objtool: Add CONFIG_STACK_VALIDATION option

Add a CONFIG_STACK_VALIDATION option which will run "objtool check" for
each .o file to ensure the validity of its stack metadata.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/92baab69a6bf9bc7043af0bfca9fb964a1d45546.1456719558.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/Makefile b/Makefile
index fbe1b921798f9c985270ea95dfce7215f5abe8e9..62be03b2add449e5f15a86118c077dacbbf64e4a 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -993,7 +993,10 @@ prepare0: archprepare FORCE
        $(Q)$(MAKE) $(build)=.
 
 # All the preparing..
-prepare: prepare0
+prepare: prepare0 prepare-objtool
+
+PHONY += prepare-objtool
+prepare-objtool: $(if $(CONFIG_STACK_VALIDATION), tools/objtool FORCE)
 
 # Generate some files
 # ---------------------------------------------------------------------------

diff --git a/arch/Kconfig b/arch/Kconfig
index f6b649d88ec82ec44913d6a81ee0136498d88b92..81869a5e7e174ae470ba7746d88f8cdb35065c36 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -583,6 +583,12 @@ config HAVE_COPY_THREAD_TLS
          normal C parameter passing, rather than extracting the syscall
          argument from pt_regs.
 
+config HAVE_STACK_VALIDATION
+       bool
+       help
+         Architecture supports the 'objtool check' host tool command, which
+         performs compile-time stack metadata validation.
+
 #
 # ABI hall of shame
 #

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8bfd1aca7a3d01a9887700b3f90d1d5697a9dab4..855265621863d8503653fd6d7472511e5d64b8e2 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -342,6 +342,18 @@ config FRAME_POINTER
          larger and slower, but it gives very useful debugging information
          in case of kernel bugs. (precise oopses/stacktraces/warnings)
 
+config STACK_VALIDATION
+       bool "Compile-time stack metadata validation"
+       depends on HAVE_STACK_VALIDATION
+       default n
+       help
+         Add compile-time checks to validate stack metadata, including frame
+         pointers (if CONFIG_FRAME_POINTER is enabled).  This helps ensure
+         that runtime stack traces are more reliable.
+
+         For more information, see
+         tools/objtool/Documentation/stack-validation.txt.
+
 config DEBUG_FORCE_WEAK_PER_CPU
        bool "Force weak per-cpu definitions"
        depends on DEBUG_KERNEL

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2c47f9c305aae935ae6476108a16f15229d0081b..130a452d42eee515318f0c6a6ad65322c02c6a9a 100644 (file)
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -241,10 +241,32 @@ cmd_record_mcount =                                               \
        fi;
 endif
 
+ifdef CONFIG_STACK_VALIDATION
+
+__objtool_obj := $(objtree)/tools/objtool/objtool
+
+objtool_args = check
+ifndef CONFIG_FRAME_POINTER
+objtool_args += --no-fp
+endif
+
+# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
+# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
+# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
+cmd_objtool = $(if $(patsubst y%,, \
+       $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
+       $(__objtool_obj) $(objtool_args) "$(@)";)
+objtool_obj = $(if $(patsubst y%,, \
+       $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
+       $(__objtool_obj))
+
+endif # CONFIG_STACK_VALIDATION
+
 define rule_cc_o_c
        $(call echo-cmd,checksrc) $(cmd_checksrc)                         \
        $(call echo-cmd,cc_o_c) $(cmd_cc_o_c);                            \
        $(cmd_modversions)                                                \
+       $(cmd_objtool)                                            \
        $(call echo-cmd,record_mcount)                                    \
        $(cmd_record_mcount)                                              \
        scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' >    \
@@ -253,14 +275,23 @@ define rule_cc_o_c
        mv -f $(dot-target).tmp $(dot-target).cmd
 endef
 
+define rule_as_o_S
+       $(call echo-cmd,as_o_S) $(cmd_as_o_S);                            \
+       $(cmd_objtool)                                            \
+       scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,as_o_S)' >    \
+                                                     $(dot-target).tmp;  \
+       rm -f $(depfile);                                                 \
+       mv -f $(dot-target).tmp $(dot-target).cmd
+endef
+
 # Built-in and composite module parts
-$(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
+$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
        $(call cmd,force_checksrc)
        $(call if_changed_rule,cc_o_c)
 
 # Single-part modules are special since we need to mark them in $(MODVERDIR)
 
-$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
+$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
        $(call cmd,force_checksrc)
        $(call if_changed_rule,cc_o_c)
        @{ echo $(@:.o=.ko); echo $@; } > $(MODVERDIR)/$(@F:.o=.mod)
@@ -290,8 +321,8 @@ $(obj)/%.s: $(src)/%.S FORCE
 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 cmd_as_o_S       = $(CC) $(a_flags) -c -o $@ $<
 
-$(obj)/%.o: $(src)/%.S FORCE
-       $(call if_changed_dep,as_o_S)
+$(obj)/%.o: $(src)/%.S $(objtool_obj) FORCE
+       $(call if_changed_rule,as_o_S)
 
 targets += $(real-objs-y) $(real-objs-m) $(lib-y)
 targets += $(extra-y) $(MAKECMDGOALS) $(always)