Andi Kleen [Thu, 7 Dec 2006 01:14:12 +0000 (02:14 +0100)]
[PATCH] unwinder: always use unlocked module list access in unwinder fallback
We're already well protected against module unloads because module
unload uses stop_machine(). The only exception is NMIs, but other
users already risk lockless accesses here.
This avoids some hackery in lockdep and also a potential deadlock
[PATCH] x86-64: Mark rdtsc as sync only for netburst, not for core2
On the Core2 cpus, the rdtsc instruction is not serializing (as defined
in the architecture reference since rdtsc exists) and due to the deep
speculation of these cores, it's possible that you can observe time go
backwards between cores due to this speculation. Since the kernel
already deals with this with the SYNC_RDTSC flag, the solution is
simple, only assume that the instruction is serializing on family 15...
The price one pays for this is a slightly slower gettimeofday (by a
dozen or two cycles), but that increase is quite small to pay for a
really-going-forward tsc counter.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andi Kleen <ak@suse.de>
Andi Kleen [Thu, 7 Dec 2006 01:14:12 +0000 (02:14 +0100)]
[PATCH] x86-64: Synchronize RDTSC on single core AMD
There is no guarantee that two RDTSCs in a row are monotonic,
so don't assume it on single core AMD systems.
This will make gettimeofday slower again Signed-off-by: Andi Kleen <ak@suse.de>
Karsten Wiese [Thu, 7 Dec 2006 01:14:11 +0000 (02:14 +0100)]
[PATCH] x86: Regard MSRs in lapic_suspend()/lapic_resume()
Read/Write APIC_LVTPC and APIC_LVTTHMR only,
if get_maxlvt() returns certain values.
This is done like everywhere else in i386/kernel/apic.c,
so I guess its correct.
Suspends/Resumes to disk fine and eleminates an smp_error_interrupt()
here on a K8.
Andi Kleen [Thu, 7 Dec 2006 01:14:11 +0000 (02:14 +0100)]
[PATCH] i386: Avoid boot warning with apic=debug
There are two consumers of apic=: the apic debug level and the low
level generic architecture code. early_param would warn when the
low level code rejected "debug". Avoid this.
[PATCH] i386: i386 add Intel BTS cpufeature bit and detection (take 2)
Here is a small patch for i386 which adds a cpufeature flag and
detection code for Intel's Branch Trace Store (BTS) feature. This
feature can be found on Intel P4 and Core 2 processors among others.
It can also be used by perfmon.
changelog:
- add CPU_FEATURE_BTS
- add Branch Trace Store detection
[PATCH] x86-64: x86-64 add Intel BTS cpufeature bit and detection (take 2)
Here is a small patch for x86-64 which adds a cpufeature flag and
detection code for Intel's Branch Trace Store (BTS) feature. This
feature can be found on Intel P4 and Core 2 processors among others.
It can also be used by perfmon.
changelog:
- add CPU_FEATURE_BTS
- add Branch Trace Store detection
[PATCH] x86: fix the irqbalance quirk for E7320/E7520/E7525
Move the irqbalance quirks for E7320/E7520/E7525(Errata 23 in
http://download.intel.com/design/chipsets/specupdt/30304203.pdf) to early
quirks.
And add a PCI quirk for these platforms to check(which happens very late
during the boot) if the APIC routing is indeed set to default flat mode.
This fixes the breakage(in x86_64) of this quirk due to cpu hotplug which
selects physical mode instead of the logical flat(as needed for this errata
workaround).
[PATCH] x86: add write_pci_config_byte() to direct PCI access routines
Mechanism of selecting physical mode in genapic when cpu hotplug is enabled on
x86_64, broke the quirk(quirk_intel_irqbalance()) introduced for working
around the transposing interrupt message errata in E7520/E7320/E7525 (revision
ID 0x9 and below. errata #23 in
http://download.intel.com/design/chipsets/specupdt/30304203.pdf).
This errata requires the mode to be in logical flat, so that interrupts can be
directed to more than one cpu(and thus use hardware IRQ balancing enabled by
BIOS on these platforms).
