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SubjectRe: [PATCH 1/4] x86,hw_breakpoint,kgdb: kgdb to use hw_breakpointAPI
New version which loses the call back registration, because if we
register as a different breakpoint type, perf won't reject it. I didn't
see that loop hole in the API the first time around.

Also the dr7 fixup in hw_breakpoint.c is not needed.

The trickery for entering twice into the __kgdb_notify is gone too.

All the regression tests are still passing.

---
arch/x86/kernel/kgdb.c | 173
++++++++++++++++++++++++++++++++-----------------
kernel/kgdb.c | 3
2 files changed, 118 insertions(+), 58 deletions(-)
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -42,6 +42,7 @@
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/nmi.h>
+#include <linux/hw_breakpoint.h>

#include <asm/debugreg.h>
#include <asm/apicdef.h>
@@ -204,40 +205,38 @@ void gdb_regs_to_pt_regs(unsigned long *

static struct hw_breakpoint {
unsigned enabled;
- unsigned type;
- unsigned len;
unsigned long addr;
+ int len;
+ int type;
+ struct perf_event **pev;
} breakinfo[4];

static void kgdb_correct_hw_break(void)
{
- unsigned long dr7;
- int correctit = 0;
- int breakbit;
int breakno;

- get_debugreg(dr7, 7);
for (breakno = 0; breakno < 4; breakno++) {
- breakbit = 2 << (breakno << 1);
- if (!(dr7 & breakbit) && breakinfo[breakno].enabled) {
- correctit = 1;
- dr7 |= breakbit;
- dr7 &= ~(0xf0000 << (breakno << 2));
- dr7 |= ((breakinfo[breakno].len << 2) |
- breakinfo[breakno].type) <<
- ((breakno << 2) + 16);
- set_debugreg(breakinfo[breakno].addr, breakno);
-
- } else {
- if ((dr7 & breakbit) && !breakinfo[breakno].enabled) {
- correctit = 1;
- dr7 &= ~breakbit;
- dr7 &= ~(0xf0000 << (breakno << 2));
- }
- }
+ struct perf_event *bp;
+ struct arch_hw_breakpoint *info;
+ int val;
+ int cpu = raw_smp_processor_id();
+ if (!breakinfo[breakno].enabled)
+ continue;
+ bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
+ info = counter_arch_bp(bp);
+ if (bp->attr.disabled != 1)
+ continue;
+ bp->attr.bp_addr = breakinfo[breakno].addr;
+ bp->attr.bp_len = breakinfo[breakno].len;
+ bp->attr.bp_type = breakinfo[breakno].type;
+ info->address = breakinfo[breakno].addr;
+ info->len = breakinfo[breakno].len;
+ info->type = breakinfo[breakno].type;
+ val = arch_install_hw_breakpoint(bp);
+ if (!val)
+ bp->attr.disabled = 0;
}
- if (correctit)
- set_debugreg(dr7, 7);
+ hw_breakpoint_restore();
}

static int
@@ -259,15 +258,23 @@ kgdb_remove_hw_break(unsigned long addr,
static void kgdb_remove_all_hw_break(void)
{
int i;
+ int cpu = raw_smp_processor_id();
+ struct perf_event *bp;

- for (i = 0; i < 4; i++)
- memset(&breakinfo[i], 0, sizeof(struct hw_breakpoint));
+ for (i = 0; i < 4; i++) {
+ if (!breakinfo[i].enabled)
+ continue;
+ bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
+ if (bp->attr.disabled == 1)
+ continue;
+ arch_uninstall_hw_breakpoint(bp);
+ bp->attr.disabled = 1;
+ }
}

static int
kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
{
- unsigned type;
int i;

for (i = 0; i < 4; i++)
@@ -278,27 +285,38 @@ kgdb_set_hw_break(unsigned long addr, in

switch (bptype) {
case BP_HARDWARE_BREAKPOINT:
- type = 0;
- len = 1;
+ len = 1;
+ breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
break;
case BP_WRITE_WATCHPOINT:
- type = 1;
+ breakinfo[i].type = X86_BREAKPOINT_WRITE;
break;
case BP_ACCESS_WATCHPOINT:
- type = 3;
+ breakinfo[i].type = X86_BREAKPOINT_RW;
break;
default:
return -1;
}
-
- if (len == 1 || len == 2 || len == 4)
- breakinfo[i].len = len - 1;
- else
- return -1;
-
- breakinfo[i].enabled = 1;
+ switch (len) {
+ case 1:
+ breakinfo[i].len = X86_BREAKPOINT_LEN_1;
+ break;
+ case 2:
+ breakinfo[i].len = X86_BREAKPOINT_LEN_2;
+ break;
+ case 4:
+ breakinfo[i].len = X86_BREAKPOINT_LEN_4;
+ break;
+#ifdef CONFIG_X86_64
+ case 8:
+ breakinfo[i].len = X86_BREAKPOINT_LEN_8;
+ break;
+#endif
+ default:
+ return -1;
+ }
breakinfo[i].addr = addr;
- breakinfo[i].type = type;
+ breakinfo[i].enabled = 1;

