linux-kernel - Re: [PATCH] kbuild: modpost: Warn about references from rodata to _

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Date:   Fri, 30 Jun 2017 19:59:24 -0400
From:   Rob Clark <robdclark@...il.com>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <mmarek@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kbuild@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH] kbuild: modpost: Warn about references from rodata to
 __init text

On Fri, Jun 30, 2017 at 6:58 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> If we have a structure that's marked const it will be placed
> into the .rodata section but it could reference an init section
> function. Include the read only data section in the check we have
> for read/write data sections referencing init sections so we can
> find this class of problems. This exposes quite a few places
> where const marked structures are referencing __init functions and
> __init data that we were previously ignoring.
>
> Cc: Rob Clark <robdclark@...il.com>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>
> Making this change leads to quite a few other errors even on the
> multi_v7_defconfig for ARM[1]. I still need to do a build of the
> allmodconfig to see how many other errors there, but it seems to
> be quite a few. I suppose those will need to be fixed before we can
> merge this?

thanks.. the explosions you get with these mistakes when building
drivers as modules in a distro kernel config are quite "fun" to
debug..

I'm not quite sure about the rules for whether merging this would
count as a regression, but I would argue those drivers are already
broken, just no one noticed yet.  Similar to when a new gcc gets more
clever about detecting bugs.  So I wouldn't be against merging this
first to force drivers to fix their crap ;-)

BR,
-R

> [1] https://www.irccloud.com/pastebin/zzqfWGQY/
>
>  scripts/mod/modpost.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 48397feb08fb..4f2be5c6727d 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -903,7 +903,7 @@ static void check_section(const char *modname, struct elf_info *elf,
>  #define ALL_INIT_SECTIONS INIT_SECTIONS, ALL_XXXINIT_SECTIONS
>  #define ALL_EXIT_SECTIONS EXIT_SECTIONS, ALL_XXXEXIT_SECTIONS
>
> -#define DATA_SECTIONS ".data", ".data.rel"
> +#define DATA_SECTIONS ".rodata", ".data", ".data.rel"
>  #define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \
>                 ".kprobes.text", ".cpuidle.text"
>  #define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>