This change demonstrates how to generate an xSplice ELF payload.
The idea here is that we want to patch in the hypervisor
the 'xen_version_extra' function with an function that will
return 'Hello World'. The 'xl info | grep extraversion'
will reflect the new value after the patching.
To generate this ELF payload file we need:
- C code of the new code (xen_hello_world_func.c).
- C code generating the .xsplice.funcs structure
(xen_hello_world.c)
- The address of the old code (xen_extra_version). We
retrieve it by using 'nm --defined' on xen-syms.
- The size of the new and old code for which we use
nm --defined -S on our code and xen-syms respectively.
There are two C files and one header files generated
during build. One could make this one C file if the
size of the newly patched function size was known in
advance (or an random value was choosen).
There is also a strict order of compiling:
1) xen_hello_world_func.c
2) config.h - extract the size of the new function,
the old function and the old function address.
3) xen_hello_world.c - which contains the .xsplice.funcs
structure.
4) Link the object files in an xen_hello_world.xsplice file.
The use-case is simple:
$xen-xsplice load /usr/lib/debug/xen_hello_world.xsplice
$xen-xsplice list
ID | status
----------------------------------------+------------
xen_hello_world APPLIED
$xl info | grep extra
xen_extra : Hello World
$xen-xsplice revert xen_hello_world
Performing revert: completed
$xen-xsplice unload xen_hello_world
Performing unload: completed
$xl info | grep extra
xen_extra : -unstable
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com> [ARM]
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
xen/arch/x86/efi/check.efi
xen/arch/x86/efi/disabled
xen/arch/x86/efi/mkreloc
+xen/arch/x86/test/config.h
+xen/arch/x86/test/xen_hello_world.xsplice
xen/arch/*/efi/boot.c
xen/arch/*/efi/compat.c
xen/arch/*/efi/efi.h
and the core code copies the data from the undo buffer (private internal copy)
to `old_addr`.
+### Example of .xsplice.funcs
+
+A simple example of what a payload file can be:
+
+<pre>
+/* MUST be in sync with hypervisor. */
+struct xsplice_patch_func {
+ const char *name;
+ void *new_addr;
+ void *old_addr;
+ uint32_t new_size;
+ uint32_t old_size;
+ uint8_t version;
+ uint8_t pad[31];
+};
+
+/* Our replacement function for xen_extra_version. */
+const char *xen_hello_world(void)
+{
+ return "Hello World";
+}
+
+static unsigned char patch_this_fnc[] = "xen_extra_version";
+
+struct xsplice_patch_func xsplice_hello_world = {
+ .version = XSPLICE_PAYLOAD_VERSION,
+ .name = patch_this_fnc,
+ .new_addr = xen_hello_world,
+ .old_addr = (void *)0xffff82d08013963c, /* Extracted from xen-syms. */
+ .new_size = 13, /* To be be computed by scripts. */
+ .old_size = 13, /* -----------""--------------- */
+} __attribute__((__section__(".xsplice.funcs")));
+
+</pre>
+
+Code must be compiled with -fPIC.
+
## Hypercalls
We will employ the sub operations of the system management hypercall (sysctl).
