arch/arm/kernel/head-common.S

Source file repositories/reference/linux-study-clean/arch/arm/kernel/head-common.S

File Facts

System
Linux kernel
Corpus path
arch/arm/kernel/head-common.S
Extension
.S
Size
5606 bytes
Lines
240
Domain
Architecture Layer
Bucket
arch/arm
Inferred role
Architecture Layer: arch/arm
Status
atlas-only

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

b	start_kernel
ENDPROC(__mmap_switched)

	.align	2
	.type	__mmap_switched_data, %object
__mmap_switched_data:
#ifdef CONFIG_XIP_KERNEL
#ifndef CONFIG_XIP_DEFLATED_DATA
	.long	_sdata				@ r0
	.long	__data_loc			@ r1
	.long	_edata_loc			@ r2
#endif
	.long	__bss_stop			@ sp (temporary stack in .bss)
#endif

	.long	__bss_start			@ r0
	.long	__bss_stop			@ r1
	.long	init_thread_union + THREAD_START_SP @ sp

	.long	processor_id			@ r0
	.long	__machine_arch_type		@ r1
	.long	__atags_pointer			@ r2
#ifdef CONFIG_CPU_CP15
	.long	cr_alignment			@ r3
#else
M_CLASS(.long	exc_ret)			@ r3
AR_CLASS(.long	0)				@ r3
#endif
	.size	__mmap_switched_data, . - __mmap_switched_data

	__FINIT
	.text

/*
 * This provides a C-API version of __lookup_processor_type
 */
ENTRY(lookup_processor_type)
	stmfd	sp!, {r4 - r6, r9, lr}
	mov	r9, r0
	bl	__lookup_processor_type
	mov	r0, r5
	ldmfd	sp!, {r4 - r6, r9, pc}
ENDPROC(lookup_processor_type)

/*
 * Read processor ID register (CP#15, CR0), and look up in the linker-built
 * supported processor list.  Note that we can't use the absolute addresses
 * for the __proc_info lists since we aren't running with the MMU on
 * (and therefore, we are not in the correct address space).  We have to
 * calculate the offset.
 *
 *	r9 = cpuid
 * Returns:
 *	r3, r4, r6 corrupted
 *	r5 = proc_info pointer in physical address space
 *	r9 = cpuid (preserved)
 */
__lookup_processor_type:
	/*
	 * Look in <asm/procinfo.h> for information about the __proc_info
	 * structure.
	 */
	adr_l	r5, __proc_info_begin
	adr_l	r6, __proc_info_end
1:	ldmia	r5, {r3, r4}			@ value, mask
	and	r4, r4, r9			@ mask wanted bits
	teq	r3, r4
	beq	2f
	add	r5, r5, #PROC_INFO_SZ		@ sizeof(proc_info_list)
	cmp	r5, r6

Annotation

Implementation Notes