linux-kernel - Re: [PATCH v2 3/5] mips: Print the kernel virtual mem layout on debugging

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Date:   Wed, 8 May 2019 01:36:07 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Paul Burton <paul.burton@...s.com>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Bogendoerfer <tbogendoerfer@...e.de>,
        Huacai Chen <chenhc@...ote.com>,
        Stefan Agner <stefan@...er.ch>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Juergen Gross <jgross@...e.com>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] mips: Print the kernel virtual mem layout on
 debugging

Hello Paul

On Mon, May 06, 2019 at 07:14:21PM +0000, Paul Burton wrote:
> Hi Serge,
> 
> On Fri, May 03, 2019 at 08:50:39PM +0300, Serge Semin wrote:
> > It is useful at least for debugging to have the kernel virtual
> > memory layout printed at boot time so to have the full information
> > about the booted kernel. Make the printing optional and available
> > only when DEBUG_KERNEL config is enabled so not to leak a sensitive
> > kernel information.
> > 
> > Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> > ---
> >  arch/mips/mm/init.c | 49 +++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> 
> FYI the rest of the series is in mips-next, but I left this one out
> because it gives me compile errors for 64r6el_defconfig:
> 
> In file included from ./include/linux/printk.h:7,
>                  from ./include/linux/kernel.h:15,
>                  from ./include/asm-generic/bug.h:18,
>                  from ./arch/mips/include/asm/bug.h:42,
>                  from ./include/linux/bug.h:5,
>                  from arch/mips/mm/init.c:11:
> arch/mips/mm/init.c: In function ‘mem_print_kmap_info’:
> ./include/linux/kern_levels.h:5:18: error: format ‘%ld’ expects argument of type ‘long int’, but argument 4 has type ‘long long unsigned int’ [-Werror=format=]
>  #define KERN_SOH "\001"  /* ASCII Start Of Header */
>                   ^~~~~~
> ./include/linux/kern_levels.h:13:21: note: in expansion of macro ‘KERN_SOH’
>  #define KERN_NOTICE KERN_SOH "5" /* normal but significant condition */
>                      ^~~~~~~~
> ./include/linux/printk.h:307:9: note: in expansion of macro ‘KERN_NOTICE’
>   printk(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)
>          ^~~~~~~~~~~
> arch/mips/mm/init.c:69:2: note: in expansion of macro ‘pr_notice’
>   pr_notice("Kernel virtual memory layout:\n"
>   ^~~~~~~~~
> arch/mips/mm/init.c:70:39: note: format string is defined here
>      "    lowmem  : 0x%px - 0x%px  (%4ld MB)\n"
>                                     ~~~^
>                                     %4lld
> In file included from ./arch/mips/include/asm/bug.h:5,
>                  from ./include/linux/bug.h:5,
>                  from arch/mips/mm/init.c:11:
> In function ‘mem_print_kmap_info’,
>     inlined from ‘mem_init’ at arch/mips/mm/init.c:530:2:
> ./include/linux/compiler.h:344:38: error: call to ‘__compiletime_assert_99’ declared with attribute error: BUILD_BUG_ON failed: FIXADDR_TOP < PAGE_OFFSET
>   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>                                       ^
> ./include/linux/compiler.h:325:4: note: in definition of macro ‘__compiletime_assert’
>     prefix ## suffix();    \
>     ^~~~~~
> ./include/linux/compiler.h:344:2: note: in expansion of macro ‘_compiletime_assert’
>   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>   ^~~~~~~~~~~~~~~~~~~
> ./include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’
>  #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>                                      ^~~~~~~~~~~~~~~~~~
> ./include/linux/build_bug.h:50:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
>   BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
>   ^~~~~~~~~~~~~~~~
> arch/mips/mm/init.c:99:2: note: in expansion of macro ‘BUILD_BUG_ON’
>   BUILD_BUG_ON(FIXADDR_TOP < PAGE_OFFSET);
>   ^~~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[3]: *** [scripts/Makefile.build:278: arch/mips/mm/init.o] Error 1
> make[2]: *** [scripts/Makefile.build:489: arch/mips/mm] Error 2
> 
> Thanks,
>     Paul

Thanks for the report regarding this issue. I actually thought I tested the patch
being buildable for 64bit systems. It turns out I didn't.(

Should I resend the fixed patch as a separate v3 one In-Reply-to this v2 patch
or resubmit the patchset with cover-letter and only the fixed patch being there?

Cheers,
-Sergey