Messages in this thread | | | Subject | Re: [PATCH v2 14/16] powerpc/watchpoint: Don't allow concurrent perf and ptrace events | From | Christophe Leroy <> | Date | Wed, 1 Apr 2020 08:52:16 +0200 |
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Le 01/04/2020 à 08:13, Ravi Bangoria a écrit : > With Book3s DAWR, ptrace and perf watchpoints on powerpc behaves > differently. Ptrace watchpoint works in one-shot mode and generates > signal before executing instruction. It's ptrace user's job to > single-step the instruction and re-enable the watchpoint. OTOH, in > case of perf watchpoint, kernel emulates/single-steps the instruction > and then generates event. If perf and ptrace creates two events with > same or overlapping address ranges, it's ambiguous to decide who > should single-step the instruction. Because of this issue, don't > allow perf and ptrace watchpoint at the same time if their address > range overlaps. > > Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com> > --- > arch/powerpc/include/asm/hw_breakpoint.h | 2 + > arch/powerpc/kernel/hw_breakpoint.c | 222 +++++++++++++++++++++++ > kernel/events/hw_breakpoint.c | 16 ++ > 3 files changed, 240 insertions(+) > > diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h > index abc4603c0efe..9d3bd1169591 100644 > --- a/arch/powerpc/include/asm/hw_breakpoint.h > +++ b/arch/powerpc/include/asm/hw_breakpoint.h > @@ -70,6 +70,8 @@ extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused, > unsigned long val, void *data); > int arch_install_hw_breakpoint(struct perf_event *bp); > void arch_uninstall_hw_breakpoint(struct perf_event *bp); > +int arch_reserve_bp_slot(struct perf_event *bp); > +void arch_release_bp_slot(struct perf_event *bp); > void arch_unregister_hw_breakpoint(struct perf_event *bp); > void hw_breakpoint_pmu_read(struct perf_event *bp); > extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk); > diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c > index 07a6cdea84ed..f813acb0d9f0 100644 > --- a/arch/powerpc/kernel/hw_breakpoint.c > +++ b/arch/powerpc/kernel/hw_breakpoint.c > @@ -123,6 +123,228 @@ static bool is_ptrace_bp(struct perf_event *bp) > return bp->overflow_handler == ptrace_triggered; > } > > +struct breakpoint { > + struct list_head list; > + struct perf_event *bp; > + bool ptrace_bp; > +}; > + > +static DEFINE_PER_CPU(struct breakpoint *, cpu_bps[HBP_NUM_MAX]); > +static LIST_HEAD(task_bps); > + > +static struct breakpoint *alloc_breakpoint(struct perf_event *bp) > +{ > + struct breakpoint *tmp; > + > + tmp = kzalloc(sizeof(*tmp), GFP_KERNEL); > + if (!tmp) > + return ERR_PTR(-ENOMEM); > + tmp->bp = bp; > + tmp->ptrace_bp = is_ptrace_bp(bp); > + return tmp; > +} > + > +static bool bp_addr_range_overlap(struct perf_event *bp1, struct perf_event *bp2) > +{ > + __u64 bp1_saddr, bp1_eaddr, bp2_saddr, bp2_eaddr; > + > + bp1_saddr = ALIGN_DOWN(bp1->attr.bp_addr, HW_BREAKPOINT_SIZE); > + bp1_eaddr = ALIGN(bp1->attr.bp_addr + bp1->attr.bp_len, HW_BREAKPOINT_SIZE) - 1; > + bp2_saddr = ALIGN_DOWN(bp2->attr.bp_addr, HW_BREAKPOINT_SIZE); > + bp2_eaddr = ALIGN(bp2->attr.bp_addr + bp2->attr.bp_len, HW_BREAKPOINT_SIZE) - 1; > + > + return (bp1_saddr <= bp2_eaddr && bp1_eaddr >= bp2_saddr);
Could avoid the - 1 on bp1_eaddr and bp2_eaddr by doing:
return (bp1_saddr < bp2_eaddr && bp1_eaddr > bp2_saddr);
Christophe
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