BT - Set Time-stamped Breakpoint Trace

Set a time-stamped breakpoint trace.

Syntax:

──┬─ BT  ─┬─ addr ────────────────────────────────────────────
    └─ BTn ─┘

Parameters:

n

Explicitly specifies a breakpoint number to be assigned to this breakpoint. A value from 0 to 9 may be specified. If specified, there must be no space between the number and the BT command.

The default is to assign the lowest available number. If all 10 breakpoint numbers have been assigned then the following message appears:

Too many breakpoints

addr
The address of the breakpoint.

The Kernel Debugger saves the byte of storage at the location specified by addr and inserts an INT 3 instruction in its place.

Notes

Whenever the Kernel Debugger is entered the storage overlayed by any breakpoints is temporarily restored. When the Kernel Debugger gives control back to the system, enabled breakpoints are re-instated.

If addr specifies the address of an existing breakpoint then the existing breakpoint is updated with the new parameters.

Results & Notes:

If the address is valid then the breakpoint definition is accepted and enabled. When enabled, the time-stamp breakpoint causes the current high resolution system time to be saved in a time-stamp circular trace buffer whenever the breakpoint address is executed.

The trace buffer will record up to 4K entries before wrapping.

Unlike the BP and BR commands, BT does not return control to user when the breakpoint is encountered.

The time-stamp trace may be displayed using the BS command.

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