Remove all hardware watchpoints in Linux kernel 3.0.0

Question

After setting the first (and only possible) hardware watchpoint via watch varname in GDB, it's not possible to remove it via delete.

Even if I just exit GDB, this watchpoint seems to be enabled till the next reboot. When I try to set another hardware watchpoint after GDB is restarted, a kernel message appears in logs telling me, all hardware watchpoints are already taken. It seems like it's the same problem as in Setting GDB hardware watchpoint/how to set software watchpoint, but because I need a hardware watchpoint, the solution does not apply.

Is there a tool or a syscall to remove this (or all) hardware watchpoint? The CPU is an Core i5 and the Linux kernel is 3.0.0-17-generic from Ubuntu 11.10 (Oneiric Ocelot).

Answer 1

Use watchpoints (sometimes called data breakpoints). It can handle it as normal breakpoints, as follows:

(gdb) info watchpoints
Num     Type           Disp Enb Address            What
2       acc watchpoint keep y                      x

(gdb) delete 2

(gdb) info watchpoints
No watchpoints.
(gdb)

A good reference is Setting Watchpoints.