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hw-breakpoints: Use overflow handler instead of the event callback

Browse source 
struct perf_event::event callback was called when a breakpoint
triggers. But this is a rather opaque callback, pretty
tied-only to the breakpoint API and not really integrated into perf
as it triggers even when we don't overflow.

We prefer to use overflow_handler() as it fits into the perf events
rules, being called only when we overflow.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>
This commit is contained in:
Frederic Weisbecker 2009-12-05 09:44:31 +01:00
parent 2f0993e0fb
commit b326e9560a
8 changed files with 48 additions and 57 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
arch/x86/kernel/hw_breakpoint.c
View file

@ -362,8 +362,7 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp,
return ret;
}
if (bp->callback)
ret = arch_store_info(bp);
ret = arch_store_info(bp);
if (ret < 0)
return ret;
@ -519,7 +518,7 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args)
break;
}
(bp->callback)(bp, args->regs);
perf_bp_event(bp, args->regs);
rcu_read_unlock();
}

9
arch/x86/kernel/ptrace.c
View file

@ -555,7 +555,9 @@ static int genregs_set(struct task_struct *target,
return ret;
}
static void ptrace_triggered(struct perf_event *bp, void *data)
static void ptrace_triggered(struct perf_event *bp, int nmi,
struct perf_sample_data *data,
struct pt_regs *regs)
{
int i;
struct thread_struct *thread = &(current->thread);
@ -599,7 +601,7 @@ ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
{
int err;
int gen_len, gen_type;
DEFINE_BREAKPOINT_ATTR(attr);
struct perf_event_attr attr;
/*
* We shoud have at least an inactive breakpoint at this
@ -721,9 +723,10 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
{
struct perf_event *bp;
struct thread_struct *t = &tsk->thread;
DEFINE_BREAKPOINT_ATTR(attr);
struct perf_event_attr attr;
if (!t->ptrace_bps[nr]) {
hw_breakpoint_init(&attr);
/*
* Put stub len and type to register (reserve) an inactive but
* correct bp

25
include/linux/hw_breakpoint.h
View file

@ -20,19 +20,16 @@ enum {
#ifdef CONFIG_HAVE_HW_BREAKPOINT
/* As it's for in-kernel or ptrace use, we want it to be pinned */
#define DEFINE_BREAKPOINT_ATTR(name) \
struct perf_event_attr name = { \
.type = PERF_TYPE_BREAKPOINT, \
.size = sizeof(name), \
.pinned = 1, \
};
static inline void hw_breakpoint_init(struct perf_event_attr *attr)
{
attr->type = PERF_TYPE_BREAKPOINT;
attr->size = sizeof(*attr);
/*
* As it's for in-kernel or ptrace use, we want it to be pinned
* and to call its callback every hits.
*/
attr->pinned = 1;
attr->sample_period = 1;
}
static inline unsigned long hw_breakpoint_addr(struct perf_event *bp)
@ -52,7 +49,7 @@ static inline int hw_breakpoint_len(struct perf_event *bp)
extern struct perf_event *
register_user_hw_breakpoint(struct perf_event_attr *attr,
perf_callback_t triggered,
perf_overflow_handler_t triggered,
struct task_struct *tsk);
/* FIXME: only change from the attr, and don't unregister */
@ -64,12 +61,12 @@ modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr);
*/
extern struct perf_event *
register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
perf_callback_t triggered,
perf_overflow_handler_t triggered,
int cpu);
extern struct perf_event **
register_wide_hw_breakpoint(struct perf_event_attr *attr,
perf_callback_t triggered);
perf_overflow_handler_t triggered);
extern int register_perf_hw_breakpoint(struct perf_event *bp);
extern int __register_perf_hw_breakpoint(struct perf_event *bp);
@ -90,18 +87,18 @@ static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
static inline struct perf_event *
register_user_hw_breakpoint(struct perf_event_attr *attr,
perf_callback_t triggered,
perf_overflow_handler_t triggered,
struct task_struct *tsk) { return NULL; }
static inline struct perf_event *
modify_user_hw_breakpoint(struct perf_event *bp,
struct perf_event_attr *attr) { return NULL; }
static inline struct perf_event *
register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
perf_callback_t triggered,
perf_overflow_handler_t triggered,
int cpu) { return NULL; }
static inline struct perf_event **
register_wide_hw_breakpoint(struct perf_event_attr *attr,
perf_callback_t triggered) { return NULL; }
perf_overflow_handler_t triggered) { return NULL; }
static inline int
register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; }
static inline int

13
include/linux/perf_event.h
View file

@ -565,10 +565,13 @@ struct perf_pending_entry {
void (*func)(struct perf_pending_entry *);
};
typedef void (*perf_callback_t)(struct perf_event *, void *);
struct perf_sample_data;
typedef void (*perf_callback_t)(struct perf_event *, void *);
typedef void (*perf_overflow_handler_t)(struct perf_event *, int,
struct perf_sample_data *,
struct pt_regs *regs);
/**
* struct perf_event - performance event kernel representation:
*/
@ -660,9 +663,7 @@ struct perf_event {
struct pid_namespace *ns;
u64 id;
void (*overflow_handler)(struct perf_event *event,
int nmi, struct perf_sample_data *data,
struct pt_regs *regs);
perf_overflow_handler_t overflow_handler;
#ifdef CONFIG_EVENT_PROFILE
struct event_filter *filter;
@ -779,7 +780,7 @@ extern struct perf_event *
perf_event_create_kernel_counter(struct perf_event_attr *attr,
int cpu,
pid_t pid,
perf_callback_t callback);
perf_overflow_handler_t callback);
extern u64 perf_event_read_value(struct perf_event *event,
u64 *enabled, u64 *running);

