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| author | Dave Martin <dave.martin@linaro.org> | 2011-07-13 15:53:30 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2011-07-19 12:00:53 +0100 |
| commit | 540b573875bd26dfe39aa18d22dc195f275fc0df (patch) | |
| tree | d4fc0c012ef109d601e28814b3806eb44ce357c7 /arch/arm/kernel/head.S | |
| parent | c7e89b16eb90e7bdf0d71bd5ba265ce8d424f30b (diff) | |
| download | blackbird-op-linux-540b573875bd26dfe39aa18d22dc195f275fc0df.tar.gz blackbird-op-linux-540b573875bd26dfe39aa18d22dc195f275fc0df.zip | |
ARM: 6999/1: head, zImage: Always Enter the kernel in ARM state
Currently, the documented kernel entry requirements are not
explicit about whether the kernel should be entered in ARM or
Thumb, leading to an ambiguitity about how to enter Thumb-2
kernels. As a result, the kernel is reliant on the zImage
decompressor to enter the kernel proper in the correct instruction
set state.
This patch changes the boot entry protocol for head.S and Image to
be the same as for zImage: in all cases, the kernel is now entered
in ARM.
Documentation/arm/Booting is updated to reflect this new policy.
A different rule will be needed for Cortex-M class CPUs as and when
support for those lands in mainline, since these CPUs don't support
the ARM instruction set at all: a note is added to the effect that
the kernel must be entered in Thumb on such systems.
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/head.S')
| -rw-r--r-- | arch/arm/kernel/head.S | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S index 278c1b0ebb2e..742b6108a001 100644 --- a/arch/arm/kernel/head.S +++ b/arch/arm/kernel/head.S @@ -71,8 +71,16 @@ * crap here - that's what the boot loader (or in extreme, well justified * circumstances, zImage) is for. */ + .arm + __HEAD ENTRY(stext) + + THUMB( adr r9, BSYM(1f) ) @ Kernel is always entered in ARM. + THUMB( bx r9 ) @ If this is a Thumb-2 kernel, + THUMB( .thumb ) @ switch to Thumb now. + THUMB(1: ) + setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode @ and irqs disabled mrc p15, 0, r9, c0, c0 @ get processor id |
