Injecting Faults

The test harness operates at the level of data accesses. A data access has the following characteristics:

• Type of hardware being accessed (driver name)

• Instance of the hardware being accessed (driver instance)

• Register set being tested

• Subset of the register set that is targeted

• Direction of the transfer (read or write)

• Type of access (PIO or DMA)

The test harness intercepts data accesses and injects appropriate faults into the driver. An errdef, specified by the th_define(1M) command, encodes the following information:

• The driver instance and register set being tested (-n name, -i instance, and -r reg_number).

• The subset of the register set eligible for corruption. This subset is indicated by providing an offset into the register set and a length from that offset (-l offset [len]).

• The kind of access to be intercepted: log, pio, dma, pio_r, pio_w, dma_r, dma_w, intr (-a acc_types).

• How many accesses should be faulted (-c count [failcount]).

• The kind of corruption that should be applied to a qualifying access (-o operator [operand]).

  • Replace datum with a fixed value (EQUAL)

  • Perform a bitwise operation on the datum (AND, OR, XOR)

  • Ignore the transfer (for host to I/O accesses NO_TRANSFER)

  • Lose, delay, or inject spurious interrupts (LOSE, DELAY, EXTRA)

Use the -a acc_chk option to simulate framework faults in an errdef.