540b573875
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>
98 lines
2.3 KiB
ArmAsm
98 lines
2.3 KiB
ArmAsm
/*
|
|
* linux/arch/arm/kernel/head-nommu.S
|
|
*
|
|
* Copyright (C) 1994-2002 Russell King
|
|
* Copyright (C) 2003-2006 Hyok S. Choi
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*
|
|
* Common kernel startup code (non-paged MM)
|
|
*
|
|
*/
|
|
#include <linux/linkage.h>
|
|
#include <linux/init.h>
|
|
|
|
#include <asm/assembler.h>
|
|
#include <asm/ptrace.h>
|
|
#include <asm/asm-offsets.h>
|
|
#include <asm/thread_info.h>
|
|
#include <asm/system.h>
|
|
|
|
/*
|
|
* Kernel startup entry point.
|
|
* ---------------------------
|
|
*
|
|
* This is normally called from the decompressor code. The requirements
|
|
* are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
|
|
* r1 = machine nr.
|
|
*
|
|
* See linux/arch/arm/tools/mach-types for the complete list of machine
|
|
* numbers for r1.
|
|
*
|
|
*/
|
|
.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
|
|
#ifndef CONFIG_CPU_CP15
|
|
ldr r9, =CONFIG_PROCESSOR_ID
|
|
#else
|
|
mrc p15, 0, r9, c0, c0 @ get processor id
|
|
#endif
|
|
bl __lookup_processor_type @ r5=procinfo r9=cpuid
|
|
movs r10, r5 @ invalid processor (r5=0)?
|
|
beq __error_p @ yes, error 'p'
|
|
|
|
adr lr, BSYM(__after_proc_init) @ return (PIC) address
|
|
ARM( add pc, r10, #PROCINFO_INITFUNC )
|
|
THUMB( add r12, r10, #PROCINFO_INITFUNC )
|
|
THUMB( mov pc, r12 )
|
|
ENDPROC(stext)
|
|
|
|
/*
|
|
* Set the Control Register and Read the process ID.
|
|
*/
|
|
__after_proc_init:
|
|
#ifdef CONFIG_CPU_CP15
|
|
/*
|
|
* CP15 system control register value returned in r0 from
|
|
* the CPU init function.
|
|
*/
|
|
#ifdef CONFIG_ALIGNMENT_TRAP
|
|
orr r0, r0, #CR_A
|
|
#else
|
|
bic r0, r0, #CR_A
|
|
#endif
|
|
#ifdef CONFIG_CPU_DCACHE_DISABLE
|
|
bic r0, r0, #CR_C
|
|
#endif
|
|
#ifdef CONFIG_CPU_BPREDICT_DISABLE
|
|
bic r0, r0, #CR_Z
|
|
#endif
|
|
#ifdef CONFIG_CPU_ICACHE_DISABLE
|
|
bic r0, r0, #CR_I
|
|
#endif
|
|
#ifdef CONFIG_CPU_HIGH_VECTOR
|
|
orr r0, r0, #CR_V
|
|
#else
|
|
bic r0, r0, #CR_V
|
|
#endif
|
|
mcr p15, 0, r0, c1, c0, 0 @ write control reg
|
|
#endif /* CONFIG_CPU_CP15 */
|
|
|
|
b __mmap_switched @ clear the BSS and jump
|
|
@ to start_kernel
|
|
ENDPROC(__after_proc_init)
|
|
.ltorg
|
|
|
|
#include "head-common.S"
|