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authorSteven Rostedt <srostedt@redhat.com>2009-01-16 23:18:31 -0500
committerIngo Molnar <mingo@elte.hu>2009-01-18 14:15:26 -0500
commitb43f70933e7753a284733d5ae355f6778bd118ce (patch)
treefa58ff17461dcc7104d6390742c99d120cc95c16 /scripts
parent4092762aebfe55c1f8e31440b80a053c2dbe519b (diff)
ftrace: test for running of recordmcount.pl twice on an object
Impact: fix failure of dynamic function tracer selftest In a course of development, a developer does several makes on their kernel. Sometimes, the make might do something abnormal. In the case of running the recordmcount.pl script on an object twice, the script will duplicate all the calls to mcount in the __mcount_loc section. On boot up, the dynamic function tracer is careful when it modifies code, and performs several consistency checks. One is to not modify the call site if it is not what it expects it to be. If a function call site is listed twice, the first entry will convert the site to a nop, and the second will fail because it expected to see a call to mcount, but instead it sees a nop. Thus, the function tracer is disabled. Eric Sesterhenn reported seeing: [ 1.055440] ftrace: converting mcount calls to 0f 1f 44 00 00 [ 1.055568] ftrace: allocating 29418 entries in 116 pages [ 1.061000] ------------[ cut here ]------------ [ 1.061000] WARNING: at kernel/trace/ftrace.c:441 [...] [ 1.060000] ---[ end trace 4eaa2a86a8e2da23 ]--- [ 1.060000] ftrace failed to modify [<c0118072>] check_corruption+0x3/0x2d [ 1.060000] actual: 0f:1f:44:00:00 This warning shows that check_corruption+0x3 already had a nop in its place (0x0f1f440000). After compiling another kernel the problem went away. Later Eric Paris notice the same type of issue. Luckily, he saved the vmlinux file that caused it. In the file we found a bunch of duplicate mcount call site records, which lead us to the script. Perhaps this problem only happens to people named Eric. This patch changes the script to test if the __mcount_loc already exists in the object file, and if it does, it will print out an error message and kill the compile. Reported-by: Eric Sesterhenn <snakebyte@gmx.de> Reported-by: Eric Paris <eparis@redhat.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'scripts')
-rwxr-xr-xscripts/recordmcount.pl21
1 files changed, 18 insertions, 3 deletions
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index 2ded5c8e6b85..409596eca124 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -101,7 +101,7 @@ $P =~ s@.*/@@g;
101my $V = '0.1'; 101my $V = '0.1';
102 102
103if ($#ARGV < 7) { 103if ($#ARGV < 7) {
104 print "usage: $P arch objdump objcopy cc ld nm rm mv is_module inputfile\n"; 104 print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
105 print "version: $V\n"; 105 print "version: $V\n";
106 exit(1); 106 exit(1);
107} 107}
@@ -275,7 +275,6 @@ if (!$found_version) {
275 "\tDisabling local function references.\n"; 275 "\tDisabling local function references.\n";
276} 276}
277 277
278
279# 278#
280# Step 1: find all the local (static functions) and weak symbols. 279# Step 1: find all the local (static functions) and weak symbols.
281# 't' is local, 'w/W' is weak (we never use a weak function) 280# 't' is local, 'w/W' is weak (we never use a weak function)
@@ -343,13 +342,16 @@ sub update_funcs
343# 342#
344# Step 2: find the sections and mcount call sites 343# Step 2: find the sections and mcount call sites
345# 344#
346open(IN, "$objdump -dr $inputfile|") || die "error running $objdump"; 345open(IN, "$objdump -hdr $inputfile|") || die "error running $objdump";
347 346
348my $text; 347my $text;
349 348
349my $read_headers = 1;
350
350while (<IN>) { 351while (<IN>) {
351 # is it a section? 352 # is it a section?
352 if (/$section_regex/) { 353 if (/$section_regex/) {
354 $read_headers = 0;
353 355
354 # Only record text sections that we know are safe 356 # Only record text sections that we know are safe
355 if (defined($text_sections{$1})) { 357 if (defined($text_sections{$1})) {
@@ -383,6 +385,19 @@ while (<IN>) {
383 $ref_func = $text; 385 $ref_func = $text;
384 } 386 }
385 } 387 }
388 } elsif ($read_headers && /$mcount_section/) {
389 #
390 # Somehow the make process can execute this script on an
391 # object twice. If it does, we would duplicate the mcount
392 # section and it will cause the function tracer self test
393 # to fail. Check if the mcount section exists, and if it does,
394 # warn and exit.
395 #
396 print STDERR "ERROR: $mcount_section already in $inputfile\n" .
397 "\tThis may be an indication that your build is corrupted.\n" .
398 "\tDelete $inputfile and try again. If the same object file\n" .
399 "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
400 exit(-1);
386 } 401 }
387 402
388 # is this a call site to mcount? If so, record it to print later 403 # is this a call site to mcount? If so, record it to print later