32-bit:

 - Move definition of __init_begin outside output_section
   because it covers more than one section
 - Move ALIGN() for end-of-section inside .smp_locks output section.
   Same effect but the intent is better documented that
   we need both start and end aligned.

64-bit:

 - Move ALIGN() outside output section in .init.setup
 - Deleted unused __smp_alt_* symbols

None of the above should result in any functional change.

[ Impact: refactor and unify linker script ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-9-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[ Impact: cleanup ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-8-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

For 64 bit the following functional changes are introduced:

 - .data.page_aligned has moved
 - .data.cacheline_aligned has moved
 - .data.read_mostly has moved
 - ALIGN() moved out of output section for .data.cacheline_aligned
 - ALIGN() moved out of output section for .data.page_aligned

Notice that 32 bit and 64 bit has different location of _edata.
.data_nosave is 32 bit only as 64 bit is special due to PERCPU.

[ Impact: 32-bit: cleanup, 64-bit: use 32-bit linker script ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-7-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[ Impact: cleanup ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-6-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

32 bit x86 had a dedicated .text.head output section,
whereas 64 bit had it all in a single output section.

In the unified version the dedicated .text.head output section
was kept to have full control over the head code.

32 bit:

- Moved definition of _stext to the linker script.
  The definition is located _after_ .text.page_aligned as this
  is what 32 bit did before.

The ALIGN(8) was introduced so we hit the exact same address
(on the tested config) before and after the move.

I assume that it is a bug that _stext did not cover the
.text.page_aligned section - if this is true it can be fixed
in a follow-up patch (and the ugly ALIGN() can be dropped).

[ Impact: 64-bit: cleanup, 32-bit: use the 64-bit linker script ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-5-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[ Impact: cleanup ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-4-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

PHDRS are not equal for the two - so
use ifdefs to cover up for that.

On the assumption that they may become equal the ifdef
is inside the PHDRS definiton.

[ Impact: cleanup ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-3-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Merge everything except PHDRS and SECTIONS into
vmlinux.lds.S.

[ Impact: cleanup ]
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1240991249-27117-2-git-send-email-sam@ravnborg.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This changes the i386 linker script and the asm-generic macro it uses so that
ELF note sections with SHF_ALLOC set are linked into the kernel image along
with other read-only data.  The PT_NOTE also points to their location.

This paves the way for putting useful build-time information into ELF notes
that can be found easily later in a kernel memory dump.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

per cpu data section contains two types of data.  One set which is
exclusively accessed by the local cpu and the other set which is per cpu,
but also shared by remote cpus.  In the current kernel, these two sets are
not clearely separated out.  This can potentially cause the same data
cacheline shared between the two sets of data, which will result in
unnecessary bouncing of the cacheline between cpus.

One way to fix the problem is to cacheline align the remotely accessed per
cpu data, both at the beginning and at the end.  Because of the padding at
both ends, this will likely cause some memory wastage and also the
interface to achieve this is not clean.

This patch:

Moves the remotely accessed per cpu data (which is currently marked
as ____cacheline_aligned_in_smp) into a different section, where all the data
elements are cacheline aligned. And as such, this differentiates the local
only data and remotely accessed data cleanly.
Signed-off-by: NFenghua Yu <fenghua.yu@intel.com>
Acked-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: <linux-arch@vger.kernel.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch is a rollup of all the core pieces of the Xen
implementation, including:
 - booting and setup
 - pagetable setup
 - privileged instructions
 - segmentation
 - interrupt flags
 - upcalls
 - multicall batching

BOOTING AND SETUP

The vmlinux image is decorated with ELF notes which tell the Xen
domain builder what the kernel's requirements are; the domain builder
then constructs the address space accordingly and starts the kernel.

Xen has its own entrypoint for the kernel (contained in an ELF note).
The ELF notes are set up by xen-head.S, which is included into head.S.
In principle it could be linked separately, but it seems to provoke
lots of binutils bugs.

