Re: [Xen-devel] [PATCH v2 08/12] livepatch: Add support for inline asm hotpatching expectations

[Konrad Rzeszutek Wilk <konrad@darnok.org>]

> diff --git a/xen/test/livepatch/Makefile b/xen/test/livepatch/Makefile
> index 23113d3418..067861903f 100644
> --- a/xen/test/livepatch/Makefile
> +++ b/xen/test/livepatch/Makefile
> @@ -27,6 +27,8 @@ LIVEPATCH_ACTION_HOOKS_NOFUNC := xen_action_hooks_nofunc.livepatch
>  LIVEPATCH_ACTION_HOOKS_MARKER:= xen_action_hooks_marker.livepatch
>  LIVEPATCH_ACTION_HOOKS_NOAPPLY:= xen_action_hooks_noapply.livepatch
>  LIVEPATCH_ACTION_HOOKS_NOREVERT:= xen_action_hooks_norevert.livepatch
> +LIVEPATCH_EXPECTATIONS:= xen_expectations.livepatch
> +LIVEPATCH_EXPECTATIONS_FAIL:= xen_expectations_fail.livepatch
>  
>  LIVEPATCHES += $(LIVEPATCH)
>  LIVEPATCHES += $(LIVEPATCH_BYE)
> @@ -40,6 +42,8 @@ LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_NOFUNC)
>  LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_MARKER)
>  LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_NOAPPLY)
>  LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_NOREVERT)
> +LIVEPATCHES += $(LIVEPATCH_EXPECTATIONS)
> +LIVEPATCHES += $(LIVEPATCH_EXPECTATIONS_FAIL)
>  
>  LIVEPATCH_DEBUG_DIR ?= $(DEBUG_DIR)/xen-livepatch
>  
> @@ -54,7 +58,7 @@ uninstall:
>  
>  .PHONY: clean
>  clean::
> -	rm -f *.o .*.o.d *.livepatch config.h
> +	rm -f *.o .*.o.d *.livepatch config.h expect_config.h
>  
>  #
>  # To compute these values we need the binary files: xen-syms
> @@ -182,8 +186,27 @@ xen_actions_hooks_norevert.o: config.h
>  $(LIVEPATCH_ACTION_HOOKS_NOREVERT): xen_action_hooks_marker.o xen_hello_world_func.o note.o xen_note.o
>  	$(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_ACTION_HOOKS_NOREVERT) $^
>  
> +CODE_GET_EXPECT=$(shell objdump -d --insn-width=1 $(1) | grep -A6 -E '<'$(2)'>:' | tail -n +2 | awk 'BEGIN {printf "{"} {printf "0x%s,", $$2}' | sed 's/,$$/}/g')
> +.PHONY: expect_config.h
> +expect_config.h: EXPECT_BYTES=$(call CODE_GET_EXPECT,$(BASEDIR)/xen-syms,xen_extra_version)
> +expect_config.h: EXPECT_BYTES_COUNT=6
> +expect_config.h: xen_expectations.o
> +	(set -e; \
> +	 echo "#define EXPECT_BYTES $(EXPECT_BYTES)"; \
> +         echo "#define EXPECT_BYTES_COUNT $(EXPECT_BYTES_COUNT)") > $@
> +
> +xen_expectations.o: expect_config.h
> +
> +.PHONY: $(LIVEPATCH_EXPECTATIONS)
> +$(LIVEPATCH_EXPECTATIONS): xen_expectations.o xen_hello_world_func.o note.o xen_note.o
> +	$(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_EXPECTATIONS) $^
> +
> +.PHONY: $(LIVEPATCH_EXPECTATIONS_FAIL)
> +$(LIVEPATCH_EXPECTATIONS_FAIL): xen_expectations_fail.o xen_hello_world_func.o note.o xen_note.o
> +	$(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_EXPECTATIONS_FAIL) $^
> +
>  .PHONY: livepatch
>  livepatch: $(LIVEPATCH) $(LIVEPATCH_BYE) $(LIVEPATCH_REPLACE) $(LIVEPATCH_NOP) $(LIVEPATCH_NO_XEN_BUILDID) \
>             $(LIVEPATCH_PREPOST_HOOKS) $(LIVEPATCH_PREPOST_HOOKS_FAIL) $(LIVEPATCH_ACTION_HOOKS) \
>             $(LIVEPATCH_ACTION_HOOKS_NOFUNC) $(LIVEPATCH_ACTION_HOOKS_MARKER) $(LIVEPATCH_ACTION_HOOKS_NOAPPLY) \
> -           $(LIVEPATCH_ACTION_HOOKS_NOREVERT)
> +           $(LIVEPATCH_ACTION_HOOKS_NOREVERT) $(LIVEPATCH_EXPECTATIONS) $(LIVEPATCH_EXPECTATIONS_FAIL)
> diff --git a/xen/test/livepatch/xen_expectations.c b/xen/test/livepatch/xen_expectations.c
> new file mode 100644
> index 0000000000..c8175a458b
> --- /dev/null
> +++ b/xen/test/livepatch/xen_expectations.c
> @@ -0,0 +1,41 @@
> +/*
> + * Copyright (c) 2019 Amazon.com, Inc. or its affiliates. All rights reserved.
> + *
> + */
> +
> +#include "expect_config.h"
> +#include <xen/lib.h>
> +#include <xen/types.h>
> +#include <xen/version.h>
> +#include <xen/livepatch.h>
> +#include <xen/livepatch_payload.h>
> +
> +#include <public/sysctl.h>
> +
> +static const char livepatch_exceptions_str[] = "xen_extra_version";
> +extern const char *xen_hello_world(void);
> +
> +struct livepatch_func __section(".livepatch.funcs") livepatch_exceptions = {
> +    .version = LIVEPATCH_PAYLOAD_VERSION,
> +    .name = livepatch_exceptions_str,
> +    .new_addr = xen_hello_world,
> +    .old_addr = xen_extra_version,
> +    .new_size = EXPECT_BYTES_COUNT,
> +    .old_size = EXPECT_BYTES_COUNT,
> +    .expect = {
> +        .enabled = 1,
> +        .len = EXPECT_BYTES_COUNT,
> +        .data = EXPECT_BYTES
> +    },
> +
> +};

