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Date:   Fri, 23 Sep 2016 10:38:37 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     "danielmentz@...gle.com" <danielmentz@...gle.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Vineet Gupta" <Vineet.Gupta1@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: modules still have .debug_* (was Re: [PATCH 0/3] ARC unwinder
 switch to .eh_frame)

Hi Daniel,

On Thu, 2016-09-22 at 15:37 -0700, Daniel Mentz wrote:
> On Thu, Sep 22, 2016 at 1:59 PM, Vineet Gupta
> <Vineet.Gupta1@...opsys.com> wrote:
> > 
> > Hi Daniel,
> > 
> > On 09/19/2016 06:21 PM, Daniel Mentz wrote:
> > > 
> > > I confirmed that the .eh_frame section is present and that the
> > > .debug_frame section is absent. I also verified that the file size of
> > > the .ko files are small enough for our embedded platform and that
> > > unnecessary sections like .debug_info, .debug_line, .debug_str etc.
> > > are also absent.
> > 
> > BTW it seems with my latest set of patches, modules still have .debug_*.
> > Can you double check if your tree still has the interim patch which added a linker
> > script for modules to strip out .debug_*
> > 
> > http://lists.infradead.org/pipermail/linux-snps-arc/2016-September/001483.html
> 
> Hi Vineet,
> 
> Sorry, that was a misunderstanding. Buildroot routinely runs the strip
> command on .ko files before installing them on the target. I was only
> looking at the .ko files *after* running the strip command. No, the
> interim patch was not in my tree.

Well are you sure buildroot really touches modules in Linux kernel build folder?
Buildroot just runs a simple "make" command in "output/build/linux-x.y".

And only on installation step Buildroot strips binaries in "output/target" folder.
Moreover starting from that commit
https://git.buildroot.net/buildroot/commit/?id=10c4d27aef4dca01572cfc8146cbfd194a1a85e4
even on Linux installation step Buildroot reuses kernel's module stripping infrastructure
but again that happens only on target.

Just in case that's what I see when building MSDOSFS as module.

In build folder:
----------------------------->8-------------------------------
arc-linux-readelf -S build/linux-4.7.3/fs/fat/msdos.ko
There are 38 section headers, starting at offset 0x2a630:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .note.gnu.build-i NOTE            00000000 000034 000024 00   A  0   0  4
  [ 2] .text             PROGBITS        00000000 000058 0013a8 00  AX  0   0  4
  [ 3] .rela.text        RELA            00000000 01c774 000600 0c   I 35   2  4
  [ 4] .init.text        PROGBITS        00000000 001400 000010 00  AX  0   0  4
  [ 5] .rela.init.text   RELA            00000000 01cd74 000018 0c   I 35   4  4
  [ 6] .exit.text        PROGBITS        00000000 001410 000010 00  AX  0   0  4
  [ 7] .rela.exit.text   RELA            00000000 01cd8c 000018 0c   I 35   6  4
  [ 8] .rodata           PROGBITS        00000000 001440 000100 00   A  0   0 64
  [ 9] .rela.rodata      RELA            00000000 01cda4 000078 0c   I 35   8  4
  [10] .modinfo          PROGBITS        00000000 001540 000090 00   A  0   0  4
  [11] .rodata.str1.4    PROGBITS        00000000 0015d0 000030 01 AMS  0   0  4
  [12] .data             PROGBITS        00000000 001600 00002c 00  WA  0   0  4
  [13] .rela.data        RELA            00000000 01ce1c 000030 0c   I 35  12  4
  [14] .gnu.linkonce.thi PROGBITS        00000000 001640 000140 00  WA  0   0 64
  [15] .rela.gnu.linkonc RELA            00000000 01ce4c 00000c 0c   I 35  14  4
  [16] .tdata            PROGBITS        00000000 001780 000000 00 WAT  0   0  1
  [17] .tbss             NOBITS          00000000 001780 000000 00 WAT  0   0  1
  [18] .bss              NOBITS          00000000 001780 000000 00  WA  0   0  1
  [19] .comment          PROGBITS        00000000 001780 000078 01  MS  0   0  1
  [20] .note.GNU-stack   PROGBITS        00000000 0017f8 000000 00      0   0  1
  [21] .debug_aranges    PROGBITS        00000000 0017f8 000048 00      0   0  1
  [22] .rela.debug_arang RELA            00000000 01ce58 00003c 0c   I 35  21  4
  [23] .debug_info       PROGBITS        00000000 001840 00eaa9 00      0   0  1
  [24] .rela.debug_info  RELA            00000000 01ce94 00a53c 0c   I 35  23  4
  [25] .debug_abbrev     PROGBITS        00000000 0102e9 0008b3 00      0   0  1
  [26] .debug_line       PROGBITS        00000000 010b9c 001d4d 00      0   0  1
  [27] .rela.debug_line  RELA            00000000 0273d0 001818 0c   I 35  26  4
  [28] .debug_frame      PROGBITS        00000000 0128ec 0002d8 00      0   0  4
  [29] .rela.debug_frame RELA            00000000 028be8 000168 0c   I 35  28  4
  [30] .debug_str        PROGBITS        00000000 012bc4 008485 01  MS  0   0  1
  [31] .debug_loc        PROGBITS        00000000 01b049 000b49 00      0   0  1
  [32] .rela.debug_loc   RELA            00000000 028d50 001308 0c   I 35  31  4
  [33] .debug_ranges     PROGBITS        00000000 01bb92 0001f8 00      0   0  1
  [34] .rela.debug_range RELA            00000000 02a058 000480 0c   I 35  33  4
  [35] .symtab           SYMTAB          00000000 01bd8c 0005e0 10     36  53  4
  [36] .strtab           STRTAB          00000000 01c36c 000407 00      0   0  1
  [37] .shstrtab         STRTAB          00000000 02a4d8 000157 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  p (processor specific)
----------------------------->8-------------------------------

