KernBlock

This is an extended version of the DevHlp_ProcBlock function. Basically, you specify an arbitrary eventid and a timeout. The block may be coordinated with either an acquired spinlock or a mutexlock, as declared by the flags. The lock is released immediately before blocking, and reacquired after returning from the routine, unless the flag bit KEE_BLOCK_NOACQUIRE prevents re-acquiration. The blocked thread will hang in this routine, and can be resurrected by a signal (unless turned off with KEE_BLOCK_NOSIGNALS) or a KernWakeup with the same eventid.

Synopsis

APIRET APIENTRY KernBlock(ULONG eventid, ULONG timeout, ULONG flags, PVOID lockptr, PULONG retdata);

Parameters

eventid (ULONG) - input

Some unique value, which is to be used by KernWakeup to unblock the thread again.

timeout (ULONG) - input

a timeout value in milliseconds. 0xffffffff is supposedly infinite wait.

flags (ULONG) - input

One or more of the following flags:

KEE_BLOCK_NOSIGNALS - Ignore signals, i.e. the block can be released only by end of timeout or an explicit wakeup.

KEE_BLOCK_SPINLOCK - The lockptr points to an acquired KEESpinLock structure.

KEE_BLOCK_EXMUTEXLOCK - The lockptr points to an acquired exclusive mutexlock structure.

KEE_BLOCK_SHMUTEXLOCK - The lockptr points to an acquired shared mutexlock structure.

KEE_BLOCK_NOACQUIRE - Don't reacquire the lock (if lockptr points to a lock at all) when the KernBlock routine returns.

lockptr (PVOID) - input

Used when one of the three *LOCK bits is set: points to the specified lock structure

retdata (PULONG) - input

points to a long variable that receives the value passed by the KernWakeup routine. May be NULL, in this case the value is ignored.

Comments

The KEE_NOSIGNALS bit looks dangerous to me - you can this way easily produce unkillable processes: Block in an ioctl with this bit set, and a bug preventing the wakeup, and you won't get rid of this process anymore. The three *LOCK bits are exclusive since there is only one pointer. I guess the retdata value is irrelevant for a timeout or an interrupt by a signal (return values ERROR_TIMEOUT or ERROR_INTERRUPT).