Following four patches fixes this by moving the quirk to early quirk and
forcing the x86_64 genapic selection to logical flat on these platforms.
Thanks to Shaohua for pointing out the breakage.
This patch:
Add write_pci_config_byte() to direct PCI access routines
Vivek Goyal [Thu, 7 Dec 2006 01:14:10 +0000 (02:14 +0100)]
[PATCH] relocatable kernel: Fix kallsyms on avr32 after relocatable kernel changes
o On some platforms like avr32, section init comes before .text and
not necessarily a symbol's relative position w.r.t _text is positive.
In such cases assembler detects the overflow and emits warning. This
patch fixes it.
Jan Beulich [Thu, 7 Dec 2006 01:14:09 +0000 (02:14 +0100)]
[PATCH] i386: fix MTRR code
Until not so long ago, there were system log messages pointing to
inconsistent MTRR setup of the video frame buffer caused by the way vesafb
and X worked. While vesafb was fixed meanwhile, I believe fixing it there
only hides a shortcoming in the MTRR code itself, in that that code is not
symmetric with respect to the ordering of attempts to set up two (or more)
regions where one contains the other. In the current shape, it permits
only setting up sub-regions of pre-exisiting ones. The patch below makes
this symmetric.
While working on that I noticed a few more inconsistencies in that code,
namely
- use of 'unsigned int' for sizes in many, but not all places (the patch
is converting this to use 'unsigned long' everywhere, which specifically
might be necessary for x86-64 once a processor supporting more than 44
physical address bits would become available)
- the code to correct inconsistent settings during secondary processor
startup tried (if necessary) to correct, among other things, the value
in IA32_MTRR_DEF_TYPE, however the newly computed value would never get
used (i.e. stored in the respective MSR)
- the generic range validation code checked that the end of the
to-be-added range would be above 1MB; the value checked should have been
the start of the range
- when contained regions are detected, previously this was allowed only
when the old region was uncacheable; this can be symmetric (i.e. the new
region can also be uncacheable) and even further as per Intel's
documentation write-trough and write-back for either region is also
compatible with the respective opposite in the other
Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andi Kleen <ak@suse.de>
Jan Beulich [Thu, 7 Dec 2006 01:14:09 +0000 (02:14 +0100)]
[PATCH] i386: clear_fixmap() should not use set_pte()
While not strictly required with the current code (as the upper half of
page table entries generated by __set_fixmap() cannot be non-zero due
to the second parameter of this function being 'unsigned long'), the
use of set_pte() in __set_fixmap() in the context of clear_fixmap() is
still improper with CONFIG_X86_PAE (see the respective comment in
include/asm-i386/pgtable-3level.h) and would turn into a bug if that
second parameter ever gets changed to a 64-bit type.
Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andi Kleen <ak@suse.de>
Ernie Petrides [Thu, 7 Dec 2006 01:14:09 +0000 (02:14 +0100)]
[PATCH] x86-64: fix perms/range of vsyscall vma in /proc/*/maps
The final line of /proc/<pid>/maps on x86_64 for native 64-bit
tasks shows an incorrect ending address and incorrect permissions. There
is only a single page mapped in this vsyscall region, and it is accessible
for both read and execute.
The patch below fixes this. (Since 32-bit-compat tasks have a real vma
with correct perms/range, no change is necessary for that scenario.)
Before the patch, a "cat /proc/self/maps | tail -1" shows this:
Andi Kleen [Thu, 7 Dec 2006 01:14:09 +0000 (02:14 +0100)]
[PATCH] x86-64: Add option to compile for Core2
Add an option to compile for Intel's Core 2
The Kconfig help is a mouthful due to the inventiveness of Intel's
product naming department.
Mainly for the 64bit cache line sizes because gcc doesn't support
optimizing for core2 yet. However it will and then the kernel
should be ready by passing the right option
Also fix the old MPSC help text to confirm better to reality.
