mips gcc plugin issues

mips gcc plugin issues

[Jeff Johnson]

I'm trying to do an allmodconfig build for ARCH=mips using:
https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/13.2.0/x86_64-gcc-13.2.0-nolibc-mips-linux.tar.gz

This build dies quickly with:
  CC      scripts/mod/empty.o
cc1: error: cannot load plugin ./scripts/gcc-plugins/randomize_layout_plugin.so: ./scripts/gcc-plugins/randomize_layout_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
cc1: error: cannot load plugin ./scripts/gcc-plugins/latent_entropy_plugin.so: ./scripts/gcc-plugins/latent_entropy_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
  CC      scripts/mod/devicetable-offsets.s
make[2]: *** [scripts/Makefile.build:244: scripts/mod/empty.o] Error 1
make[2]: *** Waiting for unfinished jobs....
cc1: error: cannot load plugin ./scripts/gcc-plugins/randomize_layout_plugin.so: ./scripts/gcc-plugins/randomize_layout_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
cc1: error: cannot load plugin ./scripts/gcc-plugins/latent_entropy_plugin.so: ./scripts/gcc-plugins/latent_entropy_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
  HDRINST usr/include/linux/usb/tmc.h
make[2]: *** [scripts/Makefile.build:117: scripts/mod/devicetable-offsets.s] Error 1

I see the following in my .config:
CONFIG_HAVE_GCC_PLUGINS=y
CONFIG_GCC_PLUGINS=y
CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y
CONFIG_GCC_PLUGIN_RANDSTRUCT=y

So I'll turn those off, but just want to flag that this issue exists.
Seems either the plugins should work or the allmodconfig should turn them off.

/jeff

Re: mips gcc plugin issues

[Kees Cook]

On Tue, Jun 18, 2024 at 04:41:01PM -0700, Jeff Johnson wrote:
> I'm trying to do an allmodconfig build for ARCH=mips using:
> https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/13.2.0/x86_64-gcc-13.2.0-nolibc-mips-linux.tar.gz
> 
> This build dies quickly with:
>   CC      scripts/mod/empty.o
> cc1: error: cannot load plugin ./scripts/gcc-plugins/randomize_layout_plugin.so: ./scripts/gcc-plugins/randomize_layout_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
> cc1: error: cannot load plugin ./scripts/gcc-plugins/latent_entropy_plugin.so: ./scripts/gcc-plugins/latent_entropy_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
>   CC      scripts/mod/devicetable-offsets.s
> make[2]: *** [scripts/Makefile.build:244: scripts/mod/empty.o] Error 1
> make[2]: *** Waiting for unfinished jobs....
> cc1: error: cannot load plugin ./scripts/gcc-plugins/randomize_layout_plugin.so: ./scripts/gcc-plugins/randomize_layout_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
> cc1: error: cannot load plugin ./scripts/gcc-plugins/latent_entropy_plugin.so: ./scripts/gcc-plugins/latent_entropy_plugin.so: undefined symbol: _ZNK6frange6acceptERK14vrange_visitor
>   HDRINST usr/include/linux/usb/tmc.h
> make[2]: *** [scripts/Makefile.build:117: scripts/mod/devicetable-offsets.s] Error 1
> 
> I see the following in my .config:
> CONFIG_HAVE_GCC_PLUGINS=y
> CONFIG_GCC_PLUGINS=y
> CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y
> CONFIG_GCC_PLUGIN_RANDSTRUCT=y
> 
> So I'll turn those off, but just want to flag that this issue exists.
> Seems either the plugins should work or the allmodconfig should turn them off.

Well, the plugins work with all the other compiler versions all the
various CI systems use. :) For example, I don't see this with distro
cross compilers:

$ mipsel-linux-gnu-gcc --version
mipsel-linux-gnu-gcc (Ubuntu 12.3.0-1ubuntu1) 12.3.0

I suspect this is a problem with the kernel.org crosstool builds? I'm
CCing Arnd, who might know more about this.

-Kees

-- 
Kees Cook

Re: mips gcc plugin issues

[Arnd Bergmann]

On Wed, Jun 19, 2024, at 22:50, Kees Cook wrote:
> On Tue, Jun 18, 2024 at 04:41:01PM -0700, Jeff Johnson wrote:
>> I see the following in my .config:
>> CONFIG_HAVE_GCC_PLUGINS=y
>> CONFIG_GCC_PLUGINS=y
>> CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y
>> CONFIG_GCC_PLUGIN_RANDSTRUCT=y
>> 
>> So I'll turn those off, but just want to flag that this issue exists.
>> Seems either the plugins should work or the allmodconfig should turn them off.
>
> Well, the plugins work with all the other compiler versions all the
> various CI systems use. :) For example, I don't see this with distro
> cross compilers:
>
> $ mipsel-linux-gnu-gcc --version
> mipsel-linux-gnu-gcc (Ubuntu 12.3.0-1ubuntu1) 12.3.0
>
> I suspect this is a problem with the kernel.org crosstool builds? I'm
> CCing Arnd, who might know more about this.

