[PATCH 2/3] perf callchain: Stop resolving callchains after invalid address

[Namhyung Kim]

Unwinding optimized binaries using frame pointer gives garbage.  Check
callchain address and stop if it's under vm.mmap_min_addr sysctl value.

Before:
  $ perf report --stdio --no-children -g callee
  ...

   1.37%  perf    [kernel.vmlinux]    [k] smp_call_function_single
               |
               ---smp_call_function_single
                  _perf_event_enable
                  perf_event_for_each_child
                  perf_ioctl
                  do_vfs_ioctl
                  sys_ioctl
                  entry_SYSCALL_64_fastpath
                  __GI___ioctl
                  0
                  0
                  0x1c5aa70
                  0x1c5b910
                  0x1c5aa70
                  0x1c5b910
                  0x1c5aa70
                  0x1c5b910
                  0x1c5aa70
                  0x1c5b910
                  0x1c5aa70
                  0x1c5b910
		  ...

After:
  $ perf report --stdio --no-children -g callee
  ...

   1.37%  perf    [kernel.vmlinux]    [k] smp_call_function_single
               |
               ---smp_call_function_single
                  _perf_event_enable
                  perf_event_for_each_child
                  perf_ioctl
                  do_vfs_ioctl
                  sys_ioctl
                  entry_SYSCALL_64_fastpath
                  __GI___ioctl

  $ perf report --stdio --no-children -g caller
  ...

   1.37%  perf    [kernel.vmlinux]    [k] smp_call_function_single
               |
               ---__GI__ioctl
                  entry_SYSCALL_64_fastpath
                  sys_ioctl
                  do_vfs_ioctl
                  perf_ioctl
                  perf_event_for_each_child
                  _perf_event_enable
                  smp_call_function_single

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/perf.c         |  6 ++++++
 tools/perf/util/machine.c | 13 +++++++++++++
 tools/perf/util/util.c    |  1 +
 tools/perf/util/util.h    |  1 +
 4 files changed, 21 insertions(+)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 4bee53c3f796..0075a6d38e3a 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -18,6 +18,7 @@
 #include "util/bpf-loader.h"
 #include "util/debug.h"
 #include <api/fs/tracing_path.h>
+#include <api/fs/fs.h>
 #include <pthread.h>
 
 const char perf_usage_string[] =
@@ -528,11 +529,16 @@ int main(int argc, const char **argv)
 {
 	const char *cmd;
 	char sbuf[STRERR_BUFSIZE];
+	int min_addr;
 
 	/* The page_size is placed in util object. */
 	page_size = sysconf(_SC_PAGE_SIZE);
 	cacheline_size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
 
+	if (sysctl__read_int("vm/mmap_min_addr", &min_addr) < 0)
+		min_addr = page_size;
+	mmap_min_addr = min_addr;
+
 	cmd = perf_extract_argv0_path(argv[0]);
 	if (!cmd)
 		cmd = "perf-help";
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 7f5071a4d9aa..0a2f35e0d737 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1860,6 +1860,19 @@ static int thread__resolve_callchain_sample(struct thread *thread,
 #endif
 		ip = chain->ips[j];
 
+		/*
+		 * Callchain value under mmap_min_addr means it's broken
+		 * or the end of callchain.  Stop.
+		 */
+		if (ip < mmap_min_addr) {
+			if (callchain_param.order == ORDER_CALLEE)
+				break;
+
+			/* ignore current callchains for CALLER order */
+			callchain_cursor_reset(&callchain_cursor);
+			continue;
+		}
+
 		err = add_callchain_ip(thread, parent, root_al, &cpumode, ip);
 
 		if (err)
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 75759aebc7b8..8e198acd9fa6 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -30,6 +30,7 @@ struct callchain_param	callchain_param = {
  */
 unsigned int page_size;
 int cacheline_size;
+unsigned long mmap_min_addr;
 
 bool test_attr__enabled;
 
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index dcc659017976..506d4dbb58be 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -281,6 +281,7 @@ void sighandler_dump_stack(int sig);
 
 extern unsigned int page_size;
 extern int cacheline_size;
+extern unsigned long mmap_min_addr;
 
 void get_term_dimensions(struct winsize *ws);
 void set_term_quiet_input(struct termios *old);
-- 
2.6.2

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