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x86,kgdb: Implement early hardware breakpoint debugging

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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: Jason Wessel <jason.wessel@windriver.com>
This commit is contained in:
Jason Wessel
2010-05-20 21:04:30 -05:00
parent 0b4b3827db
commit 031acd8c42
1 changed files with 28 additions and 2 deletions
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30
arch/x86/kernel/kgdb.c
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@@ -199,6 +199,8 @@ static struct hw_breakpoint {
struct perf_event **pev; struct perf_event **pev;
} breakinfo[4]; } breakinfo[4];
static unsigned long early_dr7;
static void kgdb_correct_hw_break(void) static void kgdb_correct_hw_break(void)
{ {
int breakno; int breakno;
@@ -210,6 +212,14 @@ static void kgdb_correct_hw_break(void)
int cpu = raw_smp_processor_id(); int cpu = raw_smp_processor_id();
if (!breakinfo[breakno].enabled) if (!breakinfo[breakno].enabled)
continue; 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); bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
info = counter_arch_bp(bp); info = counter_arch_bp(bp);
if (bp->attr.disabled != 1) if (bp->attr.disabled != 1)
@@ -224,7 +234,8 @@ static void kgdb_correct_hw_break(void)
if (!val) if (!val)
bp->attr.disabled = 0; bp->attr.disabled = 0;
} }
hw_breakpoint_restore(); if (!dbg_is_early)
hw_breakpoint_restore();
} }
static int hw_break_reserve_slot(int breakno) static int hw_break_reserve_slot(int breakno)
@@ -233,6 +244,9 @@ static int hw_break_reserve_slot(int breakno)
int cnt = 0; int cnt = 0;
struct perf_event **pevent; struct perf_event **pevent;
if (dbg_is_early)
return 0;
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
cnt++; cnt++;
pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu); pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
@@ -258,6 +272,9 @@ static int hw_break_release_slot(int breakno)
struct perf_event **pevent; struct perf_event **pevent;
int cpu; int cpu;
if (dbg_is_early)
return 0;
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu); pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
if (dbg_release_bp_slot(*pevent)) if (dbg_release_bp_slot(*pevent))
@@ -302,7 +319,11 @@ static void kgdb_remove_all_hw_break(void)
bp = *per_cpu_ptr(breakinfo[i].pev, cpu); bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
if (bp->attr.disabled == 1) if (bp->attr.disabled == 1)
continue; continue;
arch_uninstall_hw_breakpoint(bp); 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; bp->attr.disabled = 1;
} }
} }
@@ -379,6 +400,11 @@ void kgdb_disable_hw_debug(struct pt_regs *regs)
for (i = 0; i < 4; i++) { for (i = 0; i < 4; i++) {
if (!breakinfo[i].enabled) if (!breakinfo[i].enabled)
continue; 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); bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
if (bp->attr.disabled == 1) if (bp->attr.disabled == 1)
continue; continue;