linux/arch
Andy Lutomirski 6f121e548f x86, vdso: Reimplement vdso.so preparation in build-time C
Currently, vdso.so files are prepared and analyzed by a combination
of objcopy, nm, some linker script tricks, and some simple ELF
parsers in the kernel.  Replace all of that with plain C code that
runs at build time.

All five vdso images now generate .c files that are compiled and
linked in to the kernel image.

This should cause only one userspace-visible change: the loaded vDSO
images are stripped more heavily than they used to be.  Everything
outside the loadable segment is dropped.  In particular, this causes
the section table and section name strings to be missing.  This
should be fine: real dynamic loaders don't load or inspect these
tables anyway.  The result is roughly equivalent to eu-strip's
--strip-sections option.

The purpose of this change is to enable the vvar and hpet mappings
to be moved to the page following the vDSO load segment.  Currently,
it is possible for the section table to extend into the page after
the load segment, so, if we map it, it risks overlapping the vvar or
hpet page.  This happens whenever the load segment is just under a
multiple of PAGE_SIZE.

The only real subtlety here is that the old code had a C file with
inline assembler that did 'call VDSO32_vsyscall' and a linker script
that defined 'VDSO32_vsyscall = __kernel_vsyscall'.  This most
likely worked by accident: the linker script entry defines a symbol
associated with an address as opposed to an alias for the real
dynamic symbol __kernel_vsyscall.  That caused ld to relocate the
reference at link time instead of leaving an interposable dynamic
relocation.  Since the VDSO32_vsyscall hack is no longer needed, I
now use 'call __kernel_vsyscall', and I added -Bsymbolic to make it
work.  vdso2c will generate an error and abort the build if the
resulting image contains any dynamic relocations, so we won't
silently generate bad vdso images.

(Dynamic relocations are a problem because nothing will even attempt
to relocate the vdso.)

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/2c4fcf45524162a34d87fdda1eb046b2a5cecee7.1399317206.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2014-05-05 13:18:51 -07:00
..
alpha Merge git://git.infradead.org/users/eparis/audit 2014-04-12 12:38:53 -07:00
arc ARC: !PREEMPT: Ensure Return to kernel mode is IRQ safe 2014-04-30 08:21:43 -07:00
arm - Fix for a Haswell regression in nested virtualization, introduced during 2014-05-02 09:26:09 -07:00
arm64 arm64: Mark the Applied Micro X-Gene SATA controller as DMA coherent 2014-05-03 22:20:35 +01:00
avr32 Char/Misc driver patches for 3.15-rc1 2014-04-01 16:13:21 -07:00
blackfin blackfin updates for Linux 3.15 2014-04-12 17:26:45 -07:00
c6x Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-03-31 10:59:39 -07:00
cris Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
frv PCI changes for the v3.15 merge window: 2014-04-01 15:14:04 -07:00
hexagon Hexagon: Delete stale barrier.h 2014-05-01 10:09:47 -07:00
ia64 mm: split 'tlb_flush_mmu()' into tlb flushing and memory freeing parts 2014-04-25 16:05:40 -07:00
m32r Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
m68k Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
metag Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
microblaze Microblaze patches for 3.15-rc1 2014-04-11 11:53:45 -07:00
mips Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-04-27 11:21:03 -07:00
mn10300 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-04-12 14:49:50 -07:00
openrisc Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
parisc Merge branch 'parisc-3.15-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2014-05-01 15:54:44 -07:00
powerpc powerpc/4xx: Fix section mismatch in ppc4xx_pci.c 2014-04-28 16:32:53 +10:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2014-05-02 09:25:32 -07:00
score score: remove unused CPU_SCORE7 Kconfig parameter 2014-04-03 16:20:52 -07:00
sh mm: split 'tlb_flush_mmu()' into tlb flushing and memory freeing parts 2014-04-25 16:05:40 -07:00
sparc Merge git://git.infradead.org/users/eparis/audit 2014-04-12 12:38:53 -07:00
tile Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
um mm: split 'tlb_flush_mmu()' into tlb flushing and memory freeing parts 2014-04-25 16:05:40 -07:00
unicore32 Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
x86 x86, vdso: Reimplement vdso.so preparation in build-time C 2014-05-05 13:18:51 -07:00
xtensa Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-04-12 14:49:50 -07:00
.gitignore
Kconfig uprobes: Kconfig dependency fix 2014-03-18 16:39:33 -04:00