[PATCH 1/3] 2.6.8-rc4-mm1 - Fix UML build

Jeff Dike
2004-08-12T03:14:33Z

The patch below makes UML build in the face of the ldchk addition to 2.6.8.
The basic problem for UML is that it has always had a two-stage link to produce
the final executable -
vmlinux contains all the kernel bits, but no libc or gcc libs
linux is vmlinux plus another .o, massaged by gcc, and linked against
libc

This means that, for UML, vmlinux will have unresolved symbols, and will fail
the ldchk test.

I fixed this in a reasonably nasty way by
adding a $(post-y) to the end of the list of objects
defining it to be
some link flags, an object, and a library from the old linux
link command
a set of libraries pulled from the output of 'gcc -v'
adding a -L flag to LDFLAGS_vmlinux which points at the location of
the -lgcc, etc libraries - this is determined by using 'gcc -v'
to figure out where its spec file is located and assuming that
its libraries will be located in the same place
adding arch/um/main.o to $(extra-y) in arch/um/kernel/Makefile because
I couldn't figure out how to get it to build from
arch/um/Makefile

This is all inside UML, except for the $(post-y) in the top-level Makefile.

With this, vmlinux contains all the bits needed for UML, and passes the ldchk
test. However, it won't run, and a gcc run is needed in order to produce a
real executable. gcc needs to polish the bits or something.

This getting entirely too familiar with gcc, and I'd appreciate clues about
how to back out of this. Ideally, I'd like to use the gcc driver as the
vmlinux linker, but that would require at least rewriting the command, so
I'm not sure how practical that is.

Anyway, you have been warned. Here it is. Andrew, please apply.

Jeff

Index: 2.6.8-rc4-mm1/Makefile
===================================================================
--- 2.6.8-rc4-mm1.orig/Makefile 2004-08-11 22:44:43.000000000 -0400
+++ 2.6.8-rc4-mm1/Makefile 2004-08-11 22:44:49.000000000 -0400
@@ -519,6 +519,7 @@
$(drivers-y) \
$(net-y) \
--end-group \
+ $(post-y) \
$(filter .tmp_kallsyms%,$^) \
-o $@
endef
Index: 2.6.8-rc4-mm1/arch/um/Makefile
===================================================================
--- 2.6.8-rc4-mm1.orig/arch/um/Makefile 2004-08-11 22:44:43.000000000 -0400
+++ 2.6.8-rc4-mm1/arch/um/Makefile 2004-08-11 22:44:49.000000000 -0400
@@ -21,6 +21,10 @@
$(ARCH_DIR)/drivers/ \
$(ARCH_DIR)/sys-$(SUBARCH)/

+post-y = --wrap malloc --wrap free --wrap calloc \
+ $(ARCH_DIR)/main.o -lutil \
+ --start-group -lgcc -lgcc_eh -lc --end-group
+
# Have to precede the include because the included Makefiles reference them.
SYMLINK_HEADERS = archparam.h system.h sigcontext.h processor.h ptrace.h \
arch-signal.h module.h
@@ -84,7 +88,10 @@

prepare: $(ARCH_SYMLINKS) $(SYS_HEADERS) $(GEN_HEADERS)

-LDFLAGS_vmlinux = -r
+# This stupidity extracts the directory in which gcc lives so that it can
+# be fed to ld when it's linking .tmp_vmlinux during the ldchk stage.
+LD_DIR = $(shell dirname `gcc -v 2>&1 | head -1 | awk '{print $$NF}'`)
+LDFLAGS_vmlinux = -L/usr/lib -L$(LD_DIR) -r

vmlinux: $(ARCH_DIR)/main.o

@@ -126,8 +133,7 @@
# $(call if_changed_dep,as_s_S)

linux: vmlinux $(LD_SCRIPT-y)
- $(CC) -Wl,-T,$(LD_SCRIPT-y) $(LINK-y) $(LINK_WRAPS) \
- -o linux $(ARCH_DIR)/main.o vmlinux -L/usr/lib -lutil
+ $(CC) -Wl,-T,$(LD_SCRIPT-y) $(LINK-y) -o linux vmlinux

USER_CFLAGS := $(patsubst -I%,,$(CFLAGS))
USER_CFLAGS := $(patsubst -Derrno=kernel_errno,,$(USER_CFLAGS))
Index: 2.6.8-rc4-mm1/arch/um/kernel/Makefile
===================================================================
--- 2.6.8-rc4-mm1.orig/arch/um/kernel/Makefile 2004-08-11 22:44:43.000000000 -0400
+++ 2.6.8-rc4-mm1/arch/um/kernel/Makefile 2004-08-11 22:44:49.000000000 -0400
@@ -3,7 +3,7 @@
# Licensed under the GPL
#

-extra-y := vmlinux.lds.s
+extra-y := vmlinux.lds.s ../main.o

obj-y = checksum.o config.o exec_kern.o exitcode.o frame_kern.o frame.o \
helper.o init_task.o irq.o irq_user.o ksyms.o mem.o mem_user.o \
@@ -24,7 +24,7 @@
user-objs-$(CONFIG_TTY_LOG) += tty_log.o

USER_OBJS := $(filter %_user.o,$(obj-y)) $(user-objs-y) config.o helper.o \
- process.o tempfile.o time.o tty_log.o umid.o user_util.o
+ process.o tempfile.o time.o tty_log.o umid.o user_util.o ../main.o
USER_OBJS := $(foreach file,$(USER_OBJS),$(obj)/$(file))

CFLAGS_frame.o := $(patsubst -fomit-frame-pointer,,$(USER_CFLAGS))
Index: 2.6.8-rc4-mm1/arch/um/kernel/vmlinux.lds.S
===================================================================
--- 2.6.8-rc4-mm1.orig/arch/um/kernel/vmlinux.lds.S 2004-08-11 22:44:43.000000000 -0400
+++ 2.6.8-rc4-mm1/arch/um/kernel/vmlinux.lds.S 2004-08-11 22:44:49.000000000 -0400
@@ -42,11 +42,10 @@

#include "asm/common.lds.S"

- init.data : { *(init.data) }
+ .init.data : { *(init.data) }
+ .data.init_task : { *(.data.init_task) }
.data :
{
- . = ALIGN(KERNEL_STACK_SIZE); /* init_task */
- *(.data.init_task)
*(.data)
*(.gnu.linkonce.d*)
CONSTRUCTORS
Index: 2.6.8-rc4-mm1/arch/um/sys-i386/Makefile
===================================================================
--- 2.6.8-rc4-mm1.orig/arch/um/sys-i386/Makefile 2004-08-11 22:44:43.000000000 -0400
+++ 2.6.8-rc4-mm1/arch/um/sys-i386/Makefile 2004-08-11 22:44:49.000000000 -0400
@@ -1,5 +1,5 @@
-obj-y = bugs.o checksum.o fault.o ksyms.o ldt.o ptrace.o ptrace_user.o \
- semaphore.o sigcontext.o syscalls.o sysrq.o time.o
+obj-y = bitops.o bugs.o checksum.o fault.o ksyms.o ldt.o ptrace.o \
+ ptrace_user.o semaphore.o sigcontext.o syscalls.o sysrq.o time.o

obj-$(CONFIG_HIGHMEM) += highmem.o
obj-$(CONFIG_MODULES) += module.o
@@ -7,11 +7,12 @@
USER_OBJS := bugs.o ptrace_user.o sigcontext.o fault.o
USER_OBJS := $(foreach file,$(USER_OBJS),$(obj)/$(file))

-SYMLINKS = semaphore.c highmem.c module.c
+SYMLINKS = bitops.c semaphore.c highmem.c module.c
SYMLINKS := $(foreach f,$(SYMLINKS),$(src)/$f)

clean-files := $(SYMLINKS)

+bitops.c-dir = lib
semaphore.c-dir = kernel
highmem.c-dir = mm
module.c-dir = kernel
Index: 2.6.8-rc4-mm1/arch/um/uml.lds.S
===================================================================
--- 2.6.8-rc4-mm1.orig/arch/um/uml.lds.S 2004-08-11 22:44:43.000000000 -0400
+++ 2.6.8-rc4-mm1/arch/um/uml.lds.S 2004-08-11 22:44:49.000000000 -0400
@@ -11,15 +11,9 @@

__binary_start = .;
#ifdef MODE_TT
- .thread_private : {
- __start_thread_private = .;
- errno = .;
- . += 4;
- arch/um/kernel/tt/unmap_fin.o (.data)
- __end_thread_private = .;
- }
+ .thread_private : { *(.thread_private) }
. = ALIGN(4096);
- .remap : { arch/um/kernel/tt/unmap_fin.o (.text) }
+ .remap : { *(.remap) }
#endif

. = ALIGN(4096); /* Init code and data */