@@ -245,6 +245,8 @@ xen/arch/x86/efi.lds
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
@@ -321,11 +321,47 @@ size.
When applying the patch the hypervisor iterates over each `xsplice_patch_func`
structure and the core code inserts a trampoline at `old_addr` to `new_addr`.
+The `new_addr` is altered when the ELF payload is loaded.
When reverting a patch, the hypervisor iterates over each `xsplice_patch_func`
and the core code copies the data from the undo buffer (private internal copy)
to `old_addr`.
+### Example
+
+A simple example of what a payload file can be:
+
+<pre>
+/* MUST be in sync with hypervisor. */
+struct xsplice_patch_func {
+ const char *name;
+ uint64_t new_addr;
+ uint64_t old_addr;
+ uint32_t new_size;
+ uint32_t old_size;
+ uint8_t pad[32];
+};
+
+/* Our replacement function for xen_extra_version. */
+const char *xen_hello_world(void)
+{
+ return "Hello World";
+}
+
+static unsigned char name[] = "xen_hello_world";
+
+struct xsplice_patch_func xsplice_hello_world = {
+ .name = name,
+ .new_addr = (unsigned long)(xen_hello_world),
+ .old_addr = 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).
@@ -75,6 +75,7 @@ _install: $(TARGET)$(CONFIG_XEN_INSTALL_SUFFIX)
echo 'EFI installation only partially done (EFI_VENDOR not set)' >&2; \
fi; \
fi
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C arch/$(TARGET_ARCH) install
.PHONY: _uninstall
_uninstall: D=$(DESTDIR)
@@ -92,6 +93,7 @@ _uninstall:
rm -f $(D)$(EFI_DIR)/$(T)-$(XEN_VERSION).efi
rm -f $(D)$(EFI_DIR)/$(T).efi
rm -f $(D)$(EFI_MOUNTPOINT)/efi/$(EFI_VENDOR)/$(T)-$(XEN_FULLVERSION).efi
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C arch/$(TARGET_ARCH) uninstall
.PHONY: _debug
_debug:
@@ -57,6 +57,10 @@ ifeq ($(CONFIG_ARM_64),y)
ln -sf $(notdir $@) ../../$(notdir $@).efi
endif
+install:
+
+uninstall:
+
$(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
@@ -74,7 +74,12 @@ efi-y := $(shell if [ ! -r $(BASEDIR)/include/xen/compile.h -o \
$(TARGET): $(TARGET)-syms $(efi-y) boot/mkelf32
./boot/mkelf32 $(TARGET)-syms $(TARGET) 0x100000 \
`$(NM) -nr $(TARGET)-syms | head -n 1 | sed -e 's/^\([^ ]*\).*/0x\1/'`
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C test
+install:
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C test install
+uninstall:
+ $(MAKE) -f $(BASEDIR)/Rules.mk -C test uninstall
ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o $(BASEDIR)/arch/x86/efi/built_in.o $(ALL_OBJS)
@@ -178,3 +183,4 @@ clean::
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
new file mode 100644
@@ -0,0 +1,50 @@
+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
+ifdef CONFIG_XSPLICE
+
+XSPLICE := xen_hello_world.xsplice
+
+default: xsplice
+
+install: xsplice
+ $(INSTALL_DATA) $(XSPLICE) $(DESTDIR)$(DEBUG_DIR)/$(XSPLICE)
+uninstall:
+ rm -f $(DESTDIR)$(DEBUG_DIR)/$(XSPLICE)
+else
+default:
+install:
+uninstall:
+endif
+
+.PHONY: clean
+clean::
+ rm -f *.o .*.o.d $(XSPLICE) config.h
+
+#
+# To compute these values we need the binary files: xen-syms
+# and xen_hello_world_func.o to be already compiled.
+#
+# We can be assured that xen-syms is already built as we are
+# the last entry in the build target.
+#
+.PHONY: config.h
+config.h: OLD_CODE=$(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)") > $@
+
+.PHONY: xsplice
+xsplice: config.h
+ # Need to have these done in sequential order
+ $(MAKE) -f $(BASEDIR)/Rules.mk xen_hello_world_func.o
+ $(MAKE) -f $(BASEDIR)/Rules.mk xen_hello_world.o
+ $(LD) $(LDFLAGS) -r -o $(XSPLICE) xen_hello_world_func.o xen_hello_world.o
+
new file mode 100644
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ */
+
+#include <xen/config.h>
+#include <xen/types.h>
+#include <xen/xsplice.h>
+#include "config.h"
+
+static char xen_hello_world_name[] = "xen_hello_world";
+extern const char *xen_hello_world(void);
+
+struct xsplice_patch_func __section(".xsplice.funcs") xsplice_xen_hello_world = {
+ .name = xen_hello_world_name,
+ .new_addr = (unsigned long)(xen_hello_world),
+ .old_addr = 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:
+ */
new file mode 100644
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ */
+
+#include <xen/config.h>
+#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:
+ */
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> --- Cc: Stefano Stabellini <stefano.stabellini@citrix.com> Cc: Julien Grall <julien.grall@arm.com> Cc: Keir Fraser <keir@xen.org> Cc: Jan Beulich <jbeulich@suse.com> Cc: Andrew Cooper <andrew.cooper3@citrix.com> v2: Do it using hypervisor Makefiles v3: Remove the stale linker file. v4: Add Copyright and local definition block v5: s/name/xen_hello_world_name/ --- .gitignore | 2 ++ docs/misc/xsplice.markdown | 36 +++++++++++++++++++++++ xen/Makefile | 2 ++ xen/arch/arm/Makefile | 4 +++ xen/arch/x86/Makefile | 6 ++++ xen/arch/x86/test/Makefile | 50 ++++++++++++++++++++++++++++++++ xen/arch/x86/test/xen_hello_world.c | 30 +++++++++++++++++++ xen/arch/x86/test/xen_hello_world_func.c | 23 +++++++++++++++ 8 files changed, 153 insertions(+) create mode 100644 xen/arch/x86/test/Makefile create mode 100644 xen/arch/x86/test/xen_hello_world.c create mode 100644 xen/arch/x86/test/xen_hello_world_func.c