Zachary Amsden [Thu, 7 Dec 2006 01:14:09 +0000 (02:14 +0100)]
[PATCH] paravirt: Add option to allow skipping the timer check
Add a way to disable the timer IRQ routing check via a boot option. The
VMI timer code uses this to avoid triggering the pester Mingo code, which
probes for some very unusual and broken motherboard routings. It fires
100% of the time when using a paravirtual delay mechanism instead of using
a realtime delay, since there is no elapsed real time, and the 4 timer IRQs
have not yet been delivered.
In addition, it is entirely possible, though improbable, that this bug
could surface on real hardware which picks a particularly bad time to enter
SMM mode, causing a long latency during one of the timer IRQs.
While here, make check_timer be __init.
Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andi Kleen <ak@suse.de>
[chrisw: use no_timer_check to bring inline with x86_64 as per Andi's request] Signed-off-by: Chris Wright <chrisw@sous-sol.org> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org>
Zachary Amsden [Thu, 7 Dec 2006 01:14:09 +0000 (02:14 +0100)]
[PATCH] paravirt: fix missing pte update
The function ptep_get_and_clear uses an atomic instruction sequence to get and
clear an active pte. Rather than add such an atomic operator to all virtual
machine implementations in paravirt-ops, it is easier to support the raw
atomic sequence and use either a trapping writable pagetable approach, or a
post-update notification. For the post update notification, we require the
pte_update function to be called after the access. Combine the 2-level and
3-level paging operators into one common function which does the post-update
notification, and rename the actual atomic sequences to raw_ptep_xxx
operators.
Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Andi Kleen <ak@muc.de> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@osdl.org>
Zachary Amsden [Thu, 7 Dec 2006 01:14:08 +0000 (02:14 +0100)]
[PATCH] paravirt: Preparatory mmu header movement
Move header includes for the nopud / nopmd types to the location of the actual
pte / pgd type definitions. This allows generic 4-level page type code to be
written before the split 2/3 level page table headers are included.
Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Andi Kleen <ak@muc.de> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@osdl.org>
Rusty Russell [Thu, 7 Dec 2006 01:14:08 +0000 (02:14 +0100)]
[PATCH] paravirt: Add MMU virtualization to paravirt_ops
Add the three bare TLB accessor functions to paravirt-ops. Most amusingly,
flush_tlb is redefined on SMP, so I can't call the paravirt op flush_tlb.
Instead, I chose to indicate the actual flush type, kernel (global) vs. user
(non-global). Global in this sense means using the global bit in the page
table entry, which makes TLB entries persistent across CR3 reloads, not
global as in the SMP sense of invoking remote shootdowns, so the term is
confusingly overloaded.
AK: folded in fix from Zach for PAE compilation
Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Andrew Morton <akpm@osdl.org>
Rusty Russell [Thu, 7 Dec 2006 01:14:08 +0000 (02:14 +0100)]
[PATCH] paravirt: Add APIC accessors to paravirt-ops.
Add APIC accessors to paravirt-ops. Unfortunately, we need two write
functions, as some older broken hardware requires workarounds for
Pentium APIC errata - this is the purpose of apic_write_atomic.
AK: replaced __inline with inline
Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Andrew Morton <akpm@osdl.org>
Rusty Russell [Thu, 7 Dec 2006 01:14:08 +0000 (02:14 +0100)]
[PATCH] paravirt: Allow disable power management under hypervisor
Two legacy power management modes are much easier to just explicitly disable
when running in paravirtualized mode - neither APM nor PnP is still relevant.
The status of ACPI is still debatable, and noacpi is still a common enough
boot parameter that it is not necessary to explicitly disable ACPI.
Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Andrew Morton <akpm@osdl.org>
Rusty Russell [Thu, 7 Dec 2006 01:14:08 +0000 (02:14 +0100)]
[PATCH] paravirt: Allow selected bug checks to be
Allow selected bug checks to be skipped by paravirt kernels. The two most
important are the F00F workaround (which is either done by the hypervisor,
or not required), and the 'hlt' instruction check, which can break under
some hypervisors.
