ARMv6 and greater introduced a new instruction ("bx") which can be used
to return from function calls. Recent CPUs perform better when the
"bx lr" instruction is used rather than the "mov pc, lr" instruction,
and this sequence is strongly recommended to be used by the ARM
architecture manual (section A.4.1.1).
We provide a new macro "ret" with all its variants for the condition
code which will resolve to the appropriate instruction.
Rather than doing this piecemeal, and miss some instances, change all
the "mov pc" instances to use the new macro, with the exception of
the "movs" instruction and the kprobes code. This allows us to detect
the "mov pc, lr" case and fix it up - and also gives us the possibility
of deploying this for other registers depending on the CPU selection.
Reported-by: Will Deacon <will.deacon@arm.com>
Tested-by: Stephen Warren <swarren@nvidia.com> # Tegra Jetson TK1
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> # mioa701_bootresume.S
Tested-by: Andrew Lunn <andrew@lunn.ch> # Kirkwood
Tested-by: Shawn Guo <shawn.guo@freescale.com>
Tested-by: Tony Lindgren <tony@atomide.com> # OMAPs
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com> # Armada XP, 375, 385
Acked-by: Sekhar Nori <nsekhar@ti.com> # DaVinci
Acked-by: Christoffer Dall <christoffer.dall@linaro.org> # kvm/hyp
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com> # PXA3xx
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> # Xen
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> # ARMv7M
Tested-by: Simon Horman <horms+renesas@verge.net.au> # Shmobile
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Copying a function with memcpy() and then trying to execute the
result isn't trivially portable to Thumb.
This patch modifies the kexec soft restart code to copy its
assembler trampoline relocate_new_kernel() using fncpy() instead,
so that relocate_new_kernel can be in the same ISA as the rest of
the kernel without problems.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Reported-by: Taras Kondratiuk <taras.kondratiuk@linaro.org>
Tested-by: Taras Kondratiuk <taras.kondratiuk@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Commit 540b5738 ("ARM: 6999/1: head, zImage: Always Enter the kernel in
ARM state") mandates that the kernel should be entered in ARM state.
If a Thumb-2 kernel kexecs a new kernel image, we need to ensure that
we change state when branching to the new code. This patch replaces a
mov pc, lr with a bx lr on Thumb-2 kernels so that we transition to ARM
state if need be.
Reviewed-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Directives such as .long and .word do not magically cause the
assembler location counter to become aligned in gas. As a result,
using these directives in code sections can result in misaligned
data words when building a Thumb-2 kernel (CONFIG_THUMB2_KERNEL).
This is a Bad Thing, since the ABI permits the compiler to assume
that fundamental types of word size or above are word- aligned when
accessing them from C. If the data is not really word-aligned,
this can cause impaired performance and stray alignment faults in
some circumstances.
In general, the following rules should be applied when using data
word declaration directives inside code sections:
* .quad and .double:
.align 3
* .long, .word, .single, .float:
.align (or .align 2)
* .short:
No explicit alignment required, since Thumb-2
instructions are always 2 or 4 bytes in size.
immediately after an instruction.
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
When we are crashing there is no indirection page in place. Only
control page is present.
Signed-off-by: Mika Westerberg <ext-mika.1.westerberg@nokia.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Currently, the atags used by kexec are fixed to the ones originally used
to boot the kernel. This is less than ideal as changing the commandline,
initrd and other options would be a useful feature.
This patch exports the atags used for the current kernel to userspace
through an "atags" file in procfs. The presence of the file is
controlled by its own Kconfig option and cleans up several ifdef blocks
into a separate file. The tags for the new kernel are assumed to be at
a fixed location before the kernel image itself. The location of the
tags used to boot the original kernel is unimportant and no longer
saved.
Based on a patch from Uli Luckas <u.luckas@road.de>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Acked-by: Uli Luckas <u.luckas@road.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This patch resolves a kexec boot failure that can occur because
no ATAGs are passed in to the kexec'd kernel. Currently the
newly-kexec'd kernel may fail if it requires specific ATAGs, or
it may fail because the fixed memory location at which it expects
to find the ATAGs may contain random data instead of ATAGs.
The patch ensures that any ATAGs passed to the current kernel
at boot time are copied to a static buffer, and are copied back
when kexec copies the new kernel into place. Thus the new
kernel sees the same ATAGs from kexec and the boot loader.
The boot parameters are copied without regard to type, content,
or length -- this patch's scope is limited soley to saving and
restoring a fixed-size block of memory containing the kernel's
boot parameters. Additional functionality to examine, alter, or
replace the ATAGs (using kexec, for example) can be implemented
by manipulating the static buffer containing the preserved ATAGs.
Note: the size of the buffer (1.5KB) is selected to comfortably
hold one of each ATAG type, including a maximum-length command
line and the maximum number of ATAG_MEM structures currently
supported by the kernel. Should an ATAG list exceed that limit,
the list will be silently truncated to that limit (to do other-
wise at that point in the boot process would make a simple
problem exceedingly complicated).
[Note: this is the same patch as 4579, modified to accomodate
the ATAG changes introduced in 2.6.23]
Signed-off-by: Mike Westerhof <mwester at dls.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Add kexec support to ARM.
Improvements like commandline handling could be made but this patch gives
basic functional support. It uses the next available syscall number, 347.
Once the syscall number is known, userspace support will be
finalised/submitted to kexec-tools, various patches already exist.
Originally based on a patch by Maxim Syrchin but updated and forward
ported by various people.
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Russell King