[RFC][PATCHSET v2] allowing exports in *.S

[Al Viro <viro@ZenIV.linux.org.uk>]

On Fri, Jan 29, 2016 at 07:17:44PM +0000, Al Viro wrote:

> 	The policy wrt exports right now is "put it next to the definition
> of object being exported, unless it's in assembler".  The reasons for having
> an export near the definition are obvious - it's easier to keep things
> in sync that way, the fact that function can be called by modules is
> obvious without grepping through the entire tree, etc.
> 
> 	The major exception is for things defined in assembler - exports
> of those are kept in arch/*/*/*ksyms*.c.  The reason is that EXPORT_SYMBOL
> and friends can't be used from assembler; all the reasons to keep them
> with definitions still apply, but we simply can't do that.

[snip]

> The first patch allows to export safely from lib-*, the second one adds
> asm-generic/export.h, usable as-is for almost all architectures.  The only
> exceptions are 64bit x86, which wants unusually strong alignment for
> struct kernel_symbol and m68k, which wants only 16bit alignements for pointers
> (and for struct kernel_symbol as well).  Such an architecture can add
> asm/export.h that defines a couple of macros (KSYM_ALIGN and KCRC_ALIGN)
> and includes <asm-generic/export.h>.  Normally you only need to add
> generic-y += export.h to asm/Kbuild; of course, if you don't put any exports
> into asm files, you don't need to do anything at all.

Turns out that I'd missed another oddity on some architectures.  ia64 and
parisc64 compile the kernel with pointers to functions actually pointing
to function descriptors and, unlike ppc64, need to have that spelled out
in asm literals (fptr@(foo) on ia64 and P%foo on parisc; foo itself would
refer to the function entry point, while on ppc64 foo would refer to descriptor
and .foo - to the entry point).

First of all, it means that exporting foo requires knowing whether it's
a function or not; C compiler has that information, but for assembler we
have to supply it manually.  Solution: EXPORT_DATA_SYMBOL{,_GPL} for exporting
non-functions (they are seriously outnumbered by function exports, so I kept
the EXPORT_SYMBOL{,_GPL} for those).  On normal architectures either can
be used, on ia64 and parisc we need to make sure to use the right one.

Another thing is that we need to know how to get from function name to the
descriptor for such architectures.  That's handled by defining KSYM_FUNC(name)
in asm/export.h.

Other changes since the previous posting:
	* unbreak linking of arch/ia64/hp/sim/boot/bootloader; it ended
up picking everything in arch/ia64/lib that contained some exports, and
some of those require stuff from the kernel proper.  Easy to fix, fortunately.
	* fix kbuild-related braino that ended up with the lib-ksyms.o
rebuilt for no reason.
	* fixes for assorted brainos picked by buildbot folded in.
	* ACKs applied (with the exception of the second patch in series -
asm-generic/export.h differences are considerable and I don't think that
ACK to the original variant automatically applies to the new one).

> Of course, we don't have to move all exports at once (or move them at all);
> it's not a flagday conversion.  The whole series so far can be picked at
> git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.asm-exports;
> I'll post individual patches in followups.
 
If everyone (including kbuild folks) is OK with the arch-independent parts of
this series, I'd like to put the first two commits into never-rebased branch
so that individual architecture trees could pull that and apply the
corresponding arch-dependent stuff on top of that; going that way would
minimize the amount of conflicts that would need to be dealt with during
this cycle, but it obviously depends on those first two commits being
acceptable to everyone.  Please, review and comment.

Shortlog:
Al Viro (13):
      [kbuild] handle exports in lib-y objects reliably
      EXPORT_SYMBOL() for asm
      x86: move exports to actual definitions
      alpha: move exports to actual definitions
      m68k: move exports to definitions
      s390: move exports to definitions
      arm: move exports to definitions
      ppc: move exports to definitions
      ppc: get rid of unreachable abs() implementation
      sparc: move exports to definitions
      [sparc] unify 32bit and 64bit string.h
      sparc32: debride memcpy.S a bit
      ia64: move exports to definitions