build install:: include/config/auto.conf
-.PHONY: build install uninstall clean distclean cscope TAGS tags MAP gtags
-build install uninstall debug clean distclean cscope TAGS tags MAP gtags::
+.PHONY: build install uninstall clean distclean cscope TAGS tags MAP gtags tests
+build install uninstall debug clean distclean cscope TAGS tags MAP gtags tests::
ifneq ($(XEN_TARGET_ARCH),x86_32)
$(MAKE) -f Rules.mk _$@
else
fi; \
fi
+.PHONY: _tests
+_tests:
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C arch/$(TARGET_ARCH) tests
+
.PHONY: _uninstall
_uninstall: D=$(DESTDIR)
_uninstall: T=$(notdir $(TARGET))
ln -sf $(notdir $@) ../../$(notdir $@).efi
endif
+.PHONY: tests
+tests:
+
$(TARGET).axf: $(TARGET)-syms
# XXX: VE model loads by VMA so instead of
# making a proper ELF we link with LMA == VMA and adjust crudely
./boot/mkelf32 $(TARGET)-syms $(TARGET) 0x100000 \
`$(NM) -nr $(TARGET)-syms | head -n 1 | sed -e 's/^\([^ ]*\).*/0x\1/'`
+.PHONY: tests
+tests:
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C test xsplice
ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o $(BASEDIR)/arch/x86/efi/built_in.o $(ALL_OBJS)
rm -f $(BASEDIR)/.xen-syms.[0-9]* boot/.*.d
rm -f $(BASEDIR)/.xen.efi.[0-9]* efi/*.o efi/.*.d efi/*.efi efi/disabled efi/mkreloc
rm -f boot/reloc.S boot/reloc.lnk boot/reloc.bin
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C test clean
--- /dev/null
+include $(XEN_ROOT)/Config.mk
+
+CODE_ADDR=$(shell nm --defined $(1) | grep $(2) | awk '{print "0x"$$1}')
+CODE_SZ=$(shell nm --defined -S $(1) | grep $(2) | awk '{ print "0x"$$2}')
+
+.PHONY: default
+
+XSPLICE := xen_hello_world.xsplice
+
+default: xsplice
+
+install: xsplice
+ $(INSTALL_DATA) $(XSPLICE) $(DESTDIR)$(DEBUG_DIR)/$(XSPLICE)
+uninstall:
+ rm -f $(DESTDIR)$(DEBUG_DIR)/$(XSPLICE)
+
+.PHONY: clean
+clean::
+ rm -f *.o .*.o.d *.xsplice config.h
+
+#
+# To compute these values we need the binary files: xen-syms
+# and xen_hello_world_func.o to be already compiled.
+#
+.PHONY: config.h
+config.h: OLD_CODE=$(call CODE_ADDR,$(BASEDIR)/xen-syms,xen_extra_version)
+config.h: OLD_CODE_SZ=$(call CODE_SZ,$(BASEDIR)/xen-syms,xen_extra_version)
+config.h: NEW_CODE_SZ=$(call CODE_SZ,$<,xen_hello_world)
+config.h: xen_hello_world_func.o
+ (set -e; \
+ echo "#define NEW_CODE_SZ $(NEW_CODE_SZ)"; \
+ echo "#define OLD_CODE_SZ $(OLD_CODE_SZ)"; \
+ echo "#define OLD_CODE $(OLD_CODE)") > $@
+
+xen_hello_world.o: config.h
+
+.PHONY: $(XSPLICE)
+$(XSPLICE): xen_hello_world_func.o xen_hello_world.o
+ $(LD) $(LDFLAGS) -r -o $(XSPLICE) $^
+
+.PHONY: xsplice
+xsplice: $(XSPLICE)
--- /dev/null
+/*
+ * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ */
+
+#include "config.h"
+#include <xen/types.h>
+#include <xen/xsplice.h>
+
+#include <public/sysctl.h>
+
+static char hello_world_patch_this_fnc[] = "xen_extra_version";
+extern const char *xen_hello_world(void);
+
+struct xsplice_patch_func __section(".xsplice.funcs") xsplice_xen_hello_world = {
+ .version = XSPLICE_PAYLOAD_VERSION,
+ .name = hello_world_patch_this_fnc,
+ .new_addr = xen_hello_world,
+ .old_addr = (void *)OLD_CODE,
+ .new_size = NEW_CODE_SZ,
+ .old_size = OLD_CODE_SZ,
+};
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
--- /dev/null
+/*
+ * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ */
+
+#include <xen/types.h>
+
+/* Our replacement function for xen_extra_version. */
+const char *xen_hello_world(void)
+{
+ return "Hello World";
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
projects / xen.git / commitdiff