[WARNING -mm] 2.6.18-rc2-mm1 build kills /dev/null!?

[WARNING -mm] 2.6.18-rc2-mm1 build kills /dev/null!?

[Andreas Mohr]

Hello all,

for some reason a 2.6.18-rc2-mm1 build seems to kill my /dev/null device!

A simple
# make bzImage modules modules_install
managed to reduce my

crw-rw-rw-    1 root     root       1,   3 27. Jul 12:04 null

into the charred remains equivalent of

-rw-r--r--    1 root     root            0 27. Jul 12:02 null

, *twice* (I tried it the first time and had that issue,
then rebuilt the device and rebooted, same problem once build started).

Any idea why this might happen?

This did not happen with a 2.6.18-rc1-mm2 build.

A simple

rm /dev/null
mknod /dev/null c 1 3
chmod 666 /dev/null

corrects the problem, BTW.

Thanks,

Andreas Mohr

Re: [WARNING -mm] 2.6.18-rc2-mm1 build kills /dev/null!?

[Andreas Mohr]

Hi,

On Thu, Jul 27, 2006 at 12:11:28PM +0200, Andreas Mohr wrote:
> Hello all,
> 
> for some reason a 2.6.18-rc2-mm1 build seems to kill my /dev/null device!

Replying to myself, this could easily be due to:

--- linux-2.6.18-rc2/scripts/Kbuild.include     2006-07-15 21:41:08.000000000 -
0700
+++ devel/scripts/Kbuild.include        2006-07-27 01:15:54.000000000 -0700
@@ -8,9 +8,13 @@ empty   :=
 space   := $(empty) $(empty)

 ###
+# Name of target with a '.' as filename prefix. foo/bar.o => foo/.bar.o
+dot-target = $(dir $@).$(notdir $@)
+
+###
 # The temporary file to save gcc -MD generated dependencies must not
 # contain a comma
-depfile = $(subst $(comma),_,$(@D)/.$(@F).d)
+depfile = $(subst $(comma),_,$(dot-target).d)

 ###
 # filename of target with directory and extension stripped
@@ -59,6 +63,12 @@ as-option = $(shell if $(CC) $(CFLAGS) $
             -xassembler /dev/null > /dev/null 2>&1; then echo "$(1)"; \
             else echo "$(2)"; fi ;)

+# as-instr
+# Usage: cflags-y += $(call as-instr, instr, option1, option2)
+
+as-instr = $(shell if echo -e "$(1)" | $(AS) -Z -o /dev/null \
+                  2>&1 >/dev/null ; then echo "$(2)"; else echo "$(3)"; fi;)
+
 # cc-option
 # Usage: cflags-y += $(call cc-option, -march=winchip-c6, -march=i586)

@@ -77,14 +87,19 @@ cc-option-align = $(subst -functions=0,,

 # cc-version
 # Usage gcc-ver := $(call cc-version, $(CC))
-cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh \
-              $(if $(1), $(1), $(CC)))
+cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh $(CC))

 # cc-ifversion
 # Usage:  EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
 cc-ifversion = $(shell if [ $(call cc-version, $(CC)) $(1) $(2) ]; then \
                        echo $(3); fi;)

+# ld-option
+# Usage: ldflags += $(call ld-option, -Wl$(comma)--hash-style=both)
+ld-option = $(shell if $(CC) $(1) \
+                            -nostdlib -o /dev/null -xc /dev/null \
+             > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi)
+


Possibly an older binutils doesn't have a "if *output* file /dev/null,
then kill output instead of overwriting file" check builtin as IIRC newer
utils often have?

# which ld
/usr/bin/ld

# rpm -qf /usr/bin/ld
binutils-2.15.92.0.2-5

Andreas Mohr

Re: [WARNING -mm] 2.6.18-rc2-mm1 build kills /dev/null!?