When I compile with 32-bit ARM 'make tests' I get:

arm-eabi-ld    -EL -EL     --build-id=sha1 -r -o xen_action_hooks_norevert.livepatch xen_action_hooks_marker.o xen_hello_world_func.o note.o xen_note.o
make[3]: Circular expect_config.h <- xen_expectations.o dependency dropped.
objdump: can't disassemble for architecture UNKNOWN!

(set -e; \
 echo "#define EXPECT_BYTES {"; \
         echo "#define EXPECT_BYTES_COUNT 6") > expect_config.h
arm-eabi-gcc -marm -DBUILD_ID -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement -Wno-unused-but-set-variable -Wno-unused-local-typedefs   -O1 -fno-omit-frame-pointer -nostdinc -fno-builtin -fno-common -Werror -Wredundant-decls -Wno-pointer-arith -Wvla -pipe -D__XEN__ -include /home/konrad/A20/xen.git/xen/include/xen/config.h '-D__OBJECT_FILE__="xen_expectations.o"' -Wa,--strip-local-absolute -g -MMD -MF ./.xen_expectations.o.d -msoft-float -mcpu=cortex-a15 -DCONFIG_EARLY_PRINTK -DEARLY_PRINTK_INC=\"debug-8250.inc\" -DEARLY_PRINTK_BAUD= -DEARLY_UART_BASE_ADDRESS=0x01c28000 -DEARLY_UART_REG_SHIFT=2  -I/home/konrad/A20/xen.git/xen/include -fno-stack-protector -fno-exceptions -Wnested-externs -DGCC_HAS_VISIBILITY_ATTRIBUTE -marm -DBUILD_ID -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wdeclaration-after-statement -Wno-unused-but-set-variable -Wno-unused-local-typedefs   -c xen_expectations.c -o xen_expectations.o
xen_expectations.c:31:2: error: expected '}' before ';' token
 };
  ^
xen_expectations.c:18:76: note: to match this '{'
 struct livepatch_func __section(".livepatch.funcs") livepatch_exceptions = {
                                                                            ^
make[3]: *** [/home/konrad/A20/xen.git/xen/Rules.mk:202: xen_expectations.o] Error 1
make[3]: Leaving directory '/home/konrad/A20/xen.git/xen/test/livepatch'


And this is what expect_config.h looks like:

#define EXPECT_BYTES {
#define EXPECT_BYTES_COUNT 6

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