perf_counter: Make callchain samples extensible

Before exposing upstream tools to a callchain-samples ABI, tidy it
up to make it more extensible in the future:

Use markers in the IP chain to denote context, use (u64)-1..-4095 range
for these context markers because we use them for ERR_PTR(), so these
addresses are unlikely to be mapped.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 23 insertions, 34 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index ce1ae3f1f86c..76dfef23f789 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -1555,9 +1555,9 @@ const struct pmu *hw_perf_counter_init(struct perf_counter *counter)
  */
 
 static inline
-void callchain_store(struct perf_callchain_entry *entry, unsigned long ip)
+void callchain_store(struct perf_callchain_entry *entry, u64 ip)
 {
-        if (entry->nr < MAX_STACK_DEPTH)
+        if (entry->nr < PERF_MAX_STACK_DEPTH)
                 entry->ip[entry->nr++] = ip;
 }
 
@@ -1602,22 +1602,10 @@ static const struct stacktrace_ops backtrace_ops = {
 static void
 perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry)
 {
-        unsigned long bp;
-        char *stack;
-        int nr = entry->nr;
-
+        callchain_store(entry, PERF_CONTEXT_KERNEL);
         callchain_store(entry, regs->ip);
 
-        stack = ((char *)regs + sizeof(struct pt_regs));
-#ifdef CONFIG_FRAME_POINTER
-        get_bp(bp);
-#else
-        bp = 0;
-#endif
-
-        dump_trace(NULL, regs, (void *)&stack, bp, &backtrace_ops, entry);
-
-        entry->kernel = entry->nr - nr;
+        dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
 }
 
 /*
@@ -1669,16 +1657,16 @@ perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry)
 {
         struct stack_frame frame;
         const void __user *fp;
-        int nr = entry->nr;
 
         if (!user_mode(regs))
                 regs = task_pt_regs(current);
 
         fp = (void __user *)regs->bp;
 
+        callchain_store(entry, PERF_CONTEXT_USER);
         callchain_store(entry, regs->ip);
 
-        while (entry->nr < MAX_STACK_DEPTH) {
+        while (entry->nr < PERF_MAX_STACK_DEPTH) {
                 frame.next_frame             = NULL;
                 frame.return_address = 0;
 
@@ -1691,8 +1679,6 @@ perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry)
                 callchain_store(entry, frame.return_address);
                 fp = frame.next_frame;
         }
-
-        entry->user = entry->nr - nr;
 }
 
 static void
@@ -1728,9 +1714,6 @@ struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
                 entry = &__get_cpu_var(irq_entry);
 
         entry->nr = 0;
-        entry->hv = 0;
-        entry->kernel = 0;
-        entry->user = 0;
 
         perf_do_callchain(regs, entry);
 
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 0765e8e69843..e7e7e0242767 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -343,23 +343,22 @@ enum perf_event_type {
          *      { u64                   nr;
          *        { u64 id, val; }      cnt[nr];  } && PERF_SAMPLE_GROUP
          *
-         *      { u16                   nr,
-         *                              hv,
-         *                              kernel,
-         *                              user;
+         *      { u64                   nr,
          *        u64                   ips[nr];  } && PERF_SAMPLE_CALLCHAIN
          * };
          */
 };
 
-#define MAX_STACK_DEPTH                 255
+enum perf_callchain_context {
+        PERF_CONTEXT_HV                 = (__u64)-32,
+        PERF_CONTEXT_KERNEL             = (__u64)-128,
+        PERF_CONTEXT_USER               = (__u64)-512,
 
-struct perf_callchain_entry {
-        __u16                           nr;
-        __u16                           hv;
-        __u16                           kernel;
-        __u16                           user;
-        __u64                           ip[MAX_STACK_DEPTH];
+        PERF_CONTEXT_GUEST              = (__u64)-2048,
+        PERF_CONTEXT_GUEST_KERNEL       = (__u64)-2176,
+        PERF_CONTEXT_GUEST_USER         = (__u64)-2560,
+
+        PERF_CONTEXT_MAX                = (__u64)-4095,
 };
 
 #ifdef __KERNEL__
@@ -381,6 +380,13 @@ struct perf_callchain_entry {
 #include <linux/pid_namespace.h>
 #include <asm/atomic.h>
 
+#define PERF_MAX_STACK_DEPTH            255
+
+struct perf_callchain_entry {
+        __u64                           nr;
+        __u64                           ip[PERF_MAX_STACK_DEPTH];
+};
+
 struct task_struct;
 
 /**