Commit 031acd8c authored by Jason Wessel's avatar Jason Wessel
Browse files

x86,kgdb: Implement early hardware breakpoint debugging 



It is not possible to use the hw_breakpoint.c API prior to mm_init(),
but it is possible to use hardware breakpoints with the kernel
debugger.

Prior to smp_init() it is possible to simply write to the dr registers
of the boot cpu directly.  This can be used up until the
kgdb_arch_late() is invoked, at which point the standard hw_breakpoint.c
API will get used.

CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarJason Wessel <jason.wessel@windriver.com>
parent 0b4b3827

arch/x86/kernel/kgdb.c

+28 −2
Original line number Diff line number Diff line
@@ -199,6 +199,8 @@ static struct hw_breakpoint { 
	struct perf_event	**pev;

} breakinfo[4];



static unsigned long early_dr7;



static void kgdb_correct_hw_break(void)

{

	int breakno;
@@ -210,6 +212,14 @@ static void kgdb_correct_hw_break(void) 
		int cpu = raw_smp_processor_id();

		if (!breakinfo[breakno].enabled)

			continue;

		if (dbg_is_early) {

			set_debugreg(breakinfo[breakno].addr, breakno);

			early_dr7 |= encode_dr7(breakno,

						breakinfo[breakno].len,

						breakinfo[breakno].type);

			set_debugreg(early_dr7, 7);

			continue;

		}

		bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);

		info = counter_arch_bp(bp);

		if (bp->attr.disabled != 1)
@@ -224,6 +234,7 @@ static void kgdb_correct_hw_break(void) 
		if (!val)

			bp->attr.disabled = 0;

	}

	if (!dbg_is_early)

		hw_breakpoint_restore();

}
@@ -233,6 +244,9 @@ static int hw_break_reserve_slot(int breakno) 
	int cnt = 0;

	struct perf_event **pevent;



	if (dbg_is_early)

		return 0;



	for_each_online_cpu(cpu) {

		cnt++;

		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
@@ -258,6 +272,9 @@ static int hw_break_release_slot(int breakno) 
	struct perf_event **pevent;

	int cpu;



	if (dbg_is_early)

		return 0;



	for_each_online_cpu(cpu) {

		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);

		if (dbg_release_bp_slot(*pevent))
@@ -302,6 +319,10 @@ static void kgdb_remove_all_hw_break(void) 
		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);

		if (bp->attr.disabled == 1)

			continue;

		if (dbg_is_early)

			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,

						 breakinfo[i].type);

		else

			arch_uninstall_hw_breakpoint(bp);

		bp->attr.disabled = 1;

	}
@@ -379,6 +400,11 @@ void kgdb_disable_hw_debug(struct pt_regs *regs) 
	for (i = 0; i < 4; i++) {

		if (!breakinfo[i].enabled)

			continue;

		if (dbg_is_early) {

			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,

						 breakinfo[i].type);

			continue;

		}

		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);

		if (bp->attr.disabled == 1)

			continue;

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