Date:   Tue, 15 Sep 2020 11:30:16 +0200
From:   peterz@...radead.org
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, mark@...mp.org
Subject: Re: Static call dependency on libelf version?

On Tue, Sep 15, 2020 at 12:50:54AM -0700, Hugh Dickins wrote:
> This is just an FYI written from a position of ignorance: I may
> have got it wrong, and my build environment too piecemeal to matter
> to anyone else; but what I saw was weird enough to be worth mentioning,
> in case it saves someone some time.
> 
> I usually build and test on mmotm weekly rather linux-next daily.
> No problem with 5.9-rc3-mm1 from 2020-09-04, nor with 5.9-rc5, but
> (on two machines) 5.9-rc5-mm1 from 2020-09-13 could not link vmlinux:
> 
>   AR      init/built-in.a
>   LD      vmlinux.o
> ld: warning: init/main.o has a corrupt section with a size (7472747368732e00) larger than the file size
> ld: warning: init/main.o has a corrupt section with a size (7472747368732e00) larger than the file size
> ld: warning: init/main.o has a corrupt section with a size (7472747368732e00) larger than the file size
> ld: warning: init/main.o has a corrupt section with a size (7472747368732e00) larger than the file size
> ld: init/built-in.a: member init/main.o in archive is not an object
> make[1]: *** [vmlinux] Error 1
> make: *** [__sub-make] Error 2
> 
> On the third machine, a more recent installation, but using the same
> gcc and the same binutils, I could build the same config successfully.
> init/main.o was the same size on each (49216 bytes), but diff of hd
> of the good against the bad showed:
> 
> 2702,2709c2702,2709
> < 00bfc0 000001db 00000001 00000003 00000000  >................<
> < 00bfd0 00000000 00000000 0000b316 00000000  >................<
> < 00bfe0 00000018 00000000 00000000 00000000  >................<
> < 00bff0 00000001 00000000 00000008 00000000  >................<
> < 00c000 000001ee 00000004 00000040 00000000  >........@.......<
> < 00c010 00000000 00000000 0000b330 00000000  >........0.......<
> < 00c020 00000090 00000000 0000002d 00000030  >........-...0...<
> < 00c030 00000008 00000000 00000018 00000000  >................<
> ---
> > 00bfc0 00000000 00000000 000001f1 00000000  >................<
> > 00bfd0 79732e00 6261746d 74732e00 62617472  >..symtab..strtab<
> > 00bfe0 68732e00 74727473 2e006261 616c6572  >..shstrtab..rela<
> > 00bff0 7865742e 722e0074 2e616c65 61746164  >.text..rela.data<
> > 00c000 73622e00 722e0073 5f616c65 6172745f  >..bss..rela__tra<
> > 00c010 6f706563 73746e69 7274705f 722e0073  >cepoints_ptrs..r<
> > 00c020 2e616c65 74617473 635f6369 2e6c6c61  >ela.static_call.<
> > 00c030 74786574 65722e00 692e616c 2e74696e  >text..rela.init.<
> 
> and 217 other .os in the build tree also "corrupted".
> 
> CONFIG_HAVE_STATIC_CALL=y
> CONFIG_HAVE_STATIC_CALL_INLINE=y
> stand out as new in the .config for 5.9-rc5-mm1, and references
> to objtool in static_call.h and static_call_types.h took me to
> tools/objtool/Makefile, with its use of libelf.
> 
> I've copied over files of the newer libelf (0.168) to the failing
> machines, which are now building the 5.9-rc5-mm1 vmlinux correctly.
> 
> It looks as if CONFIG_HAVE_STATIC_CALL=y depends on a newer libelf
> than I had before (0.155), and should either insist on a minimum
> version, or else be adjusted to work with older versions.

Hurmph, I have no idea how this happened; clearly none of my machines
have this older libelf :/ (the machines I use most seem to be on 0.180).

I'm also not sure what static_call is doing different from say orc
data generation. Both create and fill sections in similar ways.

Mark, do you have any idea?

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