(syserr)
return nil
}
return fmt.Errorf("pop: %w", err)
}
// Map empty
if val == 0 {
p.Registers.R0 = syscallErr(syscall.ENOMSG)
return nil
}