Because the domain builder starts the kernel in a fairly sane state
(32-bit protected mode, paging enabled, flat segments set up), there's
not a lot of setup needed before starting the kernel proper.  The main
steps are:
  1. Install the Xen paravirt_ops, which is simply a matter of a
     structure assignment.
  2. Set init_mm to use the Xen-supplied pagetables (analogous to the
     head.S generated pagetables in a native boot).
  3. Reserve address space for Xen, since it takes a chunk at the top
     of the address space for its own use.
  4. Call start_kernel()

PAGETABLE SETUP

Once we hit the main kernel boot sequence, it will end up calling back
via paravirt_ops to set up various pieces of Xen specific state.  One
of the critical things which requires a bit of extra care is the
construction of the initial init_mm pagetable.  Because Xen places
tight constraints on pagetables (an active pagetable must always be
valid, and must always be mapped read-only to the guest domain), we
need to be careful when constructing the new pagetable to keep these
constraints in mind.  It turns out that the easiest way to do this is
use the initial Xen-provided pagetable as a template, and then just
insert new mappings for memory where a mapping doesn't already exist.

This means that during pagetable setup, it uses a special version of
xen_set_pte which ignores any attempt to remap a read-only page as
read-write (since Xen will map its own initial pagetable as RO), but
lets other changes to the ptes happen, so that things like NX are set
properly.

PRIVILEGED INSTRUCTIONS AND SEGMENTATION

When the kernel runs under Xen, it runs in ring 1 rather than ring 0.
This means that it is more privileged than user-mode in ring 3, but it
still can't run privileged instructions directly.  Non-performance
critical instructions are dealt with by taking a privilege exception
and trapping into the hypervisor and emulating the instruction, but
more performance-critical instructions have their own specific
paravirt_ops.  In many cases we can avoid having to do any hypercalls
for these instructions, or the Xen implementation is quite different
from the normal native version.

The privileged instructions fall into the broad classes of:
  Segmentation: setting up the GDT and the GDT entries, LDT,
     TLS and so on.  Xen doesn't allow the GDT to be directly
     modified; all GDT updates are done via hypercalls where the new
     entries can be validated.  This is important because Xen uses
     segment limits to prevent the guest kernel from damaging the
     hypervisor itself.
  Traps and exceptions: Xen uses a special format for trap entrypoints,
     so when the kernel wants to set an IDT entry, it needs to be
     converted to the form Xen expects.  Xen sets int 0x80 up specially
     so that the trap goes straight from userspace into the guest kernel
     without going via the hypervisor.  sysenter isn't supported.
  Kernel stack: The esp0 entry is extracted from the tss and provided to
     Xen.
  TLB operations: the various TLB calls are mapped into corresponding
     Xen hypercalls.
  Control registers: all the control registers are privileged.  The most
     important is cr3, which points to the base of the current pagetable,
     and we handle it specially.

Another instruction we treat specially is CPUID, even though its not
privileged.  We want to control what CPU features are visible to the
rest of the kernel, and so CPUID ends up going into a paravirt_op.
Xen implements this mainly to disable the ACPI and APIC subsystems.

INTERRUPT FLAGS

Xen maintains its own separate flag for masking events, which is
contained within the per-cpu vcpu_info structure.  Because the guest
kernel runs in ring 1 and not 0, the IF flag in EFLAGS is completely
ignored (and must be, because even if a guest domain disables
interrupts for itself, it can't disable them overall).

(A note on terminology: "events" and interrupts are effectively
synonymous.  However, rather than using an "enable flag", Xen uses a
"mask flag", which blocks event delivery when it is non-zero.)

There are paravirt_ops for each of cli/sti/save_fl/restore_fl, which
are implemented to manage the Xen event mask state.  The only thing
worth noting is that when events are unmasked, we need to explicitly
see if there's a pending event and call into the hypervisor to make
sure it gets delivered.

UPCALLS

Xen needs a couple of upcall (or callback) functions to be implemented
by each guest.  One is the event upcalls, which is how events
(interrupts, effectively) are delivered to the guests.  The other is
the failsafe callback, which is used to report errors in either
reloading a segment register, or caused by iret.  These are
implemented in i386/kernel/entry.S so they can jump into the normal
iret_exc path when necessary.