return 0;
}
@@ -313,8 +331,21 @@ kgdb_set_hw_break(unsigned long addr, in
*/
void kgdb_disable_hw_debug(struct pt_regs *regs)
{
+ int i;
+ int cpu = raw_smp_processor_id();
+ struct perf_event *bp;
+
/* Disable hardware debugging while we are in kgdb: */
set_debugreg(0UL, 7);
+ for (i = 0; i < 4; i++) {
+ if (!breakinfo[i].enabled)
+ continue;
+ bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
+ if (bp->attr.disabled == 1)
+ continue;
+ arch_uninstall_hw_breakpoint(bp);
+ bp->attr.disabled = 1;
+ }
}

/**
@@ -378,7 +409,6 @@ int kgdb_arch_handle_exception(int e_vec
struct pt_regs *linux_regs)
{
unsigned long addr;
- unsigned long dr6;
char *ptr;
int newPC;

@@ -404,20 +434,6 @@ int kgdb_arch_handle_exception(int e_vec
raw_smp_processor_id());
}

- get_debugreg(dr6, 6);
- if (!(dr6 & 0x4000)) {
- int breakno;
-
- for (breakno = 0; breakno < 4; breakno++) {
- if (dr6 & (1 << breakno) &&
- breakinfo[breakno].type == 0) {
- /* Set restore flag: */
- linux_regs->flags |= X86_EFLAGS_RF;
- break;
- }
- }
- }
- set_debugreg(0UL, 6);
kgdb_correct_hw_break();

return 0;
@@ -485,8 +501,7 @@ static int __kgdb_notify(struct die_args
break;

case DIE_DEBUG:
- if (atomic_read(&kgdb_cpu_doing_single_step) ==
- raw_smp_processor_id()) {
+ if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
if (user_mode(regs))
return single_step_cont(regs, args);
break;
@@ -539,7 +554,42 @@ static struct notifier_block kgdb_notifi
*/
int kgdb_arch_init(void)
{
- return register_die_notifier(&kgdb_notifier);
+ int i, cpu;
+ int ret;
+ struct perf_event_attr attr;
+ struct perf_event **pevent;
+
+ ret = register_die_notifier(&kgdb_notifier);
+ if (ret != 0)
+ return ret;
+ /*
+ * Pre-allocate the hw breakpoint structions in the non-atomic
+ * portion of kgdb because this operation requires mutexs to
+ * complete.
+ */
+ attr.bp_addr = (unsigned long)kgdb_arch_init;
+ attr.type = PERF_TYPE_BREAKPOINT;
+ attr.bp_len = HW_BREAKPOINT_LEN_1;
+ attr.bp_type = HW_BREAKPOINT_W;
+ attr.disabled = 1;
+ for (i = 0; i < 4; i++) {
+ breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL);
+ if (IS_ERR(breakinfo[i].pev)) {
+ printk(KERN_ERR "kgdb: Could not allocate hw breakpoints\n");
+ breakinfo[i].pev = NULL;
+ kgdb_arch_exit();
+ return -1;
+ }
+ for_each_online_cpu(cpu) {
+ pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
+ pevent[0]->hw.sample_period = 1;
+ if (pevent[0]->destroy != NULL) {
+ pevent[0]->destroy = NULL;
+ release_bp_slot(*pevent);
+ }
+ }
+ }
+ return ret;
}

/**
@@ -550,6 +600,13 @@ int kgdb_arch_init(void)
*/
void kgdb_arch_exit(void)
{
+ int i;
+ for (i = 0; i < 4; i++) {
+ if (breakinfo[i].pev) {
+ unregister_wide_hw_breakpoint(breakinfo[i].pev);
+ breakinfo[i].pev = NULL;
+ }
+ }
unregister_die_notifier(&kgdb_notifier);
}

--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -578,6 +578,9 @@ static void kgdb_wait(struct pt_regs *re
smp_wmb();
atomic_set(&cpu_in_kgdb[cpu], 1);

+ /* Disable any cpu specific hw breakpoints */
+ kgdb_disable_hw_debug(regs);
+
/* Wait till primary CPU is done with debugging */
while (atomic_read(&passive_cpu_wait[cpu]))
cpu_relax();


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