[Andreas Mohr]

On Thu, Jul 27, 2006 at 12:17:09PM +0200, Andreas Mohr wrote:
> Hi,
> 
> On Thu, Jul 27, 2006 at 12:11:28PM +0200, Andreas Mohr wrote:
> > Hello all,
> > 
> > for some reason a 2.6.18-rc2-mm1 build seems to kill my /dev/null device!
> 
> Replying to myself, this could easily be due to:

Yup, seems it is, see newly posted:

"Re: [PATCH] vDSO hash-style fix"
http://lkml.org/lkml/2006/7/27/83

| > +# ld-option
| > +# Usage: ldflags += $(call ld-option, -Wl$(comma)--hash-style=both)
| > +ld-option = $(shell if $(CC) $(1) \
| > +			     -nostdlib -o /dev/null -xc /dev/null \
| > +             > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi)
| 
| This is not good. When I introduced something similar for lxdialog I
| received lots of reports about /dev/null becoming a regular file.
| ld does something strange with the output file when it fails.
| 
| When re-done ld-option shall be accompanied by documentation in
| Documentation/makefiles.txt like cc-option.

Could we have a -mm hot-fix here?

Andreas Mohr

Re: [WARNING -mm] 2.6.18-rc2-mm1 build kills /dev/null!?

[Michael Tokarev]

Andreas Mohr wrote:
> Hello all,
> 
> for some reason a 2.6.18-rc2-mm1 build seems to kill my /dev/null device!
> 
> A simple
> # make bzImage modules modules_install
> managed to reduce my
> 
> crw-rw-rw-    1 root     root       1,   3 27. Jul 12:04 null
> 
> into the charred remains equivalent of
> 
> -rw-r--r--    1 root     root            0 27. Jul 12:02 null

Don't build as root.

While something's broke in kernel build scripts and probably
should be fixed, it's not a reason for anyone to get their
whole filesystem rm -rf'ed.

/mjt

Re: [WARNING -mm] 2.6.18-rc2-mm1 build kills /dev/null!?

[gmu 2k6]

On 7/27/06, Michael Tokarev <mjt@tls.msk.ru> wrote:
> Andreas Mohr wrote:
> > Hello all,
> >
> > for some reason a 2.6.18-rc2-mm1 build seems to kill my /dev/null device!
> >
> > A simple
> > # make bzImage modules modules_install
> > managed to reduce my
> >
> > crw-rw-rw-    1 root     root       1,   3 27. Jul 12:04 null
> >
> > into the charred remains equivalent of
> >
> > -rw-r--r--    1 root     root            0 27. Jul 12:02 null
>
> Don't build as root.
>
> While something's broke in kernel build scripts and probably
> should be fixed, it's not a reason for anyone to get their
> whole filesystem rm -rf'ed.

and it does not matter if you're using udev:
$ ls -l /dev/null
crw-rw-rw- 1 root root 1, 3 2006-07-27 11:42 /dev/null

Re: [WARNING -mm] 2.6.18-rc2-mm1 build kills /dev/null!?

[gmu 2k6]

On 7/27/06, gmu 2k6 <gmu2006@gmail.com> wrote:
> On 7/27/06, Michael Tokarev <mjt@tls.msk.ru> wrote:
> > Andreas Mohr wrote:
> > > Hello all,
> > >
> > > for some reason a 2.6.18-rc2-mm1 build seems to kill my /dev/null device!
> > >
> > > A simple
> > > # make bzImage modules modules_install
> > > managed to reduce my
> > >
> > > crw-rw-rw-    1 root     root       1,   3 27. Jul 12:04 null
> > >
> > > into the charred remains equivalent of
> > >
> > > -rw-r--r--    1 root     root            0 27. Jul 12:02 null
> >
> > Don't build as root.
> >
> > While something's broke in kernel build scripts and probably
> > should be fixed, it's not a reason for anyone to get their
> > whole filesystem rm -rf'ed.
>
> and it does not matter if you're using udev:
> $ ls -l /dev/null
> crw-rw-rw- 1 root root 1, 3 2006-07-27 11:42 /dev/null

actually this is so obvious I should not have posted that reply. sorry guys.