Yes, this is a known problem, and I don't think there is a good
solution for it, compiler plugins on cross-compilers are inherently
fragile.

The problem here is that a gcc plugin links against the
compiler, not against code produced by it. I'm linking the
crosstool compilers statically against libraries as much as
possible in order to make them more portable between distros,
but the downside of that is that plugins will only work in
the environment that I was using to build these toolchains.

My build environment is an older Debian (in order to be
portable to old glibc versions), but with the system compiler
updated to gcc-13 (since x86 libgcc cannot be cross-compiled
with an older compiler).

The long-term solution of course is to replace all the
gcc plugins with some other way of getting the same
features, but that will still take some time.

     Arnd

Re: mips gcc plugin issues

[Kees Cook]

On Wed, Jun 19, 2024 at 11:12:25PM +0200, Arnd Bergmann wrote:
> On Wed, Jun 19, 2024, at 22:50, Kees Cook wrote:
> > On Tue, Jun 18, 2024 at 04:41:01PM -0700, Jeff Johnson wrote:
> >> I see the following in my .config:
> >> CONFIG_HAVE_GCC_PLUGINS=y
> >> CONFIG_GCC_PLUGINS=y
> >> CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y
> >> CONFIG_GCC_PLUGIN_RANDSTRUCT=y
> >> 
> >> So I'll turn those off, but just want to flag that this issue exists.
> >> Seems either the plugins should work or the allmodconfig should turn them off.
> >
> > Well, the plugins work with all the other compiler versions all the
> > various CI systems use. :) For example, I don't see this with distro
> > cross compilers:
> >
> > $ mipsel-linux-gnu-gcc --version
> > mipsel-linux-gnu-gcc (Ubuntu 12.3.0-1ubuntu1) 12.3.0
> >
> > I suspect this is a problem with the kernel.org crosstool builds? I'm
> > CCing Arnd, who might know more about this.
> 
> Yes, this is a known problem, and I don't think there is a good
> solution for it, compiler plugins on cross-compilers are inherently
> fragile.
> 
> The problem here is that a gcc plugin links against the
> compiler, not against code produced by it. I'm linking the
> crosstool compilers statically against libraries as much as
> possible in order to make them more portable between distros,
> but the downside of that is that plugins will only work in
> the environment that I was using to build these toolchains.
> 
> My build environment is an older Debian (in order to be
> portable to old glibc versions), but with the system compiler
> updated to gcc-13 (since x86 libgcc cannot be cross-compiled
> with an older compiler).

Can the crosstools remove the plugin support? That seems like the best
solution. Kconfig test for plugin availability with:

	depends on $(success,test -e $(shell,$(CC) -print-file-name=plugin)/include/plugin-version.h)

> The long-term solution of course is to replace all the
> gcc plugins with some other way of getting the same
> features, but that will still take some time.

Agreed. There's not much motion on the GCC side of this, though.

-- 
Kees Cook

Re: mips gcc plugin issues

[Arnd Bergmann]

On Wed, Jun 19, 2024, at 23:17, Kees Cook wrote:
> On Wed, Jun 19, 2024 at 11:12:25PM +0200, Arnd Bergmann wrote:
>> On Wed, Jun 19, 2024, at 22:50, Kees Cook wrote:

>> The problem here is that a gcc plugin links against the
>> compiler, not against code produced by it. I'm linking the
>> crosstool compilers statically against libraries as much as
>> possible in order to make them more portable between distros,
>> but the downside of that is that plugins will only work in
>> the environment that I was using to build these toolchains.
>> 
>> My build environment is an older Debian (in order to be
>> portable to old glibc versions), but with the system compiler
>> updated to gcc-13 (since x86 libgcc cannot be cross-compiled
>> with an older compiler).
>
> Can the crosstools remove the plugin support? That seems like the best
> solution. Kconfig test for plugin availability with:
>
> 	depends on $(success,test -e $(shell,$(CC) 
> -print-file-name=plugin)/include/plugin-version.h)

Good idea, yes. I still have to upload gcc-14.1 and gcc-13.3 binaries
anyway, so I'll try turning off plugin support when I build it.

      Arnd