Signed-off-by: Zachary Amsden <zach@vmware.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Andrew Morton <akpm@osdl.org>
Rusty Russell [Thu, 7 Dec 2006 01:14:08 +0000 (02:14 +0100)]
[PATCH] paravirt: Patch inline replacements for paravirt intercepts
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.
Rusty Russell [Thu, 7 Dec 2006 01:14:07 +0000 (02:14 +0100)]
[PATCH] paravirt: header and stubs for paravirtualisation
Create a paravirt.h header for all the critical operations which need to be
replaced with hypervisor calls, and include that instead of defining native
operations, when CONFIG_PARAVIRT.
This patch does the dumbest possible replacement of paravirtualized
instructions: calls through a "paravirt_ops" structure. Currently these are
function implementations of native hardware: hypervisors will override the ops
structure with their own variants.
All the pv-ops functions are declared "fastcall" so that a specific
register-based ABI is used, to make inlining assember easier.
And:
+From: Andy Whitcroft <apw@shadowen.org>
The paravirt ops introduce a 'weak' attribute onto memory_setup().
Code ordering leads to the following warnings on x86:
arch/i386/kernel/setup.c:651: warning: weak declaration of
`memory_setup' after first use results in unspecified behavior
Move memory_setup() to avoid this.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Zachary Amsden <zach@vmware.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Andy Whitcroft <apw@shadowen.org>
[PATCH] x86-64: Make x86_64 udelay() round up instead of down.
Port two patches from i386 to x86_64 delay.c to make sure all rounding is done
upward instead of downward.
There is no sign in commit messages that the mismatch was done on purpose, and
"delay() guarantees sleeping at least for the specified time" is still a valid
rule IMHO.
The original x86 patches are both from pre-GIT era, i.e.:
Muli Ben-Yehuda [Thu, 7 Dec 2006 01:14:06 +0000 (02:14 +0100)]
[PATCH] Calgary: check BBAR ioremap success when ioremapping
This patch cleans up the previous "Use BIOS supplied BBAR information"
patch. Mostly stylistic clenaups, but also check for ioremap failure
when we ioremap the BBAR rather than when trying to use it.
Laurent Vivier [Thu, 7 Dec 2006 01:14:06 +0000 (02:14 +0100)]
[PATCH] Calgary: use BIOS supplied BBARs and topology information
Find the BBAR register address of each Calgary using the "Extended
BIOS Data Area" rather than calculating it ourselves. Also get the bus
topology (what PHB each bus is on) from Calgary rather than
calculating it ourselves.
This patch fixes http://bugzilla.kernel.org/show_bug.cgi?id=7407.
bibo,mao [Thu, 7 Dec 2006 01:14:06 +0000 (02:14 +0100)]
[PATCH] i386: Move memory map printing and other code to e820.c
This patch moves e820 memory map print and memmap boot param
parsing function from setup.c to e820.c, also adds limit_regions
and print_memory_map declaration in header file.
bibo,mao [Thu, 7 Dec 2006 01:14:06 +0000 (02:14 +0100)]
[PATCH] i386: i386 create e820.c to handle standard io/mem resources
This patch creates new file named e820.c to hanle standard io/mem
resources, moving request_standard_resources function from setup.c
to e820.c. Also this patch modifies Makfile to compile file e820.c.
Albert Cahalan [Thu, 7 Dec 2006 01:14:06 +0000 (02:14 +0100)]
[PATCH] x86-64: Support -mregparm arguments for signals with SA_SIGINFO in compat mode
The recent change to make x86_64 support i386 binaries compiled
with -mregparm=3 only covered signal handlers without SA_SIGINFO.
(the 3-arg "real-time" ones)
To be compatible with i386, both types should be supported.
Signed-off-by: Albert Cahalan <acahalan@gmail.com> Signed-off-by: Andi Kleen <ak@suse.de>
Andi Kleen [Thu, 7 Dec 2006 01:14:06 +0000 (02:14 +0100)]
[PATCH] x86-64: Try multiple timer variants in check_timer
Instead of adding all kinds of more quirks try various timer
routing variants in check_timer.
