linux.git/arch/arm/kernel/head.S, branch v2.6.37 Linux kernel source tree ARM: 6504/1: Thumb-2: Fix long-distance conditional branches in head.S for Thumb-2. 2010-11-30T13:44:26+00:00 Dave Martin dave.martin@linaro.org 2010-11-29T18:43:28+00:00 a75e5248c51af1eaeed936be6bd3497b93f09685 The 32-bit conditional branches in Thumb-2 have a shorter range (+/-512K) than their ARM counterparts (+/-32MB). The linker does not currently generate trampolines to extend the range of these Thumb-2 conditional branches, resulting in link errors when vmlinux is sufficiently large, e.g.: head.o:(.text+0x464): relocation truncated to fit: R_ARM_THM_JUMP19 This patch forces the longer-range, unconditional branch encoding by use of an explicit IT instruction. The resulting branches are triggered on the same conditions as before. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 
The 32-bit conditional branches in Thumb-2 have a shorter range
(+/-512K) than their ARM counterparts (+/-32MB).  The linker does
not currently generate trampolines to extend the range of these
Thumb-2 conditional branches, resulting in link errors when vmlinux
is sufficiently large, e.g.:

head.o:(.text+0x464): relocation truncated to fit: R_ARM_THM_JUMP19

This patch forces the longer-range, unconditional branch encoding
by use of an explicit IT instruction.  The resulting branches are
triggered on the same conditions as before.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: 6500/1: Thumb-2: Correct data alignment for CONFIG_THUMB2_KERNEL in kernel/head.S 2010-11-30T13:44:24+00:00 Dave Martin dave.martin@linaro.org 2010-11-29T18:43:24+00:00 4f79a5dd7c3e316e2230dc0ee665c40a39023a81 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> 
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>
arm: use addruart macro to establish debug mappings 2010-10-20T04:27:34+00:00 Jeremy Kerr jeremy.kerr@canonical.com 2010-07-07T03:19:48+00:00 c293393faa8e11a5a80a9e358718432b8697f451 Since we can get both physical and virtual addresses from the addruart macro, we can use this to establish the debug mappings. In the case of CONFIG_DEBUG_ICEDCC, we don't need any mappings, but may still need to setup r7 correctly. Incorporating ASM changes from Nicolas Pitre <npitre@fluxnic.net>. Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com> Tested-by: Kevin Hilman <khilman@deeprootsystems.com> 
Since we can get both physical and virtual addresses from the addruart
macro, we can use this to establish the debug mappings.

In the case of CONFIG_DEBUG_ICEDCC, we don't need any mappings, but
may still need to setup r7 correctly.

Incorporating ASM changes from Nicolas Pitre <npitre@fluxnic.net>.

Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>
Merge branch 'hotplug' into devel 2010-10-18T21:34:47+00:00 Russell King rmk+kernel@arm.linux.org.uk 2010-10-18T21:34:47+00:00 a0a55682b83fd5f012afadcf415b030d7424ae68 Conflicts: arch/arm/kernel/head-common.S 
Conflicts:
	arch/arm/kernel/head-common.S
ARM: add register documentation for __enable_mmu 2010-10-08T09:07:35+00:00 Russell King rmk+kernel@arm.linux.org.uk 2010-10-04T17:02:59+00:00 865a4fae7793b80e2b8bca76e279d6dfecbeac17 Add some additional documentation on register usage in __enable_mmu to help complete the overall picture. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 
Add some additional documentation on register usage in __enable_mmu
to help complete the overall picture.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: hotplug cpu: move secondary_startup, __enable_mmu to cpuinit 2010-10-08T09:07:35+00:00 Russell King rmk+kernel@arm.linux.org.uk 2010-10-04T16:56:13+00:00 00945010c063b95e813b966f44bf58ffa1955a38 Move these two functions, both of which are required for secondary CPU booting, into the cpuinit section. Ensure bad processors call __error_p for better diagnostics, rather than just __error. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 
Move these two functions, both of which are required for secondary
CPU booting, into the cpuinit section.  Ensure bad processors call
__error_p for better diagnostics, rather than just __error.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: hotplug cpu: ensure that __enable_mmu is identity mapped 2010-10-08T09:07:34+00:00 Russell King rmk+kernel@arm.linux.org.uk 2010-10-04T16:51:54+00:00 786f1b73f7d5cad5c88dc75a96d53a74160aa7d7 __enable_mmu is required to be executed in an identity mapped region to ensure that variances in CPUs do not cause a crash. We currently achieve this by assuming that it will be co-located with __create_page_tables. With hotplug CPU support, this assumption becomes invalid. Implement a better solution which ensures that it will be appropriately mapped no matter where it is placed. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 
__enable_mmu is required to be executed in an identity mapped region
to ensure that variances in CPUs do not cause a crash.  We currently
achieve this by assuming that it will be co-located with
__create_page_tables.  With hotplug CPU support, this assumption
becomes invalid.  Implement a better solution which ensures that
it will be appropriately mapped no matter where it is placed.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: cleanup boot cpu calling __mmap_switched 2010-10-08T09:07:32+00:00 Russell King rmk+kernel@arm.linux.org.uk 2010-10-04T15:22:34+00:00 a4ae41341fd39af6e25ec9861a6a4dc0c5c58b16 This allows us to relocate __mmap_switched and associated data away from the head section. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 
This allows us to relocate __mmap_switched and associated data away
from the head section.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: Allow SMP kernels to boot on UP systems 2010-10-04T19:23:36+00:00 Russell King rmk+kernel@arm.linux.org.uk 2010-09-04T09:47:48+00:00 f00ec48fadf5e37e7889f14cff900aa70d18b644 UP systems do not implement all the instructions that SMP systems have, so in order to boot a SMP kernel on a UP system, we need to rewrite parts of the kernel. Do this using an 'alternatives' scheme, where the kernel code and data is modified prior to initialization to replace the SMP instructions, thereby rendering the problematical code ineffectual. We use the linker to generate a list of 32-bit word locations and their replacement values, and run through these replacements when we detect a UP system. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 
UP systems do not implement all the instructions that SMP systems have,
so in order to boot a SMP kernel on a UP system, we need to rewrite
parts of the kernel.

Do this using an 'alternatives' scheme, where the kernel code and data
is modified prior to initialization to replace the SMP instructions,
thereby rendering the problematical code ineffectual.  We use the linker
to generate a list of 32-bit word locations and their replacement values,
and run through these replacements when we detect a UP system.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ARM: convert to use __HEAD and HEAD_TEXT macros. 2009-11-23T20:33:34+00:00 Tim Abbott tabbott@ksplice.com 2009-10-02T20:32:46+00:00 2abc1c50b6be81233e0b79478dc04d8fec737ed5 This has the consequence of changing the section name used for head code from ".text.head" to ".head.text". Since this commit changes all users in the architecture, this change should be harmless. The .text.head output section is eliminated and the head text code is included at the start of the .init output section. Signed-off-by: Tim Abbott <tabbott@ksplice.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 
This has the consequence of changing the section name used for head
code from ".text.head" to ".head.text".  Since this commit changes all
users in the architecture, this change should be harmless.

The .text.head output section is eliminated and the head text code is
included at the start of the .init output section.

Signed-off-by: Tim Abbott <tabbott@ksplice.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>