arch/loongarch/kernel/mcount.S

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

File Facts

System
Linux kernel
Corpus path
arch/loongarch/kernel/mcount.S
Extension
.S
Size
2329 bytes
Lines
102
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.

Dependency Surface

Detected Declarations

Annotated Snippet

#include <linux/export.h>
#include <asm/ftrace.h>
#include <asm/regdef.h>
#include <asm/stackframe.h>

	.text

#define MCOUNT_S0_OFFSET	(0)
#define MCOUNT_RA_OFFSET	(SZREG)
#define MCOUNT_STACK_SIZE	(2 * SZREG)

	.macro MCOUNT_SAVE_REGS
	PTR_ADDI	sp, sp, -MCOUNT_STACK_SIZE
	PTR_S		s0, sp, MCOUNT_S0_OFFSET
	PTR_S		ra, sp, MCOUNT_RA_OFFSET
	move		s0, a0
	.endm

	.macro MCOUNT_RESTORE_REGS
	move		a0, s0
	PTR_L		ra, sp, MCOUNT_RA_OFFSET
	PTR_L		s0, sp, MCOUNT_S0_OFFSET
	PTR_ADDI	sp, sp, MCOUNT_STACK_SIZE
	.endm

SYM_FUNC_START(_mcount)
	la.pcrel	t1, ftrace_stub
	la.pcrel	t2, ftrace_trace_function	/* Prepare t2 for (1) */
	PTR_L		t2, t2, 0
	beq		t1, t2, fgraph_trace

	MCOUNT_SAVE_REGS

	move		a0, ra				/* arg0: self return address */
	move		a1, s0				/* arg1: parent's return address */
	jirl		ra, t2, 0			/* (1) call *ftrace_trace_function */

	MCOUNT_RESTORE_REGS

fgraph_trace:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	la.pcrel	t1, ftrace_stub
	la.pcrel	t3, ftrace_graph_return
	PTR_L		t3, t3, 0
	bne		t1, t3, ftrace_graph_caller
	la.pcrel	t1, ftrace_graph_entry_stub
	la.pcrel	t3, ftrace_graph_entry
	PTR_L		t3, t3, 0
	bne		t1, t3, ftrace_graph_caller
#endif

SYM_INNER_LABEL(ftrace_stub, SYM_L_GLOBAL)
	jr		ra
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
SYM_INNER_LABEL(ftrace_graph_func, SYM_L_GLOBAL)
	bl		ftrace_stub
#endif
SYM_FUNC_END(_mcount)
EXPORT_SYMBOL(_mcount)

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
SYM_FUNC_START(ftrace_graph_caller)
	MCOUNT_SAVE_REGS

	PTR_ADDI	a0, ra, -4			/* arg0: Callsite self return addr */
	PTR_ADDI	a1, sp, MCOUNT_STACK_SIZE	/* arg1: Callsite sp */
	move		a2, s0				/* arg2: Callsite parent ra */
	bl		prepare_ftrace_return

	MCOUNT_RESTORE_REGS

Annotation

Implementation Notes