Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 144ef909 authored by Tony Breeds's avatar Tony Breeds Committed by Benjamin Herrenschmidt
Browse files

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: default avatarTony Breeds <tony@bakeyournoodle.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent ad08587e

arch/powerpc/Makefile

+11 −0
Original line number Diff line number Diff line
@@ -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)/%,$@)

arch/powerpc/relocs_check.pl

0 → 100755
+56 −0
Original line number Diff line number Diff line 
#!/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";

}