17
kernel/hw_breakpoint.c
View file

@ -259,7 +259,7 @@ void release_bp_slot(struct perf_event *bp)
}
int __register_perf_hw_breakpoint(struct perf_event *bp)
int register_perf_hw_breakpoint(struct perf_event *bp)
{
int ret;
@ -276,19 +276,12 @@ int __register_perf_hw_breakpoint(struct perf_event *bp)
* This is a quick hack that will be removed soon, once we remove
* the tmp breakpoints from ptrace
*/
if (!bp->attr.disabled || bp->callback == perf_bp_event)
if (!bp->attr.disabled || !bp->overflow_handler)
ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
return ret;
}
int register_perf_hw_breakpoint(struct perf_event *bp)
{
bp->callback = perf_bp_event;
return __register_perf_hw_breakpoint(bp);
}
/**
* register_user_hw_breakpoint - register a hardware breakpoint for user space
* @attr: breakpoint attributes
@ -297,7 +290,7 @@ int register_perf_hw_breakpoint(struct perf_event *bp)
*/
struct perf_event *
register_user_hw_breakpoint(struct perf_event_attr *attr,
perf_callback_t triggered,
perf_overflow_handler_t triggered,
struct task_struct *tsk)
{
return perf_event_create_kernel_counter(attr, -1, tsk->pid, triggered);
@ -322,7 +315,7 @@ modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
unregister_hw_breakpoint(bp);
return perf_event_create_kernel_counter(attr, -1, bp->ctx->task->pid,
bp->callback);
bp->overflow_handler);
}
EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
@ -347,7 +340,7 @@ EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
*/
struct perf_event **
register_wide_hw_breakpoint(struct perf_event_attr *attr,
perf_callback_t triggered)
perf_overflow_handler_t triggered)
{
struct perf_event **cpu_events, **pevent, *bp;
long err;

24
kernel/perf_event.c
View file

@ -4286,15 +4286,8 @@ static void bp_perf_event_destroy(struct perf_event *event)
static const struct pmu *bp_perf_event_init(struct perf_event *bp)
{
int err;
/*
* The breakpoint is already filled if we haven't created the counter
* through perf syscall
* FIXME: manage to get trigerred to NULL if it comes from syscalls
*/
if (!bp->callback)
err = register_perf_hw_breakpoint(bp);
else
err = __register_perf_hw_breakpoint(bp);
err = register_perf_hw_breakpoint(bp);
if (err)
return ERR_PTR(err);
@ -4390,7 +4383,7 @@ perf_event_alloc(struct perf_event_attr *attr,
struct perf_event_context *ctx,
struct perf_event *group_leader,
struct perf_event *parent_event,
perf_callback_t callback,
perf_overflow_handler_t overflow_handler,
gfp_t gfpflags)
{
const struct pmu *pmu;
@ -4433,10 +4426,10 @@ perf_event_alloc(struct perf_event_attr *attr,
event->state = PERF_EVENT_STATE_INACTIVE;
if (!callback && parent_event)
callback = parent_event->callback;
if (!overflow_handler && parent_event)
overflow_handler = parent_event->overflow_handler;
event->callback = callback;
event->overflow_handler = overflow_handler;
if (attr->disabled)
event->state = PERF_EVENT_STATE_OFF;
@ -4776,7 +4769,8 @@ err_put_context:
*/
struct perf_event *
perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
pid_t pid, perf_callback_t callback)
pid_t pid,
perf_overflow_handler_t overflow_handler)
{
struct perf_event *event;
struct perf_event_context *ctx;
@ -4793,7 +4787,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
}
event = perf_event_alloc(attr, cpu, ctx, NULL,
NULL, callback, GFP_KERNEL);
NULL, overflow_handler, GFP_KERNEL);
if (IS_ERR(event)) {
err = PTR_ERR(event);
goto err_put_context;

5
kernel/trace/trace_ksym.c
View file

@ -79,11 +79,12 @@ void ksym_collect_stats(unsigned long hbp_hit_addr)
}
#endif /* CONFIG_PROFILE_KSYM_TRACER */
void ksym_hbp_handler(struct perf_event *hbp, void *data)
void ksym_hbp_handler(struct perf_event *hbp, int nmi,
struct perf_sample_data *data,
struct pt_regs *regs)
{
struct ring_buffer_event *event;
struct ksym_trace_entry *entry;
struct pt_regs *regs = data;
struct ring_buffer *buffer;
int pc;

7
samples/hw_breakpoint/data_breakpoint.c
View file

@ -41,7 +41,9 @@ module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
" write operations on the kernel symbol");
static void sample_hbp_handler(struct perf_event *temp, void *data)
static void sample_hbp_handler(struct perf_event *bp, int nmi,
struct perf_sample_data *data,
struct pt_regs *regs)
{
printk(KERN_INFO "%s value is changed\n", ksym_name);
dump_stack();
@ -51,8 +53,9 @@ static void sample_hbp_handler(struct perf_event *temp, void *data)
static int __init hw_break_module_init(void)
{
int ret;
DEFINE_BREAKPOINT_ATTR(attr);
struct perf_event_attr attr;
hw_breakpoint_init(&attr);
attr.bp_addr = kallsyms_lookup_name(ksym_name);
attr.bp_len = HW_BREAKPOINT_LEN_4;
attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;