Re: [kees:for-next/hardening 2/2] drivers/misc/lkdtm/bugs.c:302:1: warning: 'noreturn' function does return

[Kees Cook <keescook@chromium.org>]

On Fri, Jan 26, 2024 at 07:58:46AM -0800, Doug Anderson wrote:
> Hi,
> 
> On Fri, Jan 26, 2024 at 6:56 AM kernel test robot <lkp@intel.com> wrote:
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/hardening
> > head:   edb6538da3df83806fffcfc1b873d0895c81b9e8
> > commit: edb6538da3df83806fffcfc1b873d0895c81b9e8 [2/2] lkdtm/bugs: Adjust lkdtm_HUNG_TASK() to avoid tail call optimization
> > config: mips-allyesconfig (https://download.01.org/0day-ci/archive/20240126/202401262204.wUFKRYZF-lkp@intel.com/config)
> > compiler: mips-linux-gcc (GCC) 13.2.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240126/202401262204.wUFKRYZF-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202401262204.wUFKRYZF-lkp@intel.com/
> >
> > All error/warnings (new ones prefixed by >>):
> >
> >    arch/mips/kernel/head.o: in function `__kernel_entry':
> > >> (.text+0x0): relocation truncated to fit: R_MIPS_26 against `kernel_entry'
> >    arch/mips/kernel/head.o: in function `smp_bootstrap':
> > >> (.ref.text+0xd8): relocation truncated to fit: R_MIPS_26 against `start_secondary'
> >    init/main.o: in function `set_reset_devices':
> >    main.c:(.init.text+0x10): relocation truncated to fit: R_MIPS_26 against `_mcount'
> >    main.c:(.init.text+0x18): relocation truncated to fit: R_MIPS_26 against `__sanitizer_cov_trace_pc'
> >    init/main.o: in function `debug_kernel':
> >    main.c:(.init.text+0x50): relocation truncated to fit: R_MIPS_26 against `_mcount'
> >    main.c:(.init.text+0x58): relocation truncated to fit: R_MIPS_26 against `__sanitizer_cov_trace_pc'
> >    init/main.o: in function `quiet_kernel':
> >    main.c:(.init.text+0x90): relocation truncated to fit: R_MIPS_26 against `_mcount'
> >    main.c:(.init.text+0x98): relocation truncated to fit: R_MIPS_26 against `__sanitizer_cov_trace_pc'
> >    init/main.o: in function `warn_bootconfig':
> >    main.c:(.init.text+0xd0): relocation truncated to fit: R_MIPS_26 against `_mcount'
> >    main.c:(.init.text+0xd8): relocation truncated to fit: R_MIPS_26 against `__sanitizer_cov_trace_pc'
> >    init/main.o: in function `init_setup':
> >    main.c:(.init.text+0x108): additional relocation overflows omitted from the output
> > --
> >    drivers/misc/lkdtm/bugs.c: In function 'lkdtm_HUNG_TASK':
> > >> drivers/misc/lkdtm/bugs.c:302:1: warning: 'noreturn' function does return
> >      302 | }
> >          | ^
> >
> >
> > vim +/noreturn +302 drivers/misc/lkdtm/bugs.c
> >
> > 00f496c416122e drivers/misc/lkdtm_bugs.c Kees Cook        2016-06-26  296
> > edb6538da3df83 drivers/misc/lkdtm/bugs.c Douglas Anderson 2024-01-22  297  static void __noreturn lkdtm_HUNG_TASK(void)
> > 00f496c416122e drivers/misc/lkdtm_bugs.c Kees Cook        2016-06-26  298  {
> > 00f496c416122e drivers/misc/lkdtm_bugs.c Kees Cook        2016-06-26  299       set_current_state(TASK_UNINTERRUPTIBLE);
> > 00f496c416122e drivers/misc/lkdtm_bugs.c Kees Cook        2016-06-26  300       schedule();
> > edb6538da3df83 drivers/misc/lkdtm/bugs.c Douglas Anderson 2024-01-22  301       BUG_ON(1);
> > 00f496c416122e drivers/misc/lkdtm_bugs.c Kees Cook        2016-06-26 @302  }
> 
> Ah, I see the problem. MIPS has its own BUG_ON that's an inline
> function instead of a macro and that means that the compiler can't
> figure out that my constant condition will always call BUG(). ...this
> should just be changed to BUG().
> 
> Patch fixing this at:
> 
> https://lore.kernel.org/r/20240126072852.1.Ib065e528a8620474a72f15baa2feead1f3d89865@changeid

Thanks for tracking this down! :)

-- 
Kees Cook