In particular this tries to handle quirks from:
- Nvidia NF2-4 reference BIOS: wrong timer override
- Asus: Wrong timer override but no HPET table
- ATI: require timer disabled in 8259
- Some boards: require timer enabled in 8259
We just try many of the the known variants in the hopefully right order
in check_timer.
Andi Kleen [Thu, 7 Dec 2006 01:14:06 +0000 (02:14 +0100)]
[PATCH] i386: Use probe_kernel_address instead of __get_user in fault paths
Makes the intention of the code cleaner to read and avoids
a potential deadlock on mmap_sem. Also change the types of
the arguments to not include __user because they're really
not user addresses.
Yinghai Lu [Thu, 7 Dec 2006 01:14:05 +0000 (02:14 +0100)]
[PATCH] x86-64: Extend clear_irq_vector
Clear the irq releated entries in irq_vector, irq_domain and vector_irq
instead of clearing irq_vector only. So when new irq is created, it
could reuse that vector. (actually is the second loop scanning from
FIRST_DEVICE_VECTOR+8). This could avoid the vectors are used up
with enough module inserting and removing
Cc: Eric W. Biedierman <ebiederm@xmission.com> Cc: Muli Ben-Yehuda <muli@il.ibm.com> Signed-off-By: Yinghai Lu <yinghai.lu@amd.com> Signed-off-by: Andi Kleen <ak@suse.de>
Vivek Goyal [Thu, 7 Dec 2006 01:14:04 +0000 (02:14 +0100)]
[PATCH] i386: extend bzImage protocol for relocatable protected mode kernel
Extend bzImage protocol to enable bootloaders to load a completely relocatable
bzImage. Now protected mode component of kernel is also relocatable and a
boot-loader can load the protected mode component at a differnt physical
address than 1MB. (If kernel was built with CONFIG_RELOCATABLE)
Kexec can make use of it to load this kernel at a different physical address
to capture kernel crash dumps.
Vivek Goyal [Thu, 7 Dec 2006 01:14:04 +0000 (02:14 +0100)]
[PATCH] i386: Implement CONFIG_PHYSICAL_ALIGN
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.
Vivek Goyal [Thu, 7 Dec 2006 01:14:04 +0000 (02:14 +0100)]
[PATCH] i386: Warn upon absolute relocations being present
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.
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>
Print the addresses of non-absolute symbols relative to _text
so that ld will generate relocations. Allowing a relocatable
kernel to relocate them. We can't actually use the symbol names
because kallsyms includes static symbols that are not exported
from their object files.
Add the _text symbol definitions to the architectures which don't
define it otherwise linker will fail.
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>
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: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com> Signed-off-by: Andi Kleen <ak@suse.de>
[PATCH] i386: Reserve kernel memory starting from _text
Currently when we are reserving the memory the kernel text
resides in we start at __PHYSICAL_START which happens to be
correct but not very obvious. In addition when we start relocating
the kernel __PHYSICAL_START is the wrong value, as it is an
absolute symbol that does not get relocated.
By starting the reservation at __pa_symbol(_text)
the code is clearer and will be correct when relocated.
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>
On x86_64 we have to be careful with calculating the physical
address of kernel symbols. Both because of compiler odditities
and because the symbols live in a different range of the virtual
address space.
Having a defintition of __pa_symbol that works on both x86_64 and
i386 simplifies writing code that works for both x86_64 and
i386 that has these kinds of dependencies.
So this patch adds the trivial i386 __pa_symbol definition.
Added assembly magic similar to RELOC_HIDE as suggested by Andi Kleen.
Just picked it up from x86_64.
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>
Vivek Goyal [Thu, 7 Dec 2006 01:14:03 +0000 (02:14 +0100)]
[PATCH] i386: Distinguish absolute symbols
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: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com> Signed-off-by: Andi Kleen <ak@suse.de>
projects / linux-beck.git / log