perf core: Add a 'nr' field to perf_event_callchain_context

We will use it to count how many addresses are in the entry->ip[] array,
excluding PERF_CONTEXT_{KERNEL,USER,etc} entries, so that we can really
return the number of entries specified by the user via the relevant
sysctl, kernel.perf_event_max_contexts, or via the per event
perf_event_attr.sample_max_stack knob.

This way we keep the perf_sample->ip_callchain->nr meaning, that is the
number of entries, be it real addresses or PERF_CONTEXT_ entries, while
honouring the max_stack knobs, i.e. the end result will be max_stack
entries if we have at least that many entries in a given stack trace.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-s8teto51tdqvlfhefndtat9r@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

9 files changed, 18 insertions, 17 deletions

diff --git a/arch/arm/kernel/perf_callchain.c b/arch/arm/kernel/perf_callchain.c
index bc552e813e7b..22bf1f64d99a 100644
--- a/arch/arm/kernel/perf_callchain.c
+++ b/arch/arm/kernel/perf_callchain.c
@@ -75,7 +75,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs
 
         tail = (struct frame_tail __user *)regs->ARM_fp - 1;
 
-        while ((entry->entry->nr < entry->max_stack) &&
+        while ((entry->nr < entry->max_stack) &&
                tail && !((unsigned long)tail & 0x3))
                 tail = user_backtrace(tail, entry);
 }
diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c
index 0d60150057cf..713ca824f266 100644
--- a/arch/arm64/kernel/perf_callchain.c
+++ b/arch/arm64/kernel/perf_callchain.c
@@ -122,7 +122,7 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 
                 tail = (struct frame_tail __user *)regs->regs[29];
 
-                while (entry->entry->nr < entry->max_stack &&
+                while (entry->nr < entry->max_stack &&
                        tail && !((unsigned long)tail & 0xf))
                         tail = user_backtrace(tail, entry);
         } else {
@@ -132,7 +132,7 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 
                 tail = (struct compat_frame_tail __user *)regs->compat_fp - 1;
 
-                while ((entry->entry->nr < entry->max_stack) &&
+                while ((entry->nr < entry->max_stack) &&
                         tail && !((unsigned long)tail & 0x3))
                         tail = compat_user_backtrace(tail, entry);
 #endif
diff --git a/arch/metag/kernel/perf_callchain.c b/arch/metag/kernel/perf_callchain.c
index b3261a98b15b..3e8e048040df 100644
--- a/arch/metag/kernel/perf_callchain.c
+++ b/arch/metag/kernel/perf_callchain.c
@@ -65,7 +65,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs
 
         --frame;
 
-        while ((entry->entry->nr < entry->max_stack) && frame)
+        while ((entry->nr < entry->max_stack) && frame)
                 frame = user_backtrace(frame, entry);
 }
 
diff --git a/arch/mips/kernel/perf_event.c b/arch/mips/kernel/perf_event.c
index 22395c7d7030..d64056e0bb56 100644
--- a/arch/mips/kernel/perf_event.c
+++ b/arch/mips/kernel/perf_event.c
@@ -35,7 +35,7 @@ static void save_raw_perf_callchain(struct perf_callchain_entry_ctx *entry,
                 addr = *sp++;
                 if (__kernel_text_address(addr)) {
                         perf_callchain_store(entry, addr);
-                        if (entry->entry->nr >= entry->max_stack)
+                        if (entry->nr >= entry->max_stack)
                                 break;
                 }
         }
@@ -59,7 +59,7 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
         }
         do {
                 perf_callchain_store(entry, pc);
-                if (entry->entry->nr >= entry->max_stack)
+                if (entry->nr >= entry->max_stack)
                         break;
                 pc = unwind_stack(current, &sp, pc, &ra);
         } while (pc);
diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
index c9260c1dfdbc..f68f213dc36c 100644
--- a/arch/powerpc/perf/callchain.c
+++ b/arch/powerpc/perf/callchain.c
@@ -247,7 +247,7 @@ static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
         sp = regs->gpr[1];
         perf_callchain_store(entry, next_ip);
 
-        while (entry->entry->nr < entry->max_stack) {
+        while (entry->nr < entry->max_stack) {
                 fp = (unsigned long __user *) sp;
                 if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
                         return;
@@ -453,7 +453,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
         sp = regs->gpr[1];
         perf_callchain_store(entry, next_ip);
 
-        while (entry->entry->nr < entry->max_stack) {
+        while (entry->nr < entry->max_stack) {
                 fp = (unsigned int __user *) (unsigned long) sp;
                 if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
                         return;
diff --git a/arch/sparc/kernel/perf_event.c b/arch/sparc/kernel/perf_event.c
index bcc5376db74b..710f3278d448 100644
--- a/arch/sparc/kernel/perf_event.c
+++ b/arch/sparc/kernel/perf_event.c
@@ -1756,7 +1756,7 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
                         }
                 }
 #endif
-        } while (entry->entry->nr < entry->max_stack);
+        } while (entry->nr < entry->max_stack);
 }
 
 static inline int
@@ -1790,7 +1790,7 @@ static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
                 pc = sf.callers_pc;
                 ufp = (unsigned long)sf.fp + STACK_BIAS;
                 perf_callchain_store(entry, pc);
-        } while (entry->entry->nr < entry->max_stack);
+        } while (entry->nr < entry->max_stack);
 }
 
 static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
@@ -1822,7 +1822,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
                         ufp = (unsigned long)sf.fp;
                 }
                 perf_callchain_store(entry, pc);
-        } while (entry->entry->nr < entry->max_stack);
+        } while (entry->nr < entry->max_stack);
 }
 
 void
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 07f2b01cfb72..5de96a18cd9c 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2283,7 +2283,7 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent
 
         fp = compat_ptr(ss_base + regs->bp);
         pagefault_disable();
-        while (entry->entry->nr < entry->max_stack) {
+        while (entry->nr < entry->max_stack) {
                 unsigned long bytes;
                 frame.next_frame     = 0;
                 frame.return_address = 0;
@@ -2343,7 +2343,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs
                 return;
 
         pagefault_disable();
-        while (entry->entry->nr < entry->max_stack) {
+        while (entry->nr < entry->max_stack) {
                 unsigned long bytes;
                 frame.next_frame             = NULL;
                 frame.return_address = 0;
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index dbd18246b36e..3803bb1a862b 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -64,6 +64,7 @@ struct perf_callchain_entry {
 struct perf_callchain_entry_ctx {
         struct perf_callchain_entry *entry;
         u32                         max_stack;
+        u32                         nr;
 };
 
 struct perf_raw_record {
@@ -1080,9 +1081,10 @@ extern int sysctl_perf_event_max_stack;
 
 static inline int perf_callchain_store(struct perf_callchain_entry_ctx *ctx, u64 ip)
 {
-        struct perf_callchain_entry *entry = ctx->entry;
-        if (entry->nr < ctx->max_stack) {
+        if (ctx->nr < ctx->max_stack) {
+                struct perf_callchain_entry *entry = ctx->entry;
                 entry->ip[entry->nr++] = ip;
+                ++ctx->nr;
                 return 0;
         } else {
                 return -1; /* no more room, stop walking the stack */
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index af95ad92893a..8774ff86debb 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -196,8 +196,7 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
 
         ctx.entry     = entry;
         ctx.max_stack = max_stack;
-
-        entry->nr = init_nr;
+        ctx.nr        = entry->nr = init_nr;
 
         if (kernel && !user_mode(regs)) {
                 if (add_mark)