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Writing Device Drivers
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dump() and print() Entry Points

This section discusses the dump(9E) and print(9E) entry points.

dump() Entry Point (Block Drivers)

The dump(9E) entry point is used to copy a portion of virtual address space directly to the specified device in the case of a system failure. dump() is also used to copy the state of the kernel out to disk during a checkpoint operation. See the cpr(7) and dump(9E) man pages for more information. The entry point must be capable of performing this operation without the use of interrupts, because interrupts are disabled during the checkpoint operation.

int dump(dev_t dev, caddr_t addr, daddr_t blkno, int nblk)



Device number of the device to receive the dump.


Base kernel virtual address at which to start the dump.


Block at which the dump is to start.


Number of blocks to dump.

The dump depends upon the existing driver working properly.

print() Entry Point (Block Drivers)

int print(dev_t dev, char *str)

The print(9E) entry point is called by the system to display a message about an exception that has been detected. print(9E) should call cmn_err(9F) to post the message to the console on behalf of the system. The following example demonstrates a typical print() entry point.

static int
 xxprint(dev_t dev, char *str)
     cmn_err(CE_CONT, “xx: %s\n”, str);
     return (0);
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  Published under the terms fo the Public Documentation License Version 1.01. Design by Interspire