MULTICALL BATCHING

Xen provides a multicall mechanism, which allows multiple hypercalls
to be issued at once in order to mitigate the cost of trapping into
the hypervisor.  This is particularly useful for context switches,
since the 4-5 hypercalls they would normally need (reload cr3, update
TLS, maybe update LDT) can be reduced to one.  This patch implements a
generic batching mechanism for hypercalls, which gets used in many
places in the Xen code.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Cc: Ian Pratt <ian.pratt@xensource.com>
Cc: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Cc: Adrian Bunk <bunk@stusta.de>

With this consolidation we can now modify the .data
section definition in one spot for all archs.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

Move definition of .text section to asm-generic.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

This reverts commit c9ccf30d.

Entering the kernel at startup_32 without passing our real mode data in
%esi, and without guaranteeing that physical and virtual addresses are
identity mapped makes head.S impossible to maintain.

The only user of this infrastructure is lguest which is not merged so
nothing we currently support will break by removing this over designed
nightmare, and only the pending lguest patches will be affected.  The
pending Xen patches have a different entry point that they use.

We are currently discussing what Xen and lguest need to do to boot the
kernel in a more normal fashion so using startup_32 in this weird manner is
clearly not their long term direction.

So let's remove this code in head.S before it causes brain damage to people
trying to maintain head.S

Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zachary Amsden <zach@vmware.com>
CC: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Three cleanups:

1: ELF notes are never mapped, so there's no need to have any access
flags in their phdr.

2: When generating them from asm, tell the assembler to use a SHT_NOTE
section type.  There doesn't seem to be a way to do this from C.

3: Use ANSI rather than traditional cpp behaviour to stringify the
macro argument.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Eric W. Biederman <ebiederm@xmission.com>

The other symbols used to delineate the alt-instructions sections have the
form __foo/__foo_end.  Rename parainstructions to match.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

Currently x86 (similar to x84-64) has a special per-cpu structure
called "i386_pda" which can be easily and efficiently referenced via
the %fs register.  An ELF section is more flexible than a structure,
allowing any piece of code to use this area.  Indeed, such a section
already exists: the per-cpu area.

So this patch:
(1) Removes the PDA and uses per-cpu variables for each current member.
(2) Replaces the __KERNEL_PDA segment with __KERNEL_PERCPU.
(3) Creates a per-cpu mirror of __per_cpu_offset called this_cpu_off, which
    can be used to calculate addresses for this CPU's variables.
(4) Simplifies startup, because %fs doesn't need to be loaded with a
    special segment at early boot; it can be deferred until the first
    percpu area is allocated (or never for UP).

The result is less code and one less x86-specific concept.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>

The .smp_altinstructions section and its corresponding symbols are
completely unused, so remove them.

Also, remove stray #ifdef __KENREL__ in asm-i386/alternative.h
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>

Let's allow page-alignment in general for per-cpu data (wanted by Xen, and
Ingo suggested KVM as well).

Because larger alignments can use more room, we increase the max per-cpu
memory to 64k rather than 32k: it's getting a little tight.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

On x86-64, kernel memory freed after init can be entirely unmapped instead
of just getting 'poisoned' by overwriting with a debug pattern.

On i386 and x86-64 (under CONFIG_DEBUG_RODATA), kernel text and bug table
can also be write-protected.

Compared to the first version, this one prevents re-creating deleted
mappings in the kernel image range on x86-64, if those got removed
previously. This, together with the original changes, prevents temporarily
having inconsistent mappings when cacheability attributes are being
changed on such pages (e.g. from AGP code). While on i386 such duplicate
mappings don't exist, the same change is done there, too, both for
consistency and because checking pte_present() before using various other
pte_XXX functions is a requirement anyway. At once, i386 code gets
adjusted to use pte_huge() instead of open coding this.

AK: split out cpa() changes
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NAndi Kleen <ak@suse.de>

Due to an over aggressive optimizer gcc 4.2 cannot optimize away _proxy_pda
in all cases (counter intuitive, but true).  This breaks loading of some
modules.

The earlier workaround to just export a dummy symbol didn't work unfortunately
because the module code ignores exports with 0 value.

