arch/loongarch/kernel/lbt.S

Source file repositories/reference/linux-study-clean/arch/loongarch/kernel/lbt.S

File Facts

System: Linux kernel
Corpus path: arch/loongarch/kernel/lbt.S
Extension: .S
Size: 3189 bytes
Lines: 163
Domain: Architecture Layer
Bucket: arch/loongarch
Inferred role: Architecture Layer: exported/initcall integration point
Status: integration implementation candidate

Why This File Exists

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

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.
Exports symbols or registers init work; inspect boot/module ordering and who consumes the exported contract.

Dependency Surface

asm/asm.h
asm/asmmacro.h
asm/asm-extable.h
asm/asm-offsets.h
asm/errno.h
asm/regdef.h
asm/unwind_hints.h

Detected Declarations

export _save_lbt
export _restore_lbt
export _save_lbt_context
export _restore_lbt_context
export _save_ftop_context
export _restore_ftop_context

Annotated Snippet

#include <asm/asm.h>
#include <asm/asmmacro.h>
#include <asm/asm-extable.h>
#include <asm/asm-offsets.h>
#include <asm/errno.h>
#include <asm/regdef.h>
#include <asm/unwind_hints.h>

#define SCR_REG_WIDTH 8

	.macro	EX insn, reg, src, offs
.ex\@:	\insn	\reg, \src, \offs
	_asm_extable .ex\@, .L_lbt_fault
	.endm

/*
 * Save a thread's lbt context.
 */
SYM_FUNC_START(_save_lbt)
	movscr2gr	t1, $scr0		# save scr
	stptr.d		t1, a0, THREAD_SCR0
	movscr2gr	t1, $scr1
	stptr.d		t1, a0, THREAD_SCR1
	movscr2gr	t1, $scr2
	stptr.d		t1, a0, THREAD_SCR2
	movscr2gr	t1, $scr3
	stptr.d		t1, a0, THREAD_SCR3

	x86mfflag	t1, 0x3f		# save eflags
	stptr.d		t1, a0, THREAD_EFLAGS
	jr		ra
SYM_FUNC_END(_save_lbt)
EXPORT_SYMBOL(_save_lbt)

/*
 * Restore a thread's lbt context.
 */
SYM_FUNC_START(_restore_lbt)
	ldptr.d		t1, a0, THREAD_SCR0	# restore scr
	movgr2scr	$scr0, t1
	ldptr.d		t1, a0, THREAD_SCR1
	movgr2scr	$scr1, t1
	ldptr.d		t1, a0, THREAD_SCR2
	movgr2scr	$scr2, t1
	ldptr.d		t1, a0, THREAD_SCR3
	movgr2scr	$scr3, t1

	ldptr.d		t1, a0, THREAD_EFLAGS	# restore eflags
	x86mtflag	t1, 0x3f
	jr		ra
SYM_FUNC_END(_restore_lbt)
EXPORT_SYMBOL(_restore_lbt)

/*
 * Load scr/eflag with zero.
 */
SYM_FUNC_START(_init_lbt)
	movgr2scr	$scr0, zero
	movgr2scr	$scr1, zero
	movgr2scr	$scr2, zero
	movgr2scr	$scr3, zero

	x86mtflag	zero, 0x3f
	jr		ra
SYM_FUNC_END(_init_lbt)

/*
 * a0: scr
 * a1: eflag
 */

Annotation

Immediate include surface: `asm/asm.h`, `asm/asmmacro.h`, `asm/asm-extable.h`, `asm/asm-offsets.h`, `asm/errno.h`, `asm/regdef.h`, `asm/unwind_hints.h`.
Detected declarations: `export _save_lbt`, `export _restore_lbt`, `export _save_lbt_context`, `export _restore_lbt_context`, `export _save_ftop_context`, `export _restore_ftop_context`.
Atlas domain: Architecture Layer / arch/loongarch.
Implementation status: integration implementation candidate.

Implementation Notes

This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.