ftrace: align __mcount_loc sections

Impact: add alignment option for recordmcount.pl script

Align the __mcount_loc sections so that architectures with strict
alignment requirements need not worry about performing unaligned
accesses.

This fixes an issue where I was seeing unaligned accesses, which are not
supported on our architecture (the results of an unaligned access are
undefined).

Signed-off-by: Matt Fleming <matthew.fleming@imgtec.com>
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 6b9fe3eb836027bff637b912798b3b024a4baeba..eeac71c87c661042de5fb6a2707223b920db3a2b 100755 (executable)
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -134,6 +134,7 @@ my $section_regex;  # Find the start of a section
 my $function_regex;    # Find the name of a function
                        #    (return offset and func name)
 my $mcount_regex;      # Find the call site to mcount (return offset)
+my $alignment;         # The .align value to use for $mcount_section
 
 if ($arch eq "x86") {
     if ($bits == 64) {
@@ -148,6 +149,7 @@ if ($arch eq "x86_64") {
     $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount([+-]0x[0-9a-zA-Z]+)?\$";
     $type = ".quad";
+    $alignment = 8;
 
     # force flags for this arch
     $ld .= " -m elf_x86_64";
@@ -160,6 +162,7 @@ if ($arch eq "x86_64") {
     $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\smcount\$";
     $type = ".long";
+    $alignment = 4;
 
     # force flags for this arch
     $ld .= " -m elf_i386";
@@ -288,6 +291,7 @@ sub update_funcs
            open(FILE, ">$mcount_s") || die "can't create $mcount_s\n";
            $opened = 1;
            print FILE "\t.section $mcount_section,\"a\",\@progbits\n";
+           print FILE "\t.align $alignment\n";
        }
        printf FILE "\t%s %s + %d\n", $type, $ref_func, $offsets[$i] - $offset;
     }