From 81ecb38b83b0e9e11d9baecaa36458edc44a3edb Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 28 Nov 2019 17:47:25 +0100 Subject: [PATCH] build: provide option to disambiguate symbol names MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The .file assembler directives generated by the compiler do not include any path components (gcc) or just the ones specified on the command line (clang, at least version 5), and hence multiple identically named source files (in different directories) may produce identically named static symbols (in their kallsyms representation). The binary diffing algorithm used by xen-livepatch, however, depends on having unique symbols. Make the ENFORCE_UNIQUE_SYMBOLS Kconfig option control the (build) behavior, and if enabled use objcopy to prepend the (relative to the xen/ subdirectory) path to the compiler invoked STT_FILE symbols. Note that this build option is made no longer depend on LIVEPATCH, but merely defaults to its setting now. Conditionalize explicit .file directive insertion in C files where it exists just to disambiguate names in a less generic manner; note that at the same time the redundant emission of STT_FILE symbols gets suppressed for clang. Assembler files as well as multiply compiled C ones using __OBJECT_FILE__ are left alone for the time being. Since we now expect there not to be any duplicates anymore, also don't force the selection of the option to 'n' anymore in allrandom.config. Similarly COVERAGE no longer suppresses duplicate symbol warnings if enforcement is in effect, which in turn allows SUPPRESS_DUPLICATE_SYMBOL_WARNINGS to simply depend on !ENFORCE_UNIQUE_SYMBOLS. Signed-off-by: Jan Beulich Acked-by: Konrad Rzeszutek Wilk Acked-by: Wei Liu Reviewed-by: Roger Pau Monné Tested-by: Sergey Dyasli Acked-by: Andrew Cooper --- xen/Kconfig.debug | 2 +- xen/Rules.mk | 14 +++++++++++++- xen/arch/x86/x86_64/compat.c | 2 +- xen/arch/x86/x86_64/mm.c | 2 +- xen/arch/x86/x86_64/physdev.c | 2 +- xen/arch/x86/x86_64/platform_hypercall.c | 2 +- xen/common/Kconfig | 7 +++---- xen/common/compat/domain.c | 2 +- xen/common/compat/kernel.c | 2 +- xen/common/compat/memory.c | 2 +- xen/common/compat/multicall.c | 2 +- xen/include/xen/config.h | 8 ++++++++ xen/tools/kconfig/allrandom.config | 1 - 13 files changed, 33 insertions(+), 15 deletions(-) diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug index 22573e74db..cf42e5e7a0 100644 --- a/xen/Kconfig.debug +++ b/xen/Kconfig.debug @@ -38,7 +38,7 @@ config FRAME_POINTER config COVERAGE bool "Code coverage support" depends on !LIVEPATCH - select SUPPRESS_DUPLICATE_SYMBOL_WARNINGS + select SUPPRESS_DUPLICATE_SYMBOL_WARNINGS if !ENFORCE_UNIQUE_SYMBOLS ---help--- Enable code coverage support. diff --git a/xen/Rules.mk b/xen/Rules.mk index 3090ea7828..b0bc7601c1 100644 --- a/xen/Rules.mk +++ b/xen/Rules.mk @@ -194,12 +194,24 @@ FORCE: .PHONY: clean clean:: $(addprefix _clean_, $(subdir-all)) - rm -f *.o *~ core $(DEPS_RM) + rm -f *.o .*.o.tmp *~ core $(DEPS_RM) _clean_%/: FORCE $(MAKE) -f $(BASEDIR)/Rules.mk -C $* clean +SRCPATH := $(patsubst $(BASEDIR)/%,%,$(CURDIR)) + %.o: %.c Makefile +ifeq ($(CONFIG_ENFORCE_UNIQUE_SYMBOLS),y) + $(CC) $(CFLAGS) -c $< -o $(@D)/.$(@F).tmp +ifeq ($(clang),y) + $(OBJCOPY) --redefine-sym $<=$(SRCPATH)/$< $(@D)/.