On target:
----------------------------->8-------------------------------
arc-linux-readelf -S target/lib/modules/4.7.3/kernel/fs/fat/msdos.ko 
There are 24 section headers, starting at offset 0x28e0:

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .note.gnu.build-i NOTE            00000000 000034 000024 00   A  0   0  4
  [ 2] .text             PROGBITS        00000000 000058 0013a8 00  AX  0   0  4
  [ 3] .rela.text        RELA            00000000 002128 000600 0c   I 21   2  4
  [ 4] .init.text        PROGBITS        00000000 001400 000010 00  AX  0   0  4
  [ 5] .rela.init.text   RELA            00000000 002728 000018 0c   I 21   4  4
  [ 6] .exit.text        PROGBITS        00000000 001410 000010 00  AX  0   0  4
  [ 7] .rela.exit.text   RELA            00000000 002740 000018 0c   I 21   6  4
  [ 8] .rodata           PROGBITS        00000000 001440 000100 00   A  0   0 64
  [ 9] .rela.rodata      RELA            00000000 002758 000078 0c   I 21   8  4
  [10] .modinfo          PROGBITS        00000000 001540 000090 00   A  0   0  4
  [11] .rodata.str1.4    PROGBITS        00000000 0015d0 000030 01 AMS  0   0  4
  [12] .data             PROGBITS        00000000 001600 00002c 00  WA  0   0  4
  [13] .rela.data        RELA            00000000 0027d0 000030 0c   I 21  12  4
  [14] .gnu.linkonce.thi PROGBITS        00000000 001640 000140 00  WA  0   0 64
  [15] .rela.gnu.linkonc RELA            00000000 002800 00000c 0c   I 21  14  4
  [16] .tdata            PROGBITS        00000000 001780 000000 00 WAT  0   0  1
  [17] .tbss             NOBITS          00000000 001780 000000 00 WAT  0   0  1
  [18] .bss              NOBITS          00000000 001780 000000 00  WA  0   0  1
  [19] .comment          PROGBITS        00000000 001780 000078 01  MS  0   0  1
  [20] .note.GNU-stack   PROGBITS        00000000 0017f8 000000 00      0   0  1
  [21] .symtab           SYMTAB          00000000 0017f8 000540 10     22  43  4
  [22] .strtab           STRTAB          00000000 001d38 0003ed 00      0   0  1
  [23] .shstrtab         STRTAB          00000000 00280c 0000d3 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  p (processor specific)
----------------------------->8-------------------------------

-Alexey

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