3 files changed, 49 insertions, 6 deletions

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 499d9e933f8e..f5a19548be12 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -66,7 +66,7 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
         /* check sanity of attributes */
         if (attr->max_entries == 0 || attr->key_size != 4 ||
             value_size < 8 || value_size % 8 ||
-            value_size / 8 > PERF_MAX_STACK_DEPTH)
+            value_size / 8 > sysctl_perf_event_max_stack)
                 return ERR_PTR(-EINVAL);
 
         /* hash table size must be power of 2 */
@@ -124,8 +124,8 @@ static u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
         struct perf_callchain_entry *trace;
         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
         u32 max_depth = map->value_size / 8;
-        /* stack_map_alloc() checks that max_depth <= PERF_MAX_STACK_DEPTH */
-        u32 init_nr = PERF_MAX_STACK_DEPTH - max_depth;
+        /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
+        u32 init_nr = sysctl_perf_event_max_stack - max_depth;
         u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
         u32 hash, id, trace_nr, trace_len;
         bool user = flags & BPF_F_USER_STACK;
@@ -143,7 +143,7 @@ static u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
                 return -EFAULT;
 
         /* get_perf_callchain() guarantees that trace->nr >= init_nr
-         * and trace-nr <= PERF_MAX_STACK_DEPTH, so trace_nr <= max_depth
+         * and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
          */
         trace_nr = trace->nr - init_nr;
 
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 343c22f5e867..b9325e7dcba1 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -18,6 +18,14 @@ struct callchain_cpus_entries {
         struct perf_callchain_entry     *cpu_entries[0];
 };
 
+int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
+
+static inline size_t perf_callchain_entry__sizeof(void)
+{
+        return (sizeof(struct perf_callchain_entry) +
+                sizeof(__u64) * sysctl_perf_event_max_stack);
+}
+
 static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
 static atomic_t nr_callchain_events;
 static DEFINE_MUTEX(callchain_mutex);
@@ -73,7 +81,7 @@ static int alloc_callchain_buffers(void)
         if (!entries)
                 return -ENOMEM;
 
-        size = sizeof(struct perf_callchain_entry) * PERF_NR_CONTEXTS;
+        size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS;
 
         for_each_possible_cpu(cpu) {
                 entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL,
@@ -147,7 +155,8 @@ static struct perf_callchain_entry *get_callchain_entry(int *rctx)
 
         cpu = smp_processor_id();
 
-        return &entries->cpu_entries[cpu][*rctx];
+        return (((void *)entries->cpu_entries[cpu]) +
+                (*rctx * perf_callchain_entry__sizeof()));
 }
 
 static void
@@ -215,3 +224,25 @@ exit_put:
 
         return entry;
 }
+
+int perf_event_max_stack_handler(struct ctl_table *table, int write,
+                                 void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        int new_value = sysctl_perf_event_max_stack, ret;
+        struct ctl_table new_table = *table;
+
+        new_table.data = &new_value;
+        ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos);
+        if (ret || !write)
+                return ret;
+
+        mutex_lock(&callchain_mutex);
+        if (atomic_read(&nr_callchain_events))
+                ret = -EBUSY;
+        else
+                sysctl_perf_event_max_stack = new_value;
+
+        mutex_unlock(&callchain_mutex);
+
+        return ret;
+}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 725587f10667..c8b318663525 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -130,6 +130,9 @@ static int one_thousand = 1000;
 #ifdef CONFIG_PRINTK
 static int ten_thousand = 10000;
 #endif
+#ifdef CONFIG_PERF_EVENTS
+static int six_hundred_forty_kb = 640 * 1024;
+#endif
 
 /* this is needed for the proc_doulongvec_minmax of vm_dirty_bytes */
 static unsigned long dirty_bytes_min = 2 * PAGE_SIZE;
@@ -1144,6 +1147,15 @@ static struct ctl_table kern_table[] = {
                 .extra1         = &zero,
                 .extra2         = &one_hundred,
         },
+        {
+                .procname       = "perf_event_max_stack",
+                .data           = NULL, /* filled in by handler */
+                .maxlen         = sizeof(sysctl_perf_event_max_stack),
+                .mode           = 0644,
+                .proc_handler   = perf_event_max_stack_handler,
+                .extra1         = &zero,
+                .extra2         = &six_hundred_forty_kb,
+        },
 #endif
 #ifdef CONFIG_KMEMCHECK
         {