Make it 1 instead.
Signed-off-by: NAndi Kleen <ak@suse.de>

o Entry startup_32 was in .text section but it was accessing some init
  data too and it prompts MODPOST to generate compilation warnings.

WARNING: vmlinux - Section mismatch: reference to .init.data:boot_params from
.text between '_text' (at offset 0xc0100029) and 'startup_32_smp'
WARNING: vmlinux - Section mismatch: reference to .init.data:boot_params from
.text between '_text' (at offset 0xc0100037) and 'startup_32_smp'
WARNING: vmlinux - Section mismatch: reference to
.init.data:init_pg_tables_end from .text between '_text' (at offset
0xc0100099) and 'startup_32_smp'

o Can't move startup_32 to .init.text as this entry point has to be at the
  start of bzImage. Hence moved startup_32 to a new section .text.head and
  instructed MODPOST to not to generate warnings if init data is being
  accessed from .text.head section. This code has been audited.

o SMP boot up code (startup_32_smp) can go into .init.text if CPU hotplug
  is not supported. Otherwise it generates more warnings

WARNING: vmlinux - Section mismatch: reference to .init.data:new_cpu_data from
.text between 'checkCPUtype' (at offset 0xc0100126) and 'is486'
WARNING: vmlinux - Section mismatch: reference to .init.data:new_cpu_data from
.text between 'checkCPUtype' (at offset 0xc0100130) and 'is486'
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NAndi Kleen <ak@suse.de>

Update all arch/*/kernel/vmlinux.lds.S to not include space for initramfs
when CONFIG_BLK_DEV_INITRAMFS is not selected.  This saves another 4 kbytes
on most platfoms (some reserve PAGE_SIZE for initramfs).
Signed-off-by: NJean-Paul Saman <jean-paul.saman@nxp.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The new PDA code uses a dummy _proxy_pda variable to describe
memory references to the PDA. It is never referenced
in inline assembly, but exists as input/output arguments.
gcc 4.2 in some cases can CSE references to this which causes
unresolved symbols.  Define it to zero to avoid this.
Signed-off-by: NAndi Kleen <ak@suse.de>

This makes i386 use the generic BUG machinery.  There are no functional
changes from the old i386 implementation.

The main advantage in using the generic BUG machinery for i386 is that the
inlined overhead of BUG is just the ud2a instruction; the file+line(+function)
information are no longer inlined into the instruction stream.  This reduces
cache pollution, and makes disassembly work properly.
Signed-off-by: NJeremy Fitzhardinge <jeremy@goop.org>
Cc: Andi Kleen <ak@muc.de>
Cc: Hugh Dickens <hugh@veritas.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The .eh_frame section contents is never written to, so it can as well
benefit from CONFIG_DEBUG_RODATA.

Diff-ed against firstfloor tree.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NAndi Kleen <ak@suse.de>

o Convert more absolute symbols to section relative to keep the theme in
  vmlinux.lds.S file and to avoid problem if kernel is relocated.

o Also put a message so that in future people can be aware of it and
  avoid introducing absolute symbols.
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>

1) Each hypervisor writes a probe function to detect whether we are
   running under that hypervisor.  paravirt_probe() registers this
   function.

2) If vmlinux is booted with ring != 0, we call all the probe
   functions (with registers except %esp intact) in link order: the
   winner will not return.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>

It turns out that the most called ops, by several orders of magnitude,
are the interrupt manipulation ops.  These are obvious candidates for
patching, so mark them up and create infrastructure for it.

The method used is that the ops structure has a patch function, which
is called for each place which needs to be patched: this returns a
number of instructions (the rest are NOP-padded).

Usually we can spare a register (%eax) for the binary patched code to
use, but in a couple of critical places in entry.S we can't: we make
the clobbers explicit at the call site, and manually clobber the
allowed registers in debug mode as an extra check.

And:

Don't abuse CONFIG_DEBUG_KERNEL, add CONFIG_DEBUG_PARAVIRT.

And:

AK:  Fix warnings in x86-64 alternative.c build

And:

AK: Fix compilation with defconfig

And:

^From: Andrew Morton <akpm@osdl.org>

Some binutlises still like to emit references to __stop_parainstructions and
__start_parainstructions.