Diffstat:
 arch/alpha/include/asm/Kbuild         |   1 +
 arch/alpha/kernel/Makefile            |   2 +-
 arch/alpha/kernel/alpha_ksyms.c       | 102 -------------------
 arch/alpha/kernel/machvec_impl.h      |   6 +-
 arch/alpha/kernel/setup.c             |   1 +
 arch/alpha/lib/callback_srm.S         |   5 +
 arch/alpha/lib/checksum.c             |   3 +
 arch/alpha/lib/clear_page.S           |   3 +-
 arch/alpha/lib/clear_user.S           |   2 +
 arch/alpha/lib/copy_page.S            |   3 +-
 arch/alpha/lib/copy_user.S            |   3 +
 arch/alpha/lib/csum_ipv6_magic.S      |   2 +
 arch/alpha/lib/csum_partial_copy.c    |   2 +
 arch/alpha/lib/dec_and_lock.c         |   2 +
 arch/alpha/lib/divide.S               |   3 +
 arch/alpha/lib/ev6-clear_page.S       |   3 +-
 arch/alpha/lib/ev6-clear_user.S       |   3 +-
 arch/alpha/lib/ev6-copy_page.S        |   3 +-
 arch/alpha/lib/ev6-copy_user.S        |   3 +-
 arch/alpha/lib/ev6-csum_ipv6_magic.S  |   2 +
 arch/alpha/lib/ev6-divide.S           |   3 +
 arch/alpha/lib/ev6-memchr.S           |   3 +-
 arch/alpha/lib/ev6-memcpy.S           |   3 +-
 arch/alpha/lib/ev6-memset.S           |   7 +-
 arch/alpha/lib/ev67-strcat.S          |   3 +-
 arch/alpha/lib/ev67-strchr.S          |   3 +-
 arch/alpha/lib/ev67-strlen.S          |   3 +-
 arch/alpha/lib/ev67-strncat.S         |   3 +-
 arch/alpha/lib/ev67-strrchr.S         |   3 +-
 arch/alpha/lib/fpreg.c                |   7 ++
 arch/alpha/lib/memchr.S               |   3 +-
 arch/alpha/lib/memcpy.c               |   5 +-
 arch/alpha/lib/memmove.S              |   3 +-
 arch/alpha/lib/memset.S               |   7 +-
 arch/alpha/lib/strcat.S               |   2 +
 arch/alpha/lib/strchr.S               |   3 +-
 arch/alpha/lib/strcpy.S               |   3 +-
 arch/alpha/lib/strlen.S               |   3 +-
 arch/alpha/lib/strncat.S              |   3 +-
 arch/alpha/lib/strncpy.S              |   3 +-
 arch/alpha/lib/strrchr.S              |   3 +-
 arch/arm/include/asm/Kbuild           |   1 +
 arch/arm/kernel/Makefile              |   2 +-
 arch/arm/kernel/armksyms.c            | 183 ----------------------------------
 arch/arm/kernel/entry-ftrace.S        |   3 +
 arch/arm/kernel/head.S                |   3 +
 arch/arm/kernel/smccc-call.S          |   3 +
 arch/arm/lib/ashldi3.S                |   3 +
 arch/arm/lib/ashrdi3.S                |   3 +
 arch/arm/lib/bitops.h                 |   5 +
 arch/arm/lib/bswapsdi2.S              |   3 +
 arch/arm/lib/clear_user.S             |   4 +
 arch/arm/lib/copy_from_user.S         |   2 +
 arch/arm/lib/copy_page.S              |   2 +
 arch/arm/lib/copy_to_user.S           |   4 +
 arch/arm/lib/csumipv6.S               |   3 +-
 arch/arm/lib/csumpartial.S            |   2 +
 arch/arm/lib/csumpartialcopy.S        |   1 +
 arch/arm/lib/csumpartialcopygeneric.S |   2 +
 arch/arm/lib/csumpartialcopyuser.S    |   1 +
 arch/arm/lib/delay.c                  |   2 +
 arch/arm/lib/div64.S                  |   2 +
 arch/arm/lib/findbit.S                |   9 ++
 arch/arm/lib/getuser.S                |   9 ++
 arch/arm/lib/io-readsb.S              |   2 +
 arch/arm/lib/io-readsl.S              |   2 +
 arch/arm/lib/io-readsw-armv3.S        |   3 +-
 arch/arm/lib/io-readsw-armv4.S        |   2 +
 arch/arm/lib/io-writesb.S             |   2 +
 arch/arm/lib/io-writesl.S             |   2 +
 arch/arm/lib/io-writesw-armv3.S       |   2 +
 arch/arm/lib/io-writesw-armv4.S       |   2 +
 arch/arm/lib/lib1funcs.S              |   9 ++
 arch/arm/lib/lshrdi3.S                |   3 +
 arch/arm/lib/memchr.S                 |   2 +
 arch/arm/lib/memcpy.S                 |   3 +
 arch/arm/lib/memmove.S                |   2 +
 arch/arm/lib/memset.S                 |   3 +
 arch/arm/lib/memzero.S                |   2 +
 arch/arm/lib/muldi3.S                 |   3 +
 arch/arm/lib/putuser.S                |   5 +
 arch/arm/lib/strchr.S                 |   2 +
 arch/arm/lib/strrchr.S                |   2 +
 arch/arm/lib/uaccess_with_memcpy.c    |   3 +
 arch/arm/lib/ucmpdi2.S                |   3 +
 arch/arm/mach-imx/Makefile            |   1 -
 arch/arm/mach-imx/ssi-fiq-ksym.c      |  20 ----
 arch/arm/mach-imx/ssi-fiq.S           |   7 +-
 arch/ia64/hp/sim/boot/Makefile        |   2 +-
 arch/ia64/include/asm/export.h        |   3 +
 arch/ia64/kernel/entry.S              |   3 +
 arch/ia64/kernel/esi_stub.S           |   2 +
 arch/ia64/kernel/head.S               |   2 +
 arch/ia64/kernel/ia64_ksyms.c         |  94 +----------------
 arch/ia64/kernel/ivt.S                |   2 +
 arch/ia64/kernel/pal.S                |   7 ++
 arch/ia64/kernel/setup.c              |   4 +
 arch/ia64/lib/Makefile                |   8 +-
 arch/ia64/lib/clear_page.S            |   2 +
 arch/ia64/lib/clear_user.S            |   2 +
 arch/ia64/lib/copy_page.S             |   2 +
 arch/ia64/lib/copy_page_mck.S         |   2 +
 arch/ia64/lib/copy_user.S             |   2 +
 arch/ia64/lib/flush.S                 |   2 +
 arch/ia64/lib/idiv32.S                |   2 +
 arch/ia64/lib/idiv64.S                |   2 +
 arch/ia64/lib/ip_fast_csum.S          |   3 +
 arch/ia64/lib/memcpy.S                |   2 +
 arch/ia64/lib/memcpy_mck.S            |   3 +
 arch/ia64/lib/memset.S                |   2 +
 arch/ia64/lib/strlen.S                |   2 +
 arch/ia64/lib/strlen_user.S           |   2 +
 arch/ia64/lib/strncpy_from_user.S     |   2 +
 arch/ia64/lib/strnlen_user.S          |   2 +
 arch/ia64/lib/xor.S                   |   5 +
 arch/m68k/include/asm/export.h        |   3 +
 arch/m68k/kernel/Makefile             |   2 +-
 arch/m68k/kernel/m68k_ksyms.c         |  32 ------
 arch/m68k/lib/ashldi3.c               |   4 +
 arch/m68k/lib/ashrdi3.c               |   4 +
 arch/m68k/lib/divsi3.S                |   3 +
 arch/m68k/lib/lshrdi3.c               |   4 +
 arch/m68k/lib/modsi3.S                |   3 +
 arch/m68k/lib/muldi3.c                |   4 +
 arch/m68k/lib/mulsi3.S                |   4 +-
 arch/m68k/lib/udivsi3.S               |   4 +-
 arch/m68k/lib/umodsi3.S               |   4 +-
 arch/powerpc/include/asm/Kbuild       |   1 +
 arch/powerpc/kernel/Makefile          |   4 -
 arch/powerpc/kernel/entry_32.S        |   2 +
 arch/powerpc/kernel/entry_64.S        |   3 +
 arch/powerpc/kernel/epapr_hcalls.S    |   2 +
 arch/powerpc/kernel/fpu.S             |   3 +
 arch/powerpc/kernel/head_32.S         |   5 +
 arch/powerpc/kernel/head_40x.S        |   2 +
 arch/powerpc/kernel/head_44x.S        |   2 +
 arch/powerpc/kernel/head_64.S         |   2 +
 arch/powerpc/kernel/head_8xx.S        |   2 +
 arch/powerpc/kernel/head_fsl_booke.S  |   2 +
 arch/powerpc/kernel/misc.S            |   2 +
 arch/powerpc/kernel/misc_32.S         |  18 ++--
 arch/powerpc/kernel/misc_64.S         |   4 +
 arch/powerpc/kernel/pci-common.c      |   1 +
 arch/powerpc/kernel/pci_32.c          |   2 +
 arch/powerpc/kernel/ppc_ksyms.c       |  39 --------
 arch/powerpc/kernel/ppc_ksyms_32.c    |  61 ------------
 arch/powerpc/kernel/setup_32.c        |   6 ++
 arch/powerpc/kernel/time.c            |   1 +
 arch/powerpc/kernel/vector.S          |   4 +
 arch/powerpc/lib/Makefile             |   2 +-
 arch/powerpc/lib/checksum_32.S        |   4 +
 arch/powerpc/lib/checksum_64.S        |   4 +
 arch/powerpc/lib/copy_32.S            |   5 +
 arch/powerpc/lib/copypage_64.S        |   2 +
 arch/powerpc/lib/copyuser_64.S        |   2 +
 arch/powerpc/lib/hweight_64.S         |   5 +
 arch/powerpc/lib/mem_64.S             |   3 +
 arch/powerpc/lib/memcmp_64.S          |   2 +
 arch/powerpc/lib/memcpy_64.S          |   2 +
 arch/powerpc/lib/ppc_ksyms.c          |  35 -------
 arch/powerpc/lib/string.S             |  10 ++
 arch/powerpc/lib/string_64.S          |   2 +
 arch/powerpc/mm/hash_low_32.S         |   3 +
 arch/powerpc/sysdev/dcr-low.S         |   3 +
 arch/s390/include/asm/Kbuild          |   1 +
 arch/s390/kernel/Makefile             |   2 +-
 arch/s390/kernel/entry.S              |   6 ++
 arch/s390/kernel/mcount.S             |   3 +
 arch/s390/kernel/s390_ksyms.c         |  15 ---
 arch/s390/lib/mem.S                   |   3 +
 arch/sparc/include/asm/Kbuild         |   1 +
 arch/sparc/include/asm/string.h       |  34 +++++++
 arch/sparc/include/asm/string_32.h    |  56 -----------
 arch/sparc/include/asm/string_64.h    |  44 --------
 arch/sparc/kernel/Makefile            |   2 +-
 arch/sparc/kernel/entry.S             |   3 +
 arch/sparc/kernel/head_32.S           |   3 +
 arch/sparc/kernel/head_64.S           |   7 +-
 arch/sparc/kernel/helpers.S           |   2 +
 arch/sparc/kernel/hvcalls.S           |   4 +
 arch/sparc/kernel/sparc_ksyms.c       |  12 +++
 arch/sparc/kernel/sparc_ksyms_32.c    |  31 ------
 arch/sparc/kernel/sparc_ksyms_64.c    |  52 ----------
 arch/sparc/lib/Makefile               |   1 -
 arch/sparc/lib/U1memcpy.S             |   2 +
 arch/sparc/lib/VISsave.S              |   2 +
 arch/sparc/lib/ashldi3.S              |   2 +
 arch/sparc/lib/ashrdi3.S              |   2 +
 arch/sparc/lib/atomic_64.S            |  10 +-
 arch/sparc/lib/bitops.S               |   7 ++
 arch/sparc/lib/blockops.S             |   3 +
 arch/sparc/lib/bzero.S                |   4 +
 arch/sparc/lib/checksum_32.S          |   3 +
 arch/sparc/lib/checksum_64.S          |   2 +
 arch/sparc/lib/clear_page.S           |   3 +
 arch/sparc/lib/copy_in_user.S         |   2 +
 arch/sparc/lib/copy_page.S            |   2 +
 arch/sparc/lib/copy_user.S            |   2 +
 arch/sparc/lib/csum_copy.S            |   3 +
 arch/sparc/lib/divdi3.S               |   2 +
 arch/sparc/lib/ffs.S                  |   3 +
 arch/sparc/lib/hweight.S              |   5 +
 arch/sparc/lib/ipcsum.S               |   2 +
 arch/sparc/lib/ksyms.c                | 165 ------------------------------
 arch/sparc/lib/locks.S                |   5 +
 arch/sparc/lib/lshrdi3.S              |   2 +
 arch/sparc/lib/mcount.S               |   2 +
 arch/sparc/lib/memcmp.S               |   2 +
 arch/sparc/lib/memcpy.S               |  86 +---------------
 arch/sparc/lib/memmove.S              |   2 +
 arch/sparc/lib/memscan_32.S           |   4 +
 arch/sparc/lib/memscan_64.S           |   4 +
 arch/sparc/lib/memset.S               |   3 +
 arch/sparc/lib/muldi3.S               |   2 +
 arch/sparc/lib/strlen.S               |   2 +
 arch/sparc/lib/strncmp_32.S           |   2 +
 arch/sparc/lib/strncmp_64.S           |   2 +
 arch/sparc/lib/xor.S                  |   9 ++
 arch/x86/entry/entry_32.S             |   2 +
 arch/x86/entry/entry_64.S             |   2 +
 arch/x86/entry/thunk_32.S             |   3 +
 arch/x86/entry/thunk_64.S             |   3 +
 arch/x86/include/asm/export.h         |   4 +
 arch/x86/kernel/Makefile              |   4 +-
 arch/x86/kernel/head_32.S             |   2 +
 arch/x86/kernel/head_64.S             |   3 +
 arch/x86/kernel/i386_ksyms_32.c       |  44 --------
 arch/x86/kernel/mcount_64.S           |   2 +
 arch/x86/kernel/x8664_ksyms_64.c      |  79 ---------------
 arch/x86/lib/checksum_32.S            |   3 +
 arch/x86/lib/clear_page_64.S          |   2 +
 arch/x86/lib/cmpxchg8b_emu.S          |   2 +
 arch/x86/lib/copy_page_64.S           |   2 +
 arch/x86/lib/copy_user_64.S           |   8 ++
 arch/x86/lib/csum-partial_64.c        |   1 +
 arch/x86/lib/getuser.S                |   5 +
 arch/x86/lib/memcpy_64.S              |   3 +
 arch/x86/lib/memmove_64.S             |   3 +
 arch/x86/lib/memset_64.S              |   3 +
 arch/x86/lib/putuser.S                |   5 +
 arch/x86/lib/strstr_32.c              |   3 +-
 arch/x86/um/Makefile                  |   2 +-
 arch/x86/um/checksum_32.S             |   2 +
 arch/x86/um/ksyms.c                   |  13 ---
 include/asm-generic/export.h          |  66 ++++++++++++
 scripts/Makefile.build                |  20 ++++
 246 files changed, 769 insertions(+), 1215 deletions(-)
 delete mode 100644 arch/alpha/kernel/alpha_ksyms.c
 delete mode 100644 arch/arm/kernel/armksyms.c
 delete mode 100644 arch/arm/mach-imx/ssi-fiq-ksym.c
 create mode 100644 arch/ia64/include/asm/export.h
 create mode 100644 arch/m68k/include/asm/export.h
 delete mode 100644 arch/m68k/kernel/m68k_ksyms.c
 delete mode 100644 arch/powerpc/kernel/ppc_ksyms.c
 delete mode 100644 arch/powerpc/kernel/ppc_ksyms_32.c
 delete mode 100644 arch/powerpc/lib/ppc_ksyms.c
 delete mode 100644 arch/s390/kernel/s390_ksyms.c
 create mode 100644 arch/sparc/kernel/sparc_ksyms.c
 delete mode 100644 arch/sparc/kernel/sparc_ksyms_32.c
 delete mode 100644 arch/sparc/kernel/sparc_ksyms_64.c
 delete mode 100644 arch/sparc/lib/ksyms.c
 create mode 100644 arch/x86/include/asm/export.h
 delete mode 100644 arch/x86/kernel/i386_ksyms_32.c
 delete mode 100644 arch/x86/kernel/x8664_ksyms_64.c
 delete mode 100644 arch/x86/um/ksyms.c
 create mode 100644 include/asm-generic/export.h