44234adcdc
Currently, when ptrace needs to modify a breakpoint, like disabling it, changing its address, type or len, it calls modify_user_hw_breakpoint(). This latter will perform the heavy and racy task of unregistering the old breakpoint and registering a new one. This is racy as someone else might steal the reserved breakpoint slot under us, which is undesired as the breakpoint is only supposed to be modified, sometimes in the middle of a debugging workflow. We don't want our slot to be stolen in the middle. So instead of unregistering/registering the breakpoint, just disable it while we modify its breakpoint fields and re-enable it after if necessary. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Prasad <prasad@linux.vnet.ibm.com> LKML-Reference: <1260347148-5519-1-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
126 lines
3.5 KiB
C
126 lines
3.5 KiB
C
#ifndef _LINUX_HW_BREAKPOINT_H
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#define _LINUX_HW_BREAKPOINT_H
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enum {
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HW_BREAKPOINT_LEN_1 = 1,
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HW_BREAKPOINT_LEN_2 = 2,
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HW_BREAKPOINT_LEN_4 = 4,
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HW_BREAKPOINT_LEN_8 = 8,
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};
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enum {
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HW_BREAKPOINT_R = 1,
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HW_BREAKPOINT_W = 2,
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HW_BREAKPOINT_X = 4,
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};
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#ifdef __KERNEL__
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#include <linux/perf_event.h>
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#ifdef CONFIG_HAVE_HW_BREAKPOINT
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static inline void hw_breakpoint_init(struct perf_event_attr *attr)
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{
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memset(attr, 0, sizeof(*attr));
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attr->type = PERF_TYPE_BREAKPOINT;
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attr->size = sizeof(*attr);
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/*
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* As it's for in-kernel or ptrace use, we want it to be pinned
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* and to call its callback every hits.
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*/
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attr->pinned = 1;
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attr->sample_period = 1;
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}
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static inline unsigned long hw_breakpoint_addr(struct perf_event *bp)
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{
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return bp->attr.bp_addr;
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}
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static inline int hw_breakpoint_type(struct perf_event *bp)
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{
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return bp->attr.bp_type;
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}
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static inline int hw_breakpoint_len(struct perf_event *bp)
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{
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return bp->attr.bp_len;
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}
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extern struct perf_event *
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register_user_hw_breakpoint(struct perf_event_attr *attr,
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perf_overflow_handler_t triggered,
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struct task_struct *tsk);
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/* FIXME: only change from the attr, and don't unregister */
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extern int
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modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr);
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/*
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* Kernel breakpoints are not associated with any particular thread.
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*/
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extern struct perf_event *
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register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
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perf_overflow_handler_t triggered,
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int cpu);
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extern struct perf_event **
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register_wide_hw_breakpoint(struct perf_event_attr *attr,
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perf_overflow_handler_t triggered);
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extern int register_perf_hw_breakpoint(struct perf_event *bp);
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extern int __register_perf_hw_breakpoint(struct perf_event *bp);
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extern void unregister_hw_breakpoint(struct perf_event *bp);
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extern void unregister_wide_hw_breakpoint(struct perf_event **cpu_events);
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extern int reserve_bp_slot(struct perf_event *bp);
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extern void release_bp_slot(struct perf_event *bp);
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extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk);
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static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
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{
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return &bp->hw.info;
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}
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#else /* !CONFIG_HAVE_HW_BREAKPOINT */
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static inline struct perf_event *
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register_user_hw_breakpoint(struct perf_event_attr *attr,
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perf_overflow_handler_t triggered,
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struct task_struct *tsk) { return NULL; }
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static inline int
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modify_user_hw_breakpoint(struct perf_event *bp,
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struct perf_event_attr *attr) { return NULL; }
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static inline struct perf_event *
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register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
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perf_overflow_handler_t triggered,
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int cpu) { return NULL; }
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static inline struct perf_event **
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register_wide_hw_breakpoint(struct perf_event_attr *attr,
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perf_overflow_handler_t triggered) { return NULL; }
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static inline int
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register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; }
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static inline int
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__register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; }
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static inline void unregister_hw_breakpoint(struct perf_event *bp) { }
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static inline void
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unregister_wide_hw_breakpoint(struct perf_event **cpu_events) { }
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static inline int
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reserve_bp_slot(struct perf_event *bp) {return -ENOSYS; }
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static inline void release_bp_slot(struct perf_event *bp) { }
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static inline void flush_ptrace_hw_breakpoint(struct task_struct *tsk) { }
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static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
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{
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return NULL;
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}
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#endif /* CONFIG_HAVE_HW_BREAKPOINT */
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#endif /* __KERNEL__ */
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#endif /* _LINUX_HW_BREAKPOINT_H */
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