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Date: Fri, 20 Nov 2009 00:23:13 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Heiko Carstens <heiko.carstens@...ibm.com>,
feng.tang@...el.com, Peter Zijlstra <peterz@...radead.org>,
Frederic Weisbecker <fweisbec@...il.com>,
David Daney <ddaney@...iumnetworks.com>,
Andrew Haley <aph@...hat.com>,
Richard Guenther <richard.guenther@...il.com>,
jakub@...hat.com, gcc <gcc@....gnu.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH][GIT PULL][v2.6.32] tracing/x86: Add check to detect GCC
messing with mcount prologue
Ingo,
Not sure if this is too much for this late in the -rc game, but it finds
the gcc bug at build time, and we don't need to disable function graph
tracer for all i386 builds.
This is built on my last urgent repo pull request.
Please pull the latest tip/tracing/urgent-2 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/tracing/urgent-2
Steven Rostedt (1):
tracing/x86: Add check to detect GCC messing with mcount prologue
----
kernel/trace/Kconfig | 1 -
scripts/Makefile.build | 25 +++++++++++++++-
scripts/recordmcount.pl | 74 +++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 95 insertions(+), 5 deletions(-)
---------------------------
commit c7715fb611c69ac4b7f722a891de08b206fb7686
Author: Steven Rostedt <srostedt@...hat.com>
Date: Thu Nov 19 23:41:02 2009 -0500
tracing/x86: Add check to detect GCC messing with mcount prologue
Latest versions of GCC create a funny prologue for some functions.
Instead of the typical:
push %ebp
mov %esp,%ebp
and $0xffffffe0,%esp
[...]
call mcount
GCC may try to align the stack before setting up the frame pointer
register:
push %edi
lea 0x8(%esp),%edi
and $0xffffffe0,%esp
pushl -0x4(%edi)
push %ebp
mov %esp,%ebp
[...]
call mcount
This crazy code places a copy of the return address into the
frame pointer. The function graph tracer uses this pointer to
save and replace the return address of the calling function to jump
to the function graph tracer's return handler, which will put back
the return address. But instead instead of the typical return:
mov %ebp,%esp
pop %ebp
ret
The return of the function performs:
lea -0x8(%edi),%esp
pop %edi
ret
The function graph tracer return handler will not be called at the exit
of the function, but the parent function will call it. Because we missed
the return of the child function, the handler will replace the parent's
return address with that of the child. Obviously this will cause a crash
(Note, there is code to detect this case and safely panic the kernel).
The kicker is that this happens to just a handful of functions.
And only with certain gcc options.
Compiling with: -march=pentium-mmx
will cause the problem to appear. But if you were to change
pentium-mmx to i686 or add -mtune=generic, then the problem goes away.
I first saw this problem when compiling with optimize for size.
But it seems that various other options may cause this issue to arise.
Instead of completely disabling the function graph tracer for i386 builds
this patch adds a check to recordmcount.pl to make sure that all
functions that contain a call to mcount start with "push %ebp".
If not, it will fail the compile and print out the nasty warning:
CC kernel/time/timer_stats.o
********************************************************
Your version of GCC breaks the function graph tracer
Please disable CONFIG_FUNCTION_GRAPH_TRACER
Failed function was "timer_stats_update_stats"
********************************************************
The script recordmcount.pl is given a new parameter "do_check". If
this is negative, the script will only perform this check without
creating the mcount caller section. This will be executed for x86_32
when CONFIG_FUNCTION_GRAPH_TRACER is enabled and CONFIG_DYNAMIC_FTRACE
is not.
If the arch is x86_32 and $do_check is greater than 1, it will perform
the check while processing the mcount callers. If $do_check is 0, then
no check will be performed. This is for non x86_32 archs and when
compiling without CONFIG_FUNCTION_GRAPH_TRACER enabled, even on x86_32.
Reported-by: Thomas Gleixner <tglx@...utronix.de>
LKML-Reference: <alpine.LFD.2.00.0911191423190.24119@...alhost.localdomain>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index b416512..cd39064 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -143,7 +143,6 @@ config FUNCTION_GRAPH_TRACER
bool "Kernel Function Graph Tracer"
depends on HAVE_FUNCTION_GRAPH_TRACER
depends on FUNCTION_TRACER
- depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
default y
help
Enable the kernel to trace a function at both its return
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 341b589..3b897f2 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -206,10 +206,33 @@ cmd_modversions = \
endif
ifdef CONFIG_FTRACE_MCOUNT_RECORD
+
+ ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ ifdef CONFIG_X86_32
+ rm_do_check = 1
+ else
+ rm_do_check = 0
+ endif
+ else
+ rm_do_check = 0
+ endif
+
cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
"$(if $(CONFIG_64BIT),64,32)" \
"$(OBJDUMP)" "$(OBJCOPY)" "$(CC)" "$(LD)" "$(NM)" "$(RM)" "$(MV)" \
- "$(if $(part-of-module),1,0)" "$(@)";
+ "$(if $(part-of-module),1,0)" "$(rm_do_check)" "$(@)";
+
+else
+
+ ifdef CONFIG_X86_32
+ ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
+ "$(if $(CONFIG_64BIT),64,32)" \
+ "$(OBJDUMP)" "$(OBJCOPY)" "$(CC)" "$(LD)" "$(NM)" "$(RM)" "$(MV)" \
+ "$(if $(part-of-module),1,0)" "-1" "$(@)";
+ endif
+ endif
+
endif
define rule_cc_o_c
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index 090d300..164a9d5 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -99,14 +99,14 @@ $P =~ s@.*/@@g;
my $V = '0.1';
-if ($#ARGV < 7) {
- print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module inputfile\n";
+if ($#ARGV < 11) {
+ print "usage: $P arch bits objdump objcopy cc ld nm rm mv is_module do_check inputfile\n";
print "version: $V\n";
exit(1);
}
my ($arch, $bits, $objdump, $objcopy, $cc,
- $ld, $nm, $rm, $mv, $is_module, $inputfile) = @ARGV;
+ $ld, $nm, $rm, $mv, $is_module, $do_check, $inputfile) = @ARGV;
# This file refers to mcount and shouldn't be ftraced, so lets' ignore it
if ($inputfile eq "kernel/trace/ftrace.o") {
@@ -129,6 +129,60 @@ $nm = "nm" if ((length $nm) == 0);
$rm = "rm" if ((length $rm) == 0);
$mv = "mv" if ((length $mv) == 0);
+# gcc can do stupid things with the stack pointer on x86_32.
+# It may pass a copy of the return address to mcount, which will
+# break the function graph tracer. If this happens then we need
+# to flag it and break the build.
+#
+# For x86_32, the parameter do_check will be negative if we only
+# want to perform the check, and positive if we should od the check.
+# If function graph tracing is not enabled, do_check will be zero.
+#
+
+my $check_next_line = 0;
+my $line_failed = 0;
+my $last_function;
+
+sub test_x86_32_prologue
+{
+ if ($check_next_line) {
+ if (!/push\s*\%ebp/) {
+ $line_failed = 1;
+ }
+ }
+
+ if ($line_failed && /mcount/) {
+ print STDERR "\n********************************************************\n";
+ print STDERR " Your version of GCC breaks the function graph tracer\n";
+ print STDERR " Please disable CONFIG_FUNCTION_GRAPH_TRACER\n";
+ print STDERR " Failed function was \"$last_function\"\n";
+ print STDERR "********************************************************\n\n";
+ exit -1;
+ }
+ $check_next_line = 0;
+
+ # check the first line after a function starts for
+ # push %ebp
+ if (/^[0-9a-fA-F]+\s+<([a-zA-Z_].*)>:$/) {
+ $last_function = $1;
+ $check_next_line = 1;
+ $line_failed = 0;
+ }
+}
+
+if ($do_check < 0) {
+ # Only perform the check and quit
+ open(IN, "$objdump -dr $inputfile|") || die "error running $objdump";
+
+ while (<IN>) {
+ test_x86_32_prologue;
+ }
+ close (IN);
+ exit 0;
+}
+
+my $check = 0;
+
#print STDERR "running: $P '$arch' '$objdump' '$objcopy' '$cc' '$ld' " .
# "'$nm' '$rm' '$mv' '$inputfile'\n";
@@ -153,6 +207,12 @@ if ($arch eq "x86") {
}
}
+if ($arch eq "i386") {
+ if ($do_check) {
+ $check = 1;
+ }
+}
+
#
# We base the defaults off of i386, the other archs may
# feel free to change them in the below if statements.
@@ -381,6 +441,14 @@ my $text;
my $read_headers = 1;
while (<IN>) {
+
+ # x86_32 may need to test the start of every function to see
+ # if GCC did not mess up the mcount prologue. All functions must
+ # start with push %ebp, otherwise it is broken.
+ if ($check) {
+ test_x86_32_prologue;
+ }
+
# is it a section?
if (/$section_regex/) {
$read_headers = 0;
--
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