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[Xen-changelog] [xen master] x86/xen_hello_world.xsplice: Test payload for patching 'xen_extra_version'.



commit ffcd7c069881219d4e60f3e5d7f12f1df44c9353
Author:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
AuthorDate: Wed Sep 16 10:37:12 2015 -0400
Commit:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CommitDate: Fri Apr 29 03:58:32 2016 -0400

    x86/xen_hello_world.xsplice: Test payload for patching 'xen_extra_version'.
    
    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@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Julien Grall <julien.grall@xxxxxxx> [ARM]
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 .gitignore                               |  2 ++
 docs/misc/xsplice.markdown               | 37 ++++++++++++++++++++++++++++
 xen/Makefile                             |  8 ++++--
 xen/arch/arm/Makefile                    |  3 +++
 xen/arch/x86/Makefile                    |  4 +++
 xen/arch/x86/test/Makefile               | 42 ++++++++++++++++++++++++++++++++
 xen/arch/x86/test/xen_hello_world.c      | 32 ++++++++++++++++++++++++
 xen/arch/x86/test/xen_hello_world_func.c | 22 +++++++++++++++++
 8 files changed, 148 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index 39eb779..4a81f43 100644
--- a/.gitignore
+++ b/.gitignore
@@ -246,6 +246,8 @@ 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
diff --git a/docs/misc/xsplice.markdown b/docs/misc/xsplice.markdown
index f5b150e..35ebc28 100644
--- a/docs/misc/xsplice.markdown
+++ b/docs/misc/xsplice.markdown
@@ -331,6 +331,43 @@ 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 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).
diff --git a/xen/Makefile b/xen/Makefile
index b483823..f49014b 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -39,8 +39,8 @@ dist: install
 
 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
@@ -76,6 +76,10 @@ _install: $(TARGET)$(CONFIG_XEN_INSTALL_SUFFIX)
                fi; \
        fi
 
+.PHONY: _tests
+_tests:
+       $(MAKE) -f $(BASEDIR)/Rules.mk -C arch/$(TARGET_ARCH) tests
+
 .PHONY: _uninstall
 _uninstall: D=$(DESTDIR)
 _uninstall: T=$(notdir $(TARGET))
diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index eae5cb3..f77f8db 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -57,6 +57,9 @@ ifeq ($(CONFIG_ARM_64),y)
        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
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index f74fd2c..f8f6eeb 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -76,6 +76,9 @@ $(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/'`
 
+.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)
 
@@ -179,3 +182,4 @@ 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
diff --git a/xen/arch/x86/test/Makefile b/xen/arch/x86/test/Makefile
new file mode 100644
index 0000000..8a05b33
--- /dev/null
+++ b/xen/arch/x86/test/Makefile
@@ -0,0 +1,42 @@
+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)
diff --git a/xen/arch/x86/test/xen_hello_world.c 
b/xen/arch/x86/test/xen_hello_world.c
new file mode 100644
index 0000000..f42b25c
--- /dev/null
+++ b/xen/arch/x86/test/xen_hello_world.c
@@ -0,0 +1,32 @@
+/*
+ * 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:
+ */
diff --git a/xen/arch/x86/test/xen_hello_world_func.c 
b/xen/arch/x86/test/xen_hello_world_func.c
new file mode 100644
index 0000000..1ad002a
--- /dev/null
+++ b/xen/arch/x86/test/xen_hello_world_func.c
@@ -0,0 +1,22 @@
+/*
+ * 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:
+ */
--
generated by git-patchbot for /home/xen/git/xen.git#master

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