Add vDSO compat support to the arm64 building system.

Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Vincenzo Frascino <[email protected]>
---
 arch/arm64/Kconfig         |  1 +
 arch/arm64/Makefile        | 23 +++++++++++++++++++++--
 arch/arm64/kernel/Makefile |  6 +++++-
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 952c9f8cf3b8..3e1d4f8347f4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -108,6 +108,7 @@ config ARM64
        select GENERIC_STRNLEN_USER
        select GENERIC_TIME_VSYSCALL
        select GENERIC_GETTIMEOFDAY
+       select GENERIC_COMPAT_VDSO if !CPU_BIG_ENDIAN
        select HANDLE_DOMAIN_IRQ
        select HARDIRQS_SW_RESEND
        select HAVE_PCI
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index b025304bde46..4db50d4b2476 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -49,9 +49,25 @@ $(warning Detected assembler with broken .inst; disassembly 
will be unreliable)
   endif
 endif
 
-KBUILD_CFLAGS  += -mgeneral-regs-only $(lseinstr) $(brokengasinst)
+ifeq ($(CONFIG_GENERIC_COMPAT_VDSO), y)
+  CROSS_COMPILE_COMPAT ?= $(CONFIG_CROSS_COMPILE_COMPAT_VDSO:"%"=%)
+
+  ifeq ($(CONFIG_CC_IS_CLANG), y)
+    $(warning CROSS_COMPILE_COMPAT is clang, the compat vDSO will not be built)
+  else ifeq ($(CROSS_COMPILE_COMPAT),)
+    $(warning CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will 
not be built)
+  else ifeq ($(shell which $(CROSS_COMPILE_COMPAT)gcc 2> /dev/null),)
+    $(error $(CROSS_COMPILE_COMPAT)gcc not found, check CROSS_COMPILE_COMPAT)
+  else
+    export CROSS_COMPILE_COMPAT
+    export CONFIG_COMPAT_VDSO := y
+    compat_vdso := -DCONFIG_COMPAT_VDSO=1
+  endif
+endif
+
+KBUILD_CFLAGS  += -mgeneral-regs-only $(lseinstr) $(brokengasinst) 
$(compat_vdso)
 KBUILD_CFLAGS  += -fno-asynchronous-unwind-tables
-KBUILD_AFLAGS  += $(lseinstr) $(brokengasinst)
+KBUILD_AFLAGS  += $(lseinstr) $(brokengasinst) $(compat_vdso)
 
 KBUILD_CFLAGS  += $(call cc-option,-mabi=lp64)
 KBUILD_AFLAGS  += $(call cc-option,-mabi=lp64)
@@ -163,6 +179,9 @@ ifeq ($(KBUILD_EXTMOD),)
 prepare: vdso_prepare
 vdso_prepare: prepare0
        $(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso 
include/generated/vdso-offsets.h
+       $(if $(CONFIG_COMPAT_VDSO),$(Q)$(MAKE) \
+               $(build)=arch/arm64/kernel/vdso32  \
+               include/generated/vdso32-offsets.h)
 endif
 
 define archhelp
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 9e7dcb2c31c7..478491f07b4f 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -28,7 +28,10 @@ $(obj)/%.stub.o: $(obj)/%.o FORCE
        $(call if_changed,objcopy)
 
 obj-$(CONFIG_COMPAT)                   += sys32.o signal32.o                   
\
-                                          sigreturn32.o sys_compat.o
+                                          sys_compat.o
+ifneq ($(CONFIG_COMPAT_VDSO), y)
+obj-$(CONFIG_COMPAT)                   += sigreturn32.o
+endif
 obj-$(CONFIG_KUSER_HELPERS)            += kuser32.o
 obj-$(CONFIG_FUNCTION_TRACER)          += ftrace.o entry-ftrace.o
 obj-$(CONFIG_MODULES)                  += module.o
@@ -62,6 +65,7 @@ obj-$(CONFIG_ARM64_SSBD)              += ssbd.o
 obj-$(CONFIG_ARM64_PTR_AUTH)           += pointer_auth.o
 
 obj-y                                  += vdso/ probes/
+obj-$(CONFIG_COMPAT_VDSO)              += vdso32/
 head-y                                 := head.o
 extra-y                                        += $(head-y) vmlinux.lds
 
-- 
2.21.0

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