From mboxrd@z Thu Jan  1 00:00:00 1970
From: f.fainelli@gmail.com (Florian Fainelli)
Date: Wed, 26 Apr 2017 16:28:44 -0700
Subject: Duplicate .plt sections warning with CONFIG_ARM_MODULE_PLTS
In-Reply-To: <CAKv+Gu8h9-MRKm6gxn79voW6sR0EQ5e2zNLRwh2vfew8Sfr42w@mail.gmail.com>
References: <1fb01fb6-3306-1d96-1da0-5b732555dfaf@gmail.com>
 <CAKv+Gu8h9-MRKm6gxn79voW6sR0EQ5e2zNLRwh2vfew8Sfr42w@mail.gmail.com>
Message-ID: <6bd5005b-61d1-d2f9-fb0f-5ce200bfffd9@gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 04/26/2017 12:33 AM, Ard Biesheuvel wrote:
> On 26 April 2017 at 00:35, Florian Fainelli <f.fainelli@gmail.com> wrote:
>> Hi Ard,
>>
>> While using CONFIG_ARM_MODULES_PLTS=y along with a large kernel module,
>> I was able to have the kernel/module.c::add_sect_attrs() to complain
>> about duplicate .plt sections found, each section gets its own sysfs
>> attribute created under /sys/module/<modname>/sections/<sectname>
>>
>> And indeed the module has the following section headers and contents
>> (see below). Is this something that looks legit or should we patch
>> kernel/module.c to detect such duplicates and generate unique sysfs
>> attribute section names instead? There does not appear to be any
>> functional issue with that.
>>
> 
> Does it happen with a clean build?

Yes it does, it was not quite the problem see below.

> The .plt/.init.plt sections are
> declared in the linker scripts, and so no module object should have
> any such sections until the relocatable link occurs that combines them
> all into a .ko, and it is at this point that these sections are
> declared.

It turned out that the module build I was debugging was built in a
strange way with a first step producing foo.o_shipped, which (semi)
manually pulling into the kernel's linker scripts, and then,
foo.o_shipped was used to link foo.ko which then again got the linker
scripts from the kernel. This is how we ended up with the two .plt and
two .init.plt sections being present in foo.ko.

Thanks!

