Re: [PATCH v3] x86, kconfig: Default to ARCH=x86 to avoidoverriding CONFIG_64BIT
From: David Woodhouse
Date: Sat Jul 30 2011 - 16:59:50 EST
On Sat, 2011-07-30 at 11:59 -0700, H. Peter Anvin wrote:
> For klibc integration, we ran into this problem as well: the set of
> architectures for the kernel simply isn't the same set as the
> architectures for userspace. For the kernel, x86 is an architecture,
> for userspace the architectures are x86_64 or i386 and they are
> fundamentally different in many, many ways.
>
> The main problem with SUBARCH is that it is ill-defined in the general
> case if SUBARCH contains a user space or a kernel space architecture.
> In that sense I would much prefer it if was called, say, USERARCH and
> was always available. It could even be set by Kconfig
> (CONFIG_USERARCH?)
In the context of a kernel build that's meaningless though. One kernel
can support *many* types of userspace.
I've just been playing with ARCH=um. It looks like the current state,
even before my patch, is that 'make ARCH=um SUBARCH=x86' is broken.
I'll work on a patch to fix that, and then it will be fine when the
default for SUBARCH changes to be "x86".
(Another option is to make SUBARCH default to x86 *only* if ARCH!=um,
and still use the legacy SUBARCH values when ARCH=um. But I'm not overly
keen on that approach.)
Fixing um to work with ARCH=x86 *ought* to be as simple as doing
something like this:
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -12,6 +12,15 @@ OS := $(shell uname -s)
# features.
SHELL := /bin/bash
+# The i386/x86_64 merge hasn't really happened in um-land yet. Fake it.
+ifeq ($(SUBARCH),x86)
+ifeq ($(CONFIG_64BIT),y)
+SUBARCH := x86_64
+else
+SUBARCH := i386
+endif
+endif
+
filechk_gen_header = $<
core-y += $(ARCH_DIR)/kernel/ \
.. but that gives me weird behaviour where it just keeps running
silentoldconfig over and over again.
This patch *does* work, but I'll see if I can make it simpler...
diff --git a/arch/um/Kconfig.x86 b/arch/um/Kconfig.x86
index d31ecf3..576b732 100644
--- a/arch/um/Kconfig.x86
+++ b/arch/um/Kconfig.x86
@@ -19,8 +19,8 @@ config UML_X86
select GENERIC_FIND_FIRST_BIT
config 64BIT
- bool
- default SUBARCH = "x86_64"
+ bool "64-bit kernel" if SUBARCH = "x86"
+ default SUBARCH != "i386"
config X86_32
def_bool !64BIT
diff --git a/arch/um/Makefile b/arch/um/Makefile
index fab8121..562c6cb 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -12,6 +12,17 @@ OS := $(shell uname -s)
# features.
SHELL := /bin/bash
+# The i386/x86_64 merge hasn't really happened in um-land yet. Fake it.
+ifeq ($(SUBARCH),x86)
+ifeq ($(CONFIG_64BIT),y)
+UMSUBARCH := x86_64
+else
+UMSUBARCH := i386
+endif
+else
+UMSUBARCH := $(SUBARCH)
+endif
+
filechk_gen_header = $<
core-y += $(ARCH_DIR)/kernel/ \
@@ -24,11 +35,11 @@ include $(srctree)/$(ARCH_DIR)/Makefile-skas
SHARED_HEADERS := $(ARCH_DIR)/include/shared
ARCH_INCLUDE := -I$(srctree)/$(SHARED_HEADERS)
-ARCH_INCLUDE += -I$(srctree)/$(ARCH_DIR)/sys-$(SUBARCH)/shared
+ARCH_INCLUDE += -I$(srctree)/$(ARCH_DIR)/sys-$(UMSUBARCH)/shared
ifneq ($(KBUILD_SRC),)
ARCH_INCLUDE += -I$(SHARED_HEADERS)
endif
-KBUILD_CPPFLAGS += -I$(srctree)/$(ARCH_DIR)/sys-$(SUBARCH)
+KBUILD_CPPFLAGS += -I$(srctree)/$(ARCH_DIR)/sys-$(UMSUBARCH)
# -Dvmap=kernel_vmap prevents anything from referencing the libpcap.o symbol so
# named - it's a common symbol in libpcap, so we get a binary which crashes.
@@ -38,7 +49,7 @@ KBUILD_CPPFLAGS += -I$(srctree)/$(ARCH_DIR)/sys-$(SUBARCH)
