perf: generalize perf_callchain

. avoid walking the stack when there is no room left in the buffer
. generalize get_perf_callchain() to be called from bpf helper

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 20 insertions, 13 deletions

diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 70bbe39..7c247e7 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -37,7 +37,7 @@ print_context_stack_bp(struct thread_info *tinfo,
 /* Generic stack tracer with callbacks */
 
 struct stacktrace_ops {
-	void (*address)(void *data, unsigned long address, int reliable);
+	int (*address)(void *data, unsigned long address, int reliable);
 	/* On negative return stop dumping */
 	int (*stack)(void *data, char *name);
 	walk_stack_t	walk_stack;
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 1b443db..d276b31 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2180,11 +2180,11 @@ static int backtrace_stack(void *data, char *name)
 	return 0;
 }
 
-static void backtrace_address(void *data, unsigned long addr, int reliable)
+static int backtrace_address(void *data, unsigned long addr, int reliable)
 {
 	struct perf_callchain_entry *entry = data;
 
-	perf_callchain_store(entry, addr);
+	return perf_callchain_store(entry, addr);
 }
 
 static const struct stacktrace_ops backtrace_ops = {
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 9c30acf..0d1ff4b 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -135,7 +135,8 @@ print_context_stack_bp(struct thread_info *tinfo,
 		if (!__kernel_text_address(addr))
 			break;
 
-		ops->address(data, addr, 1);
+		if (ops->address(data, addr, 1))
+			break;
 		frame = frame->next_frame;
 		ret_addr = &frame->return_address;
 		print_ftrace_graph_addr(addr, data, ops, tinfo, graph);
@@ -154,10 +155,11 @@ static int print_trace_stack(void *data, char *name)
 /*
  * Print one address/symbol entries per line.
  */
-static void print_trace_address(void *data, unsigned long addr, int reliable)
+static int print_trace_address(void *data, unsigned long addr, int reliable)
 {
 	touch_nmi_watchdog();
 	printk_stack_address(addr, reliable, data);
+	return 0;
 }
 
 static const struct stacktrace_ops print_trace_ops = {
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index fdd0c64..9ee98ee 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -14,30 +14,34 @@ static int save_stack_stack(void *data, char *name)
 	return 0;
 }
 
-static void
+static int
 __save_stack_address(void *data, unsigned long addr, bool reliable, bool nosched)
 {
 	struct stack_trace *trace = data;
 #ifdef CONFIG_FRAME_POINTER
 	if (!reliable)
-		return;
+		return 0;
 #endif
 	if (nosched && in_sched_functions(addr))
-		return;
+		return 0;
 	if (trace->skip > 0) {
 		trace->skip--;
-		return;
+		return 0;
 	}
-	if (trace->nr_entries < trace->max_entries)
+	if (trace->nr_entries < trace->max_entries) {
 		trace->entries[trace->nr_entries++] = addr;
+		return 0;
+	} else {
+		return -1; /* no more room, stop walking the stack */
+	}
 }
 
-static void save_stack_address(void *data, unsigned long addr, int reliable)
+static int save_stack_address(void *data, unsigned long addr, int reliable)
 {
 	return __save_stack_address(data, addr, reliable, false);
 }
 
-static void
+static int
 save_stack_address_nosched(void *data, unsigned long addr, int reliable)
 {
 	return __save_stack_address(data, addr, reliable, true);
diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
index 4e664bd..cb31a44 100644
--- a/arch/x86/oprofile/backtrace.c
+++ b/arch/x86/oprofile/backtrace.c
@@ -23,12 +23,13 @@ static int backtrace_stack(void *data, char *name)
 	return 0;
 }
 
-static void backtrace_address(void *data, unsigned long addr, int reliable)
+static int backtrace_address(void *data, unsigned long addr, int reliable)
 {
 	unsigned int *depth = data;
 
 	if ((*depth)--)
 		oprofile_add_trace(addr);
+	return 0;
 }
 
 static struct stacktrace_ops backtrace_ops = {