And:

AK: Fix warnings about unused variables when PARAVIRT is disabled.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Signed-off-by: NZachary Amsden <zach@vmware.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>

o Now CONFIG_PHYSICAL_START is being replaced with CONFIG_PHYSICAL_ALIGN.
  Hardcoding the kernel physical start value creates a problem in relocatable
  kernel context due to boot loader limitations. For ex, if somebody
  compiles a relocatable kernel to be run from address 4MB, but this kernel
  will run from location 1MB as grub loads the kernel at physical address
  1MB. Kernel thinks that I am a relocatable kernel and I should run from
  the address I have been loaded at. So somebody wanting to run kernel
  from 4MB alignment location (for improved performance regions) can't do
  that.

o Hence, Eric proposed that probably CONFIG_PHYSICAL_ALIGN will make
  more sense in relocatable kernel context. At run time kernel will move
  itself to a physical addr location which meets user specified alignment
  restrictions.
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndi Kleen <ak@suse.de>

Defining __PHYSICAL_START and __KERNEL_START in asm-i386/page.h works but
it triggers a full kernel rebuild for the silliest of reasons.  This
modifies the users to directly use CONFIG_PHYSICAL_START and linux/config.h
which prevents the full rebuild problem, which makes the code much
more maintainer and hopefully user friendly.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndi Kleen <ak@suse.de>

Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndi Kleen <ak@suse.de>

Ld knows about 2 kinds of symbols,  absolute and section
relative.  Section relative symbols symbols change value
when a section is moved and absolute symbols do not.

Currently in the linker script we have several labels
marking the beginning and ending of sections that
are outside of sections, making them absolute symbols.
Having a mixture of absolute and section relative
symbols refereing to the same data is currently harmless
but it is confusing.

This must be done carefully as newer revs of ld do not place
symbols that appear in sections without data and instead
ld makes those symbols global :(

My ultimate goal is to build a relocatable kernel.  The
safest and least intrusive technique is to generate
relocation entries so the kernel can be relocated at load
time.  The only penalty would be an increase in the size
of the kernel binary.  The problem is that if absolute and
relocatable symbols are not properly specified absolute symbols
will be relocated or section relative symbols won't be, which
is fatal.

The practical motivation is that when generating kernels that
will run from a reserved area for analyzing what caused
a kernel panic, it is simpler if you don't need to hard code
the physical memory location they will run at, especially
for the distributions.

[AK: and merged:]

o Also put a message so that in future people can be aware of it and
  avoid introducing absolute symbols.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndi Kleen <ak@suse.de>

o Currently there is no specific alignment restriction in linker script
  and in some cases it can be placed non 4K aligned addresses. This fails
  kexec which checks that segment to be loaded is page aligned.

o I guess, it does not harm data segment to be 4K aligned.
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a vmlinux.lds.h helper macro for defining the eight-level initcall table,
teach all the architectures to use it.

This is a prerequisite for a patch which performs initcall synchronisation for
multithreaded-probing.

Cc: Greg KH <greg@kroah.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
[ Added AVR32 as well ]
Signed-off-by: NHaavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch will pack any .note.* section into a PT_NOTE segment in the output
file.

To do this, we tell ld that we need a PT_NOTE segment.  This requires us to
start explicitly mapping sections to segments, so we also need to explicitly
create PT_LOAD segments for text and data, and map the sections to them
appropriately.  Fortunately, each section will default to its previous
section's segment, so it doesn't take many changes to vmlinux.lds.S.

This only changes i386 for now, but I presume the corresponding changes for
other architectures will be as simple.

This change also adds <linux/elfnote.h>, which defines C and Assembler macros
for actually creating ELF notes.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

These are the i386-specific pieces to enable reliable stack traces. This is
going to be even more useful once CFI annotations get added to he assembly
code, namely to entry.S.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Considering that there isn't a lot of hw we can depend on during resume,
this is about as good as it gets.

This is x86-only for now, although the basic concept (and most of the
code) will certainly work on almost any platform.
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>