> 
> 
>> Thanks!
>>
>> Contents of section .plt:
>>  0000 00                                   .
>> Contents of section .init.plt:
>>  0001 00                                   .
>> Contents of section .plt:
>>  0000 00
>>
>> Section Headers:
>>   [Nr] Name              Type            Addr     Off    Size   ES Flg
>> Lk Inf Al
>>   [ 0]                   NULL            00000000 000000 000000 00
>> 0   0  0
>>   [ 1] .text             PROGBITS        00000000 000034 48d360 00  AX
>> 0   0  4
>>   [ 2] .rel.text         REL             00000000 68d0c4 14a980 08
>> 48   1  4
>>   [ 3] .text.unlikely    PROGBITS        00000000 48d394 001a30 00  AX
>> 0   0  4
>>   [ 4] .rel.text.unlikel REL             00000000 7d7a44 000700 08
>> 48   3  4
>>   [ 5] .rodata           PROGBITS        00000000 48edc8 0b1fa4 00   A
>> 0   0  8
>>   [ 6] .rel.rodata       REL             00000000 7d8144 025938 08
>> 48   5  4
>>   [ 7] .rodata.str1.1    PROGBITS        00000000 540d6c 10b88a 01 AMS
>> 0   0  1
>>   [ 8] .ARM.extab.text.u PROGBITS        00000000 64c5f8 000060 00   A
>> 0   0  4
>>   [ 9] .ARM.exidx.text.u ARM_EXIDX       00000000 64c658 000090 00  AL
>> 3   0  4
>>   [10] .rel.ARM.exidx.te REL             00000000 7fda7c 000148 08
>> 48   9  4
>>   [11] __ksymtab_strings PROGBITS        00000000 64c6e8 00da64 00   A
>> 0   0  1
>>   [12] .modinfo          PROGBITS        00000000 65a14c 0000a0 00   A
>> 0   0  4
>>   [13] __param           PROGBITS        00000000 65a1ec 000020 00   A
>> 0   0  4
>>   [14] .rel__param       REL             00000000 7fdbc4 000030 08
>> 48  13  4
>>   [15] .alt.smp.init     PROGBITS        00000000 65a20c 000028 00   A
>> 0   0  4
>>   [16] .rel.alt.smp.init REL             00000000 7fdbf4 000028 08
>> 48  15  4
>>   [17] __ex_table        PROGBITS        00000000 65a238 000008 00   A
>> 0   0  8
>>   [18] .rel__ex_table    REL             00000000 7fdc1c 000010 08
>> 48  17  4
>>   [19] .ARM.extab        PROGBITS        00000000 65a240 002730 00   A
>> 0   0  4
>>   [20] .ARM.exidx        ARM_EXIDX       00000000 65c970 01b658 00  AL
>> 1   0  4
>>   [21] .rel.ARM.exidx    REL             00000000 7fdc2c 01f798 08
>> 48  20  4
>>   [22] __versions        PROGBITS        00000000 677fc8 001840 00   A
>> 0   0  4
>>   [23] .note.gnu.build-i NOTE            00000000 679808 000048 00   A
>> 0   0  4
>>   [24] .plt              PROGBITS        00000000 679850 000001 00  WA
>> 0   0  1
>>   [25] .init.plt         PROGBITS        00000001 679851 000001 00  WA
>> 0   0  1
>>   [26] .plt              PROGBITS        00000000 679852 000001 00  WA
>> 0   0  1
>>   [27] .data             PROGBITS        00000000 679854 0039e8 00  WA
>> 0   0  4
>>   [28] .rel.data         REL             00000000 81d3c4 001ca0 08
>> 48  27  4
>>   [29] .init.plt         PROGBITS        00000000 67d23c 000001 00  WA
>> 0   0  1
>>   [30] .gnu.linkonce.thi PROGBITS        00000000 67d240 000168 00  WA
>> 0   0  4
>>   [31] .rel.gnu.linkonce REL             00000000 81f064 000010 08
>> 48  30  4
>>   [32] .bss              NOBITS          00000000 67d3a8 04dbac 00  WA
>> 0   0  8
>>   [33] .comment          PROGBITS        00000000 67d3a8 009106 01  MS
>> 0   0  1
>>   [34] .note.GNU-stack   PROGBITS        00000000 6864ae 000000 00   X
>> 0   0  1
>>   [35] .ARM.attributes   ARM_ATTRIBUTES  00000000 6864ae 000031 00
>> 0   0  1
>>   [36] __ksymtab         PROGBITS        00000000 6864e0 0036b8 00   A
>> 0   0  4
>>   [37] .rel__ksymtab     REL             00000000 81f074 006d70 08
>> 48  36  4
>>   [38] __kcrctab         PROGBITS        00000000 689b98 001b5c 00   A
>> 0   0  4
>>   [39] .rel__kcrctab     REL             00000000 825de4 0036b8 08
>> 48  38  4
>>   [40] .debug_info       PROGBITS        00000000 68b6f4 000490 00
>> 0   0  1
>>   [41] .rel.debug_info   REL             00000000 82949c 000408 08
>> 48  40  4
>>   [42] .debug_abbrev     PROGBITS        00000000 68bb84 0000f8 00
>> 0   0  1
>>   [43] .debug_aranges    PROGBITS        00000000 68bc7c 000018 00
>> 0   0  1
>>   [44] .rel.debug_arange REL             00000000 8298a4 000008 08
>> 48  43  4
>>   [45] .debug_line       PROGBITS        00000000 68bc94 000190 00
>> 0   0  1
>>   [46] .debug_str        PROGBITS        00000000 68be24 000900 01  MS
>> 0   0  1
>>   [47] .shstrtab         STRTAB          00000000 68c724 0001cd 00
>> 0   0  1
>>   [48] .symtab           SYMTAB          00000000 8298ac 0ffc50 10
>> 49 49732  4
>>   [49] .strtab           STRTAB          00000000 9294fc 0f5791 00
>> 0   0  1
>>
>> --
>> Florian


-- 
Florian