#
# These apply to USER_CFLAGS to.
-KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(SUBARCH)\" \
+KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(UMSUBARCH)\" \
$(ARCH_INCLUDE) $(MODE_INCLUDE) -Dvmap=kernel_vmap \
-Din6addr_loopback=kernel_in6addr_loopback \
-Din6addr_any=kernel_in6addr_any
@@ -49,7 +60,7 @@ USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -D__KERNEL__,,\
$(patsubst -I%,,$(KBUILD_CFLAGS)))) $(ARCH_INCLUDE) $(MODE_INCLUDE) \
$(filter -I%,$(CFLAGS)) -D_FILE_OFFSET_BITS=64
-include $(srctree)/$(ARCH_DIR)/Makefile-$(SUBARCH)
+include $(srctree)/$(ARCH_DIR)/Makefile-$(UMSUBARCH)
#This will adjust *FLAGS accordingly to the platform.
include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS)
@@ -128,8 +139,8 @@ archclean:
# Generated files
-$(ARCH_DIR)/sys-$(SUBARCH)/user-offsets.s: FORCE
- $(Q)$(MAKE) $(build)=$(ARCH_DIR)/sys-$(SUBARCH) $@
+$(ARCH_DIR)/sys-$(UMSUBARCH)/user-offsets.s: FORCE
+ $(Q)$(MAKE) $(build)=$(ARCH_DIR)/sys-$(UMSUBARCH) $@
define filechk_gen-asm-offsets
(set -e; \
@@ -144,11 +155,11 @@ define filechk_gen-asm-offsets
echo ""; )
endef
-$(SHARED_HEADERS)/user_constants.h: $(ARCH_DIR)/sys-$(SUBARCH)/user-offsets.s
+$(SHARED_HEADERS)/user_constants.h: $(ARCH_DIR)/sys-$(UMSUBARCH)/user-offsets.s
$(call filechk,gen-asm-offsets)
$(SHARED_HEADERS)/kern_constants.h:
$(Q)mkdir -p $(dir $@)
$(Q)echo '#include "../../../../include/generated/asm-offsets.h"' >$@
-export SUBARCH USER_CFLAGS CFLAGS_NO_HARDENING OS HEADER_ARCH DEV_NULL_PATH
+export SUBARCH UMSUBARCH USER_CFLAGS CFLAGS_NO_HARDENING OS HEADER_ARCH DEV_NULL_PATH
diff --git a/arch/um/Makefile-i386 b/arch/um/Makefile-i386
index 302cbe5..b66063b 100644
--- a/arch/um/Makefile-i386
+++ b/arch/um/Makefile-i386
@@ -5,22 +5,22 @@ TOP_ADDR := $(CONFIG_TOP_ADDR)
START := 0x8048000
LDFLAGS += -m elf_i386
-ELF_ARCH := $(SUBARCH)
-ELF_FORMAT := elf32-$(SUBARCH)
+ELF_ARCH := $(UMSUBARCH)
+ELF_FORMAT := elf32-$(UMSUBARCH)
OBJCOPYFLAGS := -O binary -R .note -R .comment -S
HEADER_ARCH := x86
CHECKFLAGS += -D__i386__
-ifeq ("$(origin SUBARCH)", "command line")
-ifneq ("$(shell uname -m | sed -e s/i.86/i386/)", "$(SUBARCH)")
+#ifeq ("$(origin SUBARCH)", "command line")
+#ifneq ("$(shell uname -m | sed -e s/i.86/i386/)", "$(SUBARCH)")
KBUILD_CFLAGS += $(call cc-option,-m32)
KBUILD_AFLAGS += $(call cc-option,-m32)
LINK-y += $(call cc-option,-m32)
UML_OBJCOPYFLAGS += -F $(ELF_FORMAT)
export LDFLAGS HOSTCFLAGS HOSTLDFLAGS UML_OBJCOPYFLAGS
-endif
-endif
+#endif
+#endif
# First of all, tune CFLAGS for the specific CPU. This actually sets cflags-y.
include $(srctree)/arch/x86/Makefile_32.cpu
diff --git a/arch/um/os-Linux/Makefile b/arch/um/os-Linux/Makefile
index b33f4df..c1a2ca3 100644
--- a/arch/um/os-Linux/Makefile
+++ b/arch/um/os-Linux/Makefile
@@ -5,7 +5,7 @@
obj-y = aio.o execvp.o file.o helper.o irq.o main.o mem.o process.o \
registers.o sigio.o signal.o start_up.o time.o tty.o uaccess.o \
- umid.o tls.o user_syms.o util.o drivers/ sys-$(SUBARCH)/ skas/
+ umid.o tls.o user_syms.o util.o drivers/ sys-$(UMSUBARCH)/ skas/
obj-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
--
dwmw2
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