KernBlock: Difference between revisions
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==Parameters== | ==Parameters== | ||
; eventid : Some unique value, which is to be used by KernWakeup to unblock the thread again. | ;eventid: Some unique value, which is to be used by KernWakeup to unblock the thread again. | ||
;timeout: a timeout value in milliseconds. 0xffffffff is supposedly infinite wait. | |||
; timeout : a timeout value in milliseconds. 0xffffffff is supposedly infinite wait. | ;flags: 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. | |||
; flags : One or more of the following flags: | ::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: Used when one of the three *LOCK bits is set: points to the specified lock structure | |||
;retdata: points to a long variable that receives the value passed by the KernWakeup routine. May be NULL, in this case the value is ignored. | |||
; lockptr : Used when one of the three *LOCK bits is set: points to the specified lock structure | |||
; retdata : 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== | ==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. | 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 us irrelevant for a timeout or an interrupt by a signal (return values ERROR_TIMEOUT and ERROR_INTERRUPT). | I guess the retdata value us irrelevant for a timeout or an interrupt by a signal (return values ERROR_TIMEOUT and ERROR_INTERRUPT). | ||
[[Category:KEE]] | [[Category:KEE]] | ||
Revision as of 12:21, 19 July 2020
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
- Some unique value, which is to be used by KernWakeup to unblock the thread again.
- timeout
- a timeout value in milliseconds. 0xffffffff is supposedly infinite wait.
- flags
- 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
- Used when one of the three *LOCK bits is set: points to the specified lock structure
- retdata
- 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 us irrelevant for a timeout or an interrupt by a signal (return values ERROR_TIMEOUT and ERROR_INTERRUPT).