From: Kevin Brodsky <[email protected]> Expose the new compat vDSO via the COMPAT_VDSO config option.
The option is not enabled in defconfig because we really need a 32-bit compiler this time, and we rely on the user to provide it themselves by setting CROSS_COMPILE_ARM32. Therefore enabling the option by default would make little sense, since the user must explicitly set a non-standard environment variable anyway. CONFIG_COMPAT_VDSO is not directly used in the code, because we want to ignore it (build as if it were not set) if the user didn't set CROSS_COMPILE_ARM32. If the variable has been set to a valid prefix, CONFIG_VDSO32 will be set; this is the option that the code and Makefiles test. For more flexibility, like CROSS_COMPILE, CROSS_COMPILE_ARM32 can also be set via CONFIG_CROSS_COMPILE_ARM32 (the environment variable overrides the config option, as expected). Signed-off-by: Kevin Brodsky <[email protected]> Signed-off-by: Mark Salyzyn <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Will Deacon <[email protected]> Cc: Dave Martin <[email protected]> Cc: "Eric W. Biederman" <[email protected]> Cc: [email protected] Cc: [email protected] --- arch/arm64/Kconfig | 24 ++++++++++++++++++++++++ arch/arm64/Makefile | 35 +++++++++++++++++++++++++++++++++-- arch/arm64/kernel/Makefile | 3 +++ 3 files changed, 60 insertions(+), 2 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index d8a4fda50477..379d0154b363 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1183,6 +1183,30 @@ config SYSVIPC_COMPAT def_bool y depends on COMPAT && SYSVIPC +config COMPAT_VDSO + bool "32-bit vDSO" + depends on COMPAT + default n + help + Warning: a 32-bit toolchain is necessary to build the vDSO. You + must explicitly define which toolchain should be used by setting + CROSS_COMPILE_ARM32 to the prefix of the 32-bit toolchain (same format + as CROSS_COMPILE). If CROSS_COMPILE_ARM32 is empty, a warning will be + printed and the kernel will be built as if COMPAT_VDSO had not been + set. If CROSS_COMPILE_ARM32 is set to an invalid prefix, compilation + will be aborted. + + Provide a vDSO to 32-bit processes. It includes the symbols provided + by the vDSO from the 32-bit kernel, so that a 32-bit libc can use + the compat vDSO without modification. It also provides sigreturn + trampolines, replacing the sigreturn page. + +config CROSS_COMPILE_ARM32 + string "32-bit toolchain prefix" + help + Same as setting CROSS_COMPILE_ARM32 in the environment, but saved for + future builds. The environment variable overrides this config option. + endmenu menu "Power management options" diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 939b310913cf..baf36f0a992d 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -45,10 +45,39 @@ $(warning Detected assembler with broken .inst; disassembly will be unreliable) endif endif -KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) +ifeq ($(CONFIG_COMPAT_VDSO), y) + CROSS_COMPILE_ARM32 ?= $(CONFIG_CROSS_COMPILE_ARM32:"%"=%) + + # Check that the user has provided a valid prefix for the 32-bit toolchain. + # To prevent selecting the system $(cc-name) by default, the prefix is not + # allowed to be empty, unlike CROSS_COMPILE. In the unlikely event that the + # system $(cc-name) is actually the 32-bit ARM compiler to be used, the + # variable can be set to the dirname (e.g. CROSS_COMPILE_ARM32=/usr/bin/). + # Note: this Makefile is read both before and after regenerating the config + # (if needed). Any warning appearing before the config has been regenerated + # should be ignored. If the error is triggered and you set + # CONFIG_CROSS_COMPILE_ARM32, set CROSS_COMPILE_ARM32 to an appropriate value + # when invoking make and fix CONFIG_CROSS_COMPILE_ARM32. + ifeq ($(CROSS_COMPILE_ARM32),) + $(error CROSS_COMPILE_ARM32 not defined or empty, the compat vDSO will not be built) + else ifeq ($(cc-name),clang) + export CLANG_TRIPLE_ARM32 ?= $(CROSS_COMPILE_ARM32) + export CLANG_TARGET_ARM32 := --target=$(notdir $(CLANG_TRIPLE_ARM32:%-=%)) + export CONFIG_VDSO32 := y + vdso32 := -DCONFIG_VDSO32=1 + else ifeq ($(shell which $(CROSS_COMPILE_ARM32)$(cc-name) 2> /dev/null),) + $(error $(CROSS_COMPILE_ARM32)$(cc-name) not found, check CROSS_COMPILE_ARM32) + else + export CROSS_COMPILE_ARM32 + export CONFIG_VDSO32 := y + vdso32 := -DCONFIG_VDSO32=1 + endif +endif + +KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) $(vdso32) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_CFLAGS += $(call cc-option, -mpc-relative-literal-loads) -KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) +KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) $(vdso32) KBUILD_CFLAGS += $(call cc-option,-mabi=lp64) KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) @@ -157,6 +186,8 @@ archclean: prepare: vdso_prepare vdso_prepare: prepare0 $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso include/generated/vdso-offsets.h + $(if $(CONFIG_VDSO32),$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso32 \ + include/generated/vdso32-offsets.h) define archhelp echo '* Image.gz - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)' diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 6e969f3cde6c..5db2b239cd68 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -30,7 +30,9 @@ $(obj)/%.stub.o: $(obj)/%.o FORCE arm64-obj-$(CONFIG_COMPAT) += sys32.o signal32.o \ sys_compat.o entry32.o +ifneq ($(CONFIG_VDSO32),y) arm64-obj-$(CONFIG_COMPAT) += sigreturn32.o +endif arm64-obj-$(CONFIG_KUSER_HELPERS) += kuser32.o arm64-obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o arm64-obj-$(CONFIG_MODULES) += arm64ksyms.o module.o @@ -58,6 +60,7 @@ arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o obj-y += $(arm64-obj-y) vdso/ probes/ +obj-$(CONFIG_VDSO32) += vdso32/ obj-m += $(arm64-obj-m) head-y := head.o extra-y += $(head-y) vmlinux.lds -- 2.15.0.448.gf294e3d99a-goog