$(@F).tmp $@ +else + $(OBJCOPY) --redefine-sym $( #include diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c index fa55f3474e..8ea09ecc30 100644 --- a/xen/arch/x86/x86_64/mm.c +++ b/xen/arch/x86/x86_64/mm.c @@ -16,7 +16,7 @@ * with this program; If not, see . */ -asm(".file \"" __FILE__ "\""); +EMIT_FILE; #include #include diff --git a/xen/arch/x86/x86_64/physdev.c b/xen/arch/x86/x86_64/physdev.c index c5a00ea93f..0a50cbd4d8 100644 --- a/xen/arch/x86/x86_64/physdev.c +++ b/xen/arch/x86/x86_64/physdev.c @@ -2,7 +2,7 @@ * physdev.c */ -asm(".file \"" __FILE__ "\""); +EMIT_FILE; #include #include diff --git a/xen/arch/x86/x86_64/platform_hypercall.c b/xen/arch/x86/x86_64/platform_hypercall.c index 8fa2543a2d..fbba893a47 100644 --- a/xen/arch/x86/x86_64/platform_hypercall.c +++ b/xen/arch/x86/x86_64/platform_hypercall.c @@ -2,7 +2,7 @@ * platform_hypercall.c */ -asm(".file \"" __FILE__ "\""); +EMIT_FILE; #include #include diff --git a/xen/common/Kconfig b/xen/common/Kconfig index f754741972..2f516da101 100644 --- a/xen/common/Kconfig +++ b/xen/common/Kconfig @@ -373,8 +373,7 @@ config FAST_SYMBOL_LOOKUP config ENFORCE_UNIQUE_SYMBOLS bool "Enforce unique symbols" - default y - depends on LIVEPATCH + default LIVEPATCH ---help--- Multiple symbols with the same name aren't generally a problem unless livepatching is to be used. @@ -387,8 +386,8 @@ config ENFORCE_UNIQUE_SYMBOLS livepatch build and apply correctly. config SUPPRESS_DUPLICATE_SYMBOL_WARNINGS - bool "Suppress duplicate symbol warnings" if !ENFORCE_UNIQUE_SYMBOLS - default y if !ENFORCE_UNIQUE_SYMBOLS + bool "Suppress duplicate symbol warnings" + depends on !ENFORCE_UNIQUE_SYMBOLS ---help--- Multiple symbols with the same name aren't generally a problem unless Live patching is to be used, so these warnings can be diff --git a/xen/common/compat/domain.c b/xen/common/compat/domain.c index 2531fa7421..11c6afc463 100644 --- a/xen/common/compat/domain.c +++ b/xen/common/compat/domain.c @@ -3,7 +3,7 @@ * */ -asm(".file \"" __FILE__ "\""); +EMIT_FILE; #include #include diff --git a/xen/common/compat/kernel.c b/xen/common/compat/kernel.c index 64232669d2..5c6e7322f8 100644 --- a/xen/common/compat/kernel.c +++ b/xen/common/compat/kernel.c @@ -2,7 +2,7 @@ * kernel.c */ -asm(".file \"" __FILE__ "\""); +EMIT_FILE; #include #include diff --git a/xen/common/compat/memory.c b/xen/common/compat/memory.c index 10a954f281..3851f756c7 100644 --- a/xen/common/compat/memory.c +++ b/xen/common/compat/memory.c @@ -1,4 +1,4 @@ -asm(".file \"" __FILE__ "\""); +EMIT_FILE; #include #include diff --git a/xen/common/compat/multicall.c b/xen/common/compat/multicall.c index 43d2d8152d..a0e9918f48 100644 --- a/xen/common/compat/multicall.c +++ b/xen/common/compat/multicall.c @@ -2,7 +2,7 @@ * multicall.c */ -asm(".file \"" __FILE__ "\""); +EMIT_FILE; #include #include diff --git a/xen/include/xen/config.h b/xen/include/xen/config.h index a106380a23..b76222ecf6 100644 --- a/xen/include/xen/config.h +++ b/xen/include/xen/config.h @@ -11,7 +11,15 @@ #ifndef __ASSEMBLY__ #include + +#if defined(CONFIG_ENFORCE_UNIQUE_SYMBOLS) || defined(__clang__) +# define EMIT_FILE asm ( "" ) +#else +# define EMIT_FILE asm ( ".file \"" __FILE__ "\"" ) +#endif + #endif + #include #define EXPORT_SYMBOL(var) diff --git a/xen/tools/kconfig/allrandom.config b/xen/tools/kconfig/allrandom.config index c480896b96..76f74320b5 100644 --- a/xen/tools/kconfig/allrandom.config +++ b/xen/tools/kconfig/allrandom.config @@ -2,4 +2,3 @@ CONFIG_GCOV_FORMAT_AUTODETECT=y CONFIG_UBSAN=n -CONFIG_ENFORCE_UNIQUE_SYMBOLS=n -- 2.30.2