Commit dbe3ba30 authored by Qing Zhang's avatar Qing Zhang Committed by Huacai Chen
Browse files

LoongArch/ftrace: Add basic support 



This patch contains basic ftrace support for LoongArch. Specifically,
function tracer (HAVE_FUNCTION_TRACER), function graph tracer (HAVE_
FUNCTION_GRAPH_TRACER) are implemented following the instructions in
Documentation/trace/ftrace-design.txt.

Use `-pg` makes stub like a child function `void _mcount(void *ra)`.
Thus, it can be seen store RA and alloc stack before `call _mcount`.
Find `alloc stack` at first, and then find `store RA`.

Note that the functions in both inst.c and time.c should not be hooked
with the compiler's -pg option: to prevent infinite self-referencing for
the former, and to ignore early setup stuff for the latter.

Co-developed-by: default avatarJinyang He <hejinyang@loongson.cn>
Signed-off-by: default avatarJinyang He <hejinyang@loongson.cn>
Signed-off-by: default avatarQing Zhang <zhangqing@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 9151dde4

arch/loongarch/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -90,6 +90,8 @@ config LOONGARCH 
	select HAVE_EBPF_JIT

	select HAVE_EXIT_THREAD

	select HAVE_FAST_GUP

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_FUNCTION_TRACER

	select HAVE_GENERIC_VDSO

	select HAVE_IOREMAP_PROT

	select HAVE_IRQ_EXIT_ON_IRQ_STACK

arch/loongarch/include/asm/ftrace.h

0 → 100644
+21 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

/*

 * Copyright (C) 2022 Loongson Technology Corporation Limited

 */



#ifndef _ASM_LOONGARCH_FTRACE_H

#define _ASM_LOONGARCH_FTRACE_H



#ifdef CONFIG_FUNCTION_TRACER



#define MCOUNT_INSN_SIZE 4		/* sizeof mcount call */



#ifndef __ASSEMBLY__

#define mcount _mcount

extern void _mcount(void);

extern void prepare_ftrace_return(unsigned long self_addr, unsigned long callsite_sp, unsigned long old);

#endif /* __ASSEMBLY__ */



#endif /* CONFIG_FUNCTION_TRACER */



#endif /* _ASM_LOONGARCH_FTRACE_H */

arch/loongarch/kernel/Makefile

+8 −0
Original line number Diff line number Diff line
@@ -15,6 +15,14 @@ obj-$(CONFIG_EFI) += efi.o 


obj-$(CONFIG_CPU_HAS_FPU)	+= fpu.o



ifdef CONFIG_FUNCTION_TRACER

obj-y += mcount.o ftrace.o

CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)

CFLAGS_REMOVE_inst.o = $(CC_FLAGS_FTRACE)

CFLAGS_REMOVE_time.o = $(CC_FLAGS_FTRACE)

CFLAGS_REMOVE_perf_event.o = $(CC_FLAGS_FTRACE)

endif



obj-$(CONFIG_MODULES)		+= module.o module-sections.o

obj-$(CONFIG_STACKTRACE)	+= stacktrace.o

arch/loongarch/kernel/ftrace.c

0 → 100644
+73 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Copyright (C) 2022 Loongson Technology Corporation Limited

 */



#include <linux/init.h>

#include <linux/ftrace.h>

#include <linux/syscalls.h>

#include <linux/uaccess.h>



#include <asm/asm.h>

#include <asm/asm-offsets.h>

#include <asm/cacheflush.h>

#include <asm/inst.h>

#include <asm/loongarch.h>

#include <asm/syscall.h>



#include <asm-generic/sections.h>



#ifdef CONFIG_FUNCTION_GRAPH_TRACER



/*

 * As `call _mcount` follows LoongArch psABI, ra-saved operation and

 * stack operation can be found before this insn.

 */



static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off)

{

	int limit = 32;

	union loongarch_instruction *insn;



	insn = (union loongarch_instruction *)insn_addr;



	do {

		insn--;

		limit--;



		if (is_ra_save_ins(insn))

			*ra_off = -((1 << 12) - insn->reg2i12_format.immediate);



	} while (!is_stack_alloc_ins(insn) && limit);



	if (!limit)

		return -EINVAL;



	return 0;

}



void prepare_ftrace_return(unsigned long self_addr,

		unsigned long callsite_sp, unsigned long old)

{

	int ra_off;

	unsigned long return_hooker = (unsigned long)&return_to_handler;



	if (unlikely(ftrace_graph_is_dead()))

		return;



	if (unlikely(atomic_read(&current->tracing_graph_pause)))

		return;



	if (ftrace_get_parent_ra_addr(self_addr, &ra_off))

		goto out;



	if (!function_graph_enter(old, self_addr, 0, NULL))

		*(unsigned long *)(callsite_sp + ra_off) = return_hooker;



	return;



out:

	ftrace_graph_stop();

	WARN_ON(1);

}

#endif	/* CONFIG_FUNCTION_GRAPH_TRACER */

arch/loongarch/kernel/mcount.S

0 → 100644
+96 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

/*

 * LoongArch specific _mcount support

 *

 * Copyright (C) