purgatory: core purgatory functionality

Create a stand alone relocatable object purgatory which runs between two
kernels.  This name, concept and some code has been taken from
kexec-tools.  Idea is that this code runs after a crash and it runs in
minimal environment.  So keep it separate from rest of the kernel and in
long term we will have to practically do no maintenance of this code.

This code also has the logic to do verify sha256 hashes of various
segments which have been loaded into memory.  So first we verify that the
kernel we are jumping to is fine and has not been corrupted and make
progress only if checsums are verified.

This code also takes care of copying some memory contents to backup region.

[sfr@canb.auug.org.au: run host built programs from objtree]
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: WANG Chao <chaowang@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
new file mode 100644
index 000000000000..7fde9ee438a4
--- /dev/null
+++ b/arch/x86/purgatory/Makefile
@@ -0,0 +1,30 @@
+purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
+
+targets += $(purgatory-y)
+PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
+
+LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined -nostdlib -z nodefaultlib
+targets += purgatory.ro
+
+# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
+# in turn leaves some undefined symbols like __fentry__ in purgatory and not
+# sure how to relocate those. Like kexec-tools, use custom flags.
+
+KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -MD -Os -mcmodel=large
+
+$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
+		$(call if_changed,ld)
+
+targets += kexec-purgatory.c
+
+quiet_cmd_bin2c = BIN2C   $@
+      cmd_bin2c = cat $(obj)/purgatory.ro | $(objtree)/scripts/basic/bin2c kexec_purgatory > $(obj)/kexec-purgatory.c
+
+$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro FORCE
+	$(call if_changed,bin2c)
+
+
+# No loaders for 32bits yet.
+ifeq ($(CONFIG_X86_64),y)
+ obj-$(CONFIG_KEXEC)		+= kexec-purgatory.o
+endif