> > >> Then how do they implement memory watch? >> > > Got me, but even the ancient, in-tree gdb is able to do so. Have you > consulted the gdb source? >
I read gdb sources and found an asnwer, but later I read docs and here it is: https://sourceware.org/gdb/onlinedocs/gdb/Set-Watchpoints.html "Depending on your system, watchpoints may be implemented in software or hardware. GDB does software watchpointing by single-stepping your program and testing the variable’s value each time, which is hundreds of times slower than normal execution. " For bsd, configure script checks GETDBREGS in ptrace.h. It exists in freebsd but not in openbsd. Then, "target_can_use_hardware_watchpoint" returns 0, and "breakpoint.c" checks it, and switches to software watchpoints. Same happens when debug registers are full even on linux, I assume.
