Messages in this thread Patch in this message | | | Subject | [PATCH] perf_counter: Default to higher paranoia level | From | Peter Zijlstra <> | Date | Mon, 17 Aug 2009 15:03:44 +0200 |
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Change the default permissions on perf counters.
The new default will disallow regular users to create cpu-wide counters, and will anonymize kernel IPs for task samples.
This will allow a user to profile his own applications and still know the proportion of the kernel events, but does not expose kernel IPs.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- arch/x86/kernel/cpu/perf_counter.c | 6 ++++++ include/linux/perf_counter.h | 1 + kernel/perf_counter.c | 27 ++++++++++++++++++++------- 3 files changed, 27 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 396e35d..0fe1126 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -2153,7 +2153,13 @@ static const struct stacktrace_ops backtrace_ops = { static void perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry) { + u64 anon_ip = perf_paranoid_anon_ip(); + callchain_store(entry, PERF_CONTEXT_KERNEL); + if (anon_ip) { + callchain_store(entry, anon_ip); + return; + } callchain_store(entry, regs->ip); dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry); diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 9ba1822..b74b1c3 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -754,6 +754,7 @@ static inline void perf_counter_mmap(struct vm_area_struct *vma) extern void perf_counter_comm(struct task_struct *tsk); extern void perf_counter_fork(struct task_struct *tsk); +extern unsigned long perf_paranoid_anon_ip(void); extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs); extern int sysctl_perf_counter_paranoid; diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index b8fe739..8daf760 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -48,18 +48,29 @@ static atomic_t nr_task_counters __read_mostly; * perf counter paranoia level: * 0 - not paranoid * 1 - disallow cpu counters to unpriv - * 2 - disallow kernel profiling to unpriv + * 2 - anonymize kernel RIPs to unpriv + * 3 - disallow kernel profiling to unpriv */ -int sysctl_perf_counter_paranoid __read_mostly; +int sysctl_perf_counter_paranoid __read_mostly = 2; static inline bool perf_paranoid_cpu(void) { - return sysctl_perf_counter_paranoid > 0; + return !capable(CAP_SYS_ADMIN) && sysctl_perf_counter_paranoid > 0; +} + +static inline bool perf_paranoid_anon(void) +{ + return !capable(CAP_SYS_ADMIN) && sysctl_perf_counter_paranoid > 1; } static inline bool perf_paranoid_kernel(void) { - return sysctl_perf_counter_paranoid > 1; + return !capable(CAP_SYS_ADMIN) && sysctl_perf_counter_paranoid > 2; +} + +unsigned long perf_paranoid_anon_ip(void) +{ + return perf_paranoid_anon() ? _THIS_IP_ : 0; } int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */ @@ -1571,7 +1582,7 @@ static struct perf_counter_context *find_get_context(pid_t pid, int cpu) */ if (cpu != -1) { /* Must be root to operate on a CPU counter: */ - if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN)) + if (perf_paranoid_cpu()) return ERR_PTR(-EACCES); if (cpu < 0 || cpu > num_possible_cpus()) @@ -2841,7 +2852,9 @@ void perf_counter_output(struct perf_counter *counter, int nmi, header.misc |= perf_misc_flags(data->regs); if (sample_type & PERF_SAMPLE_IP) { - ip = perf_instruction_pointer(data->regs); + ip = perf_paranoid_anon_ip(); + if (!ip || user_mode(data->regs)) + ip = perf_instruction_pointer(data->regs); header.size += sizeof(ip); } @@ -4227,7 +4240,7 @@ SYSCALL_DEFINE5(perf_counter_open, return ret; if (!attr.exclude_kernel) { - if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN)) + if (perf_paranoid_kernel()) return -EACCES; }
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