ftrace: dynamic ftrace process only text section

The text section stays in memory without ever leaving. With the exception
of modules, but modules know how to handle that case. With the dynamic
ftrace tracer, we need to make sure that it does not try to modify code
that no longer exists. The only safe section is .text.

This patch changes the recordmcount script to only record the mcount calls
in the .text sections.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index c1c618c..6b9fe3e 100755 (executable)
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -109,6 +109,11 @@ if ($#ARGV < 6) {
 my ($arch, $bits, $objdump, $objcopy, $cc,
     $ld, $nm, $rm, $mv, $inputfile) = @ARGV;
 
+# Acceptable sections to record.
+my %text_sections = (
+     ".text" => 1,
+);
+
 $objdump = "objdump" if ((length $objdump) == 0);
 $objcopy = "objcopy" if ((length $objcopy) == 0);
 $cc = "gcc" if ((length $cc) == 0);
@@ -139,7 +144,7 @@ if ($arch eq "x86") {
 }
 
 if ($arch eq "x86_64") {
-    $section_regex = "Disassembly of section";
+    $section_regex = "Disassembly of section\\s+(\\S+):";
     $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
     $type = ".quad";
@@ -151,7 +156,7 @@ if ($arch eq "x86_64") {
     $cc .= " -m64";
 
 } elsif ($arch eq "i386") {
-    $section_regex = "Disassembly of section";
+    $section_regex = "Disassembly of section\\s+(\\S+):";
     $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
     $type = ".long";
@@ -298,7 +303,13 @@ my $text;
 while (<IN>) {
     # is it a section?
     if (/$section_regex/) {
-       $read_function = 1;
+
+       # Only record text sections that we know are safe
+       if (defined($text_sections{$1})) {
+           $read_function = 1;
+       } else {
+           $read_function = 0;
+       }
        # print out any recorded offsets
        update_funcs() if ($text_found);