aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorTony Breeds <tony@bakeyournoodle.com>2009-09-14 19:57:02 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-09-24 15:31:40 +1000
commit144ef909c09b60c97b3c20b69ea30abd1e60e54d (patch)
treebfade6f9d26ea4fddaf72e7c7f10102758fcacb6
parentad08587e5df17e192a57437bfedaba125998de25 (diff)
powerpc: Check for unsupported relocs when using CONFIG_RELOCATABLE
When using CONFIG_RELOCATABLE, we build the kernel as a position independent executable. The kernel then uses a little bit of relocation code to relocate itself. That code only deals with R_PPC64_RELATIVE relocations though. If for some reason you use assembly constructs such as LOAD_REG_IMMEDIATE() to load the address of a symbol, you'll generate different kinds of relocations that won't be processed properly and bad things will happen. (We have 2 such bugs today). The perl script tries to filter out "known" bad ones. It's possible that we are missing some in the case of a weak function that nobody implements, we'll see if we get false positive and fix it. Signed-off-by: Tony Breeds <tony@bakeyournoodle.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
-rw-r--r--arch/powerpc/Makefile11
-rwxr-xr-xarch/powerpc/relocs_check.pl56
2 files changed, 67 insertions, 0 deletions
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index aacf629c1a9f..1a54a3b3a3fa 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -164,6 +164,17 @@ PHONY += $(BOOT_TARGETS)
boot := arch/$(ARCH)/boot
+ifeq ($(CONFIG_RELOCATABLE),y)
+quiet_cmd_relocs_check = CALL $<
+ cmd_relocs_check = perl $< "$(OBJDUMP)" "$(obj)/vmlinux"
+
+PHONY += relocs_check
+relocs_check: arch/powerpc/relocs_check.pl vmlinux
+ $(call cmd,relocs_check)
+
+zImage: relocs_check
+endif
+
$(BOOT_TARGETS): vmlinux
$(Q)$(MAKE) ARCH=ppc64 $(build)=$(boot) $(patsubst %,$(boot)/%,$@)
diff --git a/arch/powerpc/relocs_check.pl b/arch/powerpc/relocs_check.pl
new file mode 100755
index 000000000000..d2571096c3e9
--- /dev/null
+++ b/arch/powerpc/relocs_check.pl
@@ -0,0 +1,56 @@
+#!/usr/bin/perl
+
+# Copyright © 2009 IBM Corporation
+
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version
+# 2 of the License, or (at your option) any later version.
+
+# This script checks the relcoations of a vmlinux for "suspicious"
+# relocations.
+
+use strict;
+use warnings;
+
+if ($#ARGV != 1) {
+ die "$0 [path to objdump] [path to vmlinux]\n";
+}
+
+# Have Kbuild supply the path to objdump so we handle cross compilation.
+my $objdump = shift;
+my $vmlinux = shift;
+my $bad_relocs_count = 0;
+my $bad_relocs = "";
+my $old_binutils = 0;
+
+open(FD, "$objdump -R $vmlinux|") or die;
+while (<FD>) {
+ study $_;
+
+ # Only look at relcoation lines.
+ next if (!/\s+R_/);
+
+ # These relocations are okay
+ next if (/R_PPC64_RELATIVE/ or /R_PPC64_NONE/ or
+ /R_PPC64_ADDR64\s+mach_/);
+
+ # If we see this type of relcoation it's an idication that
+ # we /may/ be using an old version of binutils.
+ if (/R_PPC64_UADDR64/) {
+ $old_binutils++;
+ }
+
+ $bad_relocs_count++;
+ $bad_relocs .= $_;
+}
+
+if ($bad_relocs_count) {
+ print "WARNING: $bad_relocs_count bad relocations\n";
+ print $bad_relocs;
+}
+
+if ($old_binutils) {
+ print "WARNING: You need at binutils >= 2.19 to build a ".
+ "CONFIG_RELCOATABLE kernel\n";
+}

Privacy Policy