linux-kernel - Re: [PATCH] Enable '-Werror' by default for all kernel builds

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Date:   Tue, 7 Sep 2021 13:32:36 +0800
From:   Huang Rui <ray.huang@....com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
CC:     Guenter Roeck <linux@...ck-us.net>,
        "David S. Miller" <davem@...emloft.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-sparc <sparclinux@...r.kernel.org>
Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds

On Tue, Sep 07, 2021 at 07:06:04AM +0800, Linus Torvalds wrote:
> [ Adding some subsystem maintainers ]
> 
> On Mon, Sep 6, 2021 at 10:06 AM Guenter Roeck <linux@...ck-us.net> wrote:
> >
> > > But hopefully most cases are just "people haven't cared enough" and
> > > easily fixed.
> >
> > We'll see. For my testbed I disabled the new configuration flag
> > for the time being because its primary focus is boot tests, and
> > there won't be any boot tests if images fail to build.
> 
> Sure, reasonable.
> 
> I've checked a few of the build errors by doing the appropriate cross
> compiles, and it doesn't seem bad - but it does seem like we have a
> number of really pointless long-standing warnings that should have
> been fixed long ago.
> 
> For example, looking at sparc64, there are several build errors due to
> those warnings now being fatal:
> 
>  - drivers/gpu/drm/ttm/ttm_pool.c:386
> 
>    This is a type mismatch error. It looks like __fls() on sparc64
> returns 'int'. And the ttm_pool.c code assumes it returns 'unsigned
> long'.
> 
>    Oddly enough, the very line after that line does "min_t(unsigned
> int" to get the types in line.
> 
>    So  the immediate reason is "sparc64 is different". But the deeper
> reason seems to be that ttm_pool.c has odd type assumptions. But that
> warning should have been fixed long ago, either way.
> 
>    Christian/Huang? I get the feeling that both lines in that file
> should use the min_t(). Hmm?


Shall we align the return type like __fls() on all the arches?

But it looks OK for me to change min to min_t() here as well, I can file a
patch to the update:

-       for (order = min(MAX_ORDER - 1UL, __fls(num_pages)); num_pages;
+       for (order = min_t(unsigned int, MAX_ORDER - 1UL, __fls(num_pages)); num_pages;

Christian, what's your opinion?

Thanks,
Ray

> 
>  - drivers/input/joystick/analog.c:160
> 
>    #warning Precise timer not defined for this architecture.
> 
>    Unfortunate. I suspect that warning just has to be removed. It has
> never caused anything to be fixed, it's old to the point of predating
> the git history. Dmitry?
> 
>  - at least a couple of stringop-overread errors. Attached is a
> possible for for one of them.
> 
> The stringop overread is odd, because another one of them is
> 
>    fs/qnx4/dir.c: In function ‘qnx4_readdir’:
>    fs/qnx4/dir.c:51:32: error: ‘strnlen’ specified bound 48 exceeds
> source size 16 [-Werror=stringop-overread]
>       51 |                         size = strnlen(de->di_fname, size);
>          |                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> but I'm not seeing why that one happens on sparc64, but not on arm64
> or x86-64. There doesn't seem to be anything architecture-specific
> anywhere in that area.
> 
> Funky.
> 
> Davem - attached patch compiles cleanly for me, but I'm not sure it's
> necessarily the right thing to do, and I didn't check the code
> generation. Maybe it screws up. Can somebody test on sparc64 and
> perhaps think about it more than I did?
> 
>                Linus

>  arch/sparc/kernel/mdesc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c
> index 8e645ddac58e..30f171b7b00c 100644
> --- a/arch/sparc/kernel/mdesc.c
> +++ b/arch/sparc/kernel/mdesc.c
> @@ -39,6 +39,7 @@ struct mdesc_hdr {
>  	u32	node_sz; /* node block size */
>  	u32	name_sz; /* name block size */
>  	u32	data_sz; /* data block size */
> +	char	data[];
>  } __attribute__((aligned(16)));
>  
>  struct mdesc_elem {
> @@ -612,7 +613,7 @@ EXPORT_SYMBOL(mdesc_get_node_info);
>  
>  static struct mdesc_elem *node_block(struct mdesc_hdr *mdesc)
>  {
> -	return (struct mdesc_elem *) (mdesc + 1);
> +	return (struct mdesc_elem *) mdesc->data;
>  }
>  
>  static void *name_block(struct mdesc_hdr *mdesc)