One of the nice ideas behind paravirt is that CONFIG_XEN=y can be included
in a standard configuration and be no worse for native booting than as a
Xen guest. The glibc feature that supports the vDSO "nosegneg" note is
designed specifically to make this easy. You just have to flip one bit at
boot time. This patch makes Xen flip the bit, so a CONFIG_XEN=y kernel on
bare hardware does not make glibc use the less-optimized library builds.
Signed-off-by: Roland McGrath <roland@redhat.com>
Acked-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
arch/i386/xen/xen-asm.S defines some small pieces of code which are
used to implement a few paravirt_ops. They're designed so they can be
used either in-place, or be inline patched into their callsites if
there's enough space.
Some of those operations need to make calls out (specifically, if you
re-enable events [interrupts], and there's a pending event at that
time). These calls need the call instruction to be relocated if the
code is patched inline. In this case xen_foo_reloc is a
section-relative symbol which points to xen_foo's required relocation.
Other operations have no need of a relocation, and so their
corresponding xen_bar_reloc is absolute 0. These are the cases which
are triggering the warning.
This patch adds those symbols to the list of safe abs symbols.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Adrian Bunk <bunk@stusta.de>
Change the explicit code in the relocs.c file to use ARRAY_SIZE()
and add a definition of ARRAY_SIZE() since this is a userspace program
and wouldn't include kernel.h.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
i386 boot/compressed/relocs checks for absolute symbols and warns about
unexpected ones. If you build with modversions, you get ~2500 warnings
about __crc_<symbol>. These suckers are really absolute symbols - we
do _not_ want to modify them on relocation.
They are generated by genksyms - EXPORT_... generates a weak alias, then
genksyms produces an ld script with __crc_<symbol> = <checksum> and it's
fed to ld to produce the final object file. Their only use is to match
kernel and module at modprobe time; they _must_ be absolute.
boot/compressed/relocs has a whitelist of known absolute symbols, but
it doesn't know about __crc_... stuff. As the result, we get shitloads
of false positives on any ld(1) version.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
o Relocations generated w.r.t absolute symbols are not processed as by
definition, absolute symbols are not to be relocated. Explicitly warn
user about absolutions relocations present at compile time.
o These relocations get introduced either due to linker optimizations or
some programming oversights.
o Also create a list of symbols which have been audited to be safe and
don't emit warnings for these.
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
This patch modifies the i386 kernel so that if CONFIG_RELOCATABLE is
selected it will be able to be loaded at any 4K aligned address below
1G. The technique used is to compile the decompressor with -fPIC and
modify it so the decompressor is fully relocatable. For the main
kernel relocations are generated. Resulting in a kernel that is relocatable
with no runtime overhead and no need to modify the source code.
A reserved 32bit word in the parameters has been assigned
to serve as a stack so we figure out where are running.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
