About KDB global and local hardware breakpoint support in IA3 2.

[Zhang, Sonic]

Hi,

	I am sorry, I didn't explain it very clearly.

	In current implementation for i386, a table for hardware breakpoints
is defined as follows:

	kdbhard_bp_t	kdb_hardbreaks[KDB_MAXHARDBPT];

	This means all CPUs share the same data structure of hardware
breakpoints. For example, the breakpoint in DR0 of each CPU refers to
kdb_hardbreaks[0], DR1 refers to kdb_hardbreaks[1], etc. The
kdb_hardbreaks[0] is installed to each CPU, when the CPU leaves KDB. Then,
all hardware breakpoints are global. And you can not create a local one for
one CPU and a different local one for the other CPU. So I change this data
structure into:
	kdbhard_bp_t	kdb_hardbreaks[KDB_MAXHARDBPT][NR_CPUS];


	In addition, each CPU executes kdb_bp_install_local() and
kdb_bp_remove_local() in kdb(), while only the initial CPU executes
kdb_bp_install_global() and kdb_bp_remove_global(). That means only the
initial CPU can install and remove a global breakpoint. But a hardware
global breakpoint must be installed and removed by each CPU itself. So, I
guess that you consider the global breakpoint the same as a instruction
breakpoint. Don't you think it doesn't accord with the definition of KDB
commands "bpa" and "bpha".  That's why I rename the string "local" with
"dbreg" and "global" with "inst".

	Thanks.

	Regards.

	Sonic Zhang


-----Original Message-----
From: Keith Owens [mailto:kaos at sgi.com]
Sent: 2003?2?13? 18:02
To: Zhang, Sonic
Cc: KDB (E-mail)
Subject: Re: About KDB global and local hardware breakpoint support in IA32.



On Thu, 13 Feb 2003 15:59:45 +0800, 
"Zhang, Sonic" <sonic.zhang at intel.com> wrote:
>	Current implementation in kdb-v3.0-2.4.20 sees a local breakpoint as
>an equivalence of a global breakpoint. All CPUs share the same data
>structure for hardware debug registers. And each CPU sets its debug
register
>for a hardware breakpoint, no matter whether it is a local one of the other
>CPUs.

Where do you get that from?  kdb_bp_install_local() is

void
kdb_bp_install_local(struct pt_regs *regs)
{
	int i;

	for(i=0; i<KDB_MAXBPT; i++) {
		if (KDB_DEBUG(BP)) {
			kdb_printf("kdb_bp_install_local bp %d bp_enabled %d
bp_global %d cpu %d bp_cpu %d\n",
				i, kdb_breakpoints[i].bp_enabled,
kdb_breakpoints[i].bp_global,
				smp_processor_id(),
kdb_breakpoints[i].bp_cpu);
		}
		if (kdb_breakpoints[i].bp_enabled
		 && kdb_breakpoints[i].bp_cpu == smp_processor_id()
		 && !kdb_breakpoints[i].bp_global){
			kdba_installbp(regs, &kdb_breakpoints[i]);
		}
	}
}

That function is called for each cpu as it leaves kdb.  It only
installs local breakpoints for the current cpu.

kdb_bp() has
	if (hardware && !global) {
		bp->bp_global = 0;
		bp->bp_cpu = smp_processor_id();
	}
marking local breakpoints by their cpu number.