Hello,
Recently I meet a strange error when building a kernel: if I build the
kernel in the source tree, then it will work well; but if I build it
with O=../build, then the resulting kernel is unstable.
Looking into the problem, I find that these two kernel is quite
different, e.g.
ls -l */built-in.o in build/ dir:
-rw-r--r-- 1 loongson loongson 155239 2007-03-30 10:21 block/built-in.o
-rw-r--r-- 1 loongson loongson 18923 2007-03-30 10:20 crypto/built-in.o
-rw-r--r-- 1 loongson loongson 1498144 2007-03-30 10:30 drivers/built-in.o
-rw-r--r-- 1 loongson loongson 1075678 2007-03-30 10:20 fs/built-in.o
-rw-r--r-- 1 loongson loongson 48747 2007-03-30 22:24 init/built-in.o
-rw-r--r-- 1 loongson loongson 38110 2007-03-30 10:20 ipc/built-in.o
-rw-r--r-- 1 loongson loongson 468469 2007-03-30 10:18 kernel/built-in.o
-rw-r--r-- 1 loongson loongson 18898 2007-03-30 10:41 lib/built-in.o
-rw-r--r-- 1 loongson loongson 313511 2007-03-30 10:12 mm/built-in.o
-rw-r--r-- 1 loongson loongson 974689 2007-03-30 10:40 net/built-in.o
-rw-r--r-- 1 loongson loongson 6774 2007-03-30 10:20 security/built-in.o
-rw-r--r-- 1 loongson loongson 8 2007-03-30 22:43 sound/built-in.o
-rw-r--r-- 1 loongson loongson 913 2007-03-30 10:07 usr/built-in.o
ls -l */built-in.o in src tree:
-rw-r--r-- 1 loongson loongson 155484 2007-03-29 23:03 block/built-in.o
-rw-r--r-- 1 loongson loongson 21702 2007-03-29 23:01 crypto/built-in.o
-rw-r--r-- 1 loongson loongson 1771957 2007-03-29 23:26 drivers/built-in.o
-rw-r--r-- 1 loongson loongson 1087193 2007-03-29 23:00 fs/built-in.o
-rw-r--r-- 1 loongson loongson 48747 2007-03-30 22:21 init/built-in.o
-rw-r--r-- 1 loongson loongson 54546 2007-03-29 23:01 ipc/built-in.o
-rw-r--r-- 1 loongson loongson 470917 2007-03-30 10:16 kernel/built-in.o
-rw-r--r-- 1 loongson loongson 23356 2007-03-29 23:51 lib/built-in.o
-rw-r--r-- 1 loongson loongson 314543 2007-03-29 22:30 mm/built-in.o
-rw-r--r-- 1 loongson loongson 935894 2007-03-29 23:50 net/built-in.o
-rw-r--r-- 1 loongson loongson 6774 2007-03-29 23:01 security/built-in.o
-rw-r--r-- 1 loongson loongson 12154 2007-03-30 22:21 sound/built-in.o
-rw-r--r-- 1 loongson loongson 894 2007-03-29 22:20 usr/built-in.o
loongson@debian:~/old$ ls -l vmlinux ../build-old/vmlinux
-rwxr-xr-x 1 loongson loongson 3856719 2007-03-30 22:24 ../build-old/vmlinux
-rwxr-xr-x 1 loongson loongson 4079730 2007-03-30 22:21 vmlinux
the size different is around 200K!
Take the "sound" subdir for example, I use Make V=1 to check the output
and find that
while in the src tree, obj-y is correctly set to soundcore.o, so
built-in.o will be linked
using: (CONFIG_SOUND=y)
make -f scripts/Makefile.build obj=sound
ld -m elf32ltsmip -r -o sound/built-in.o sound/soundcore.o
while with O= option:
make -f /home/loongson/old/scripts/Makefile.build obj=sound
rm -f sound/built-in.o; ar rcs sound/built-in.o
check scripts/Makefile.build we can find that it indicates that obj-y is
null:
around line 260:
ifdef builtin-target
quiet_cmd_link_o_target = LD $@
# If the list of objects to link is empty, just create an empty built-in.o
cmd_link_o_target = $(if $(strip $(obj-y)),\
$(LD) $(ld_flags) -r -o $@ $(filter $(obj-y), $^),\
rm -f $@; $(AR) rcs $@)
$(builtin-target): $(obj-y) FORCE
$(call if_changed,link_o_target)
Anybody can help explain this?
Thank you.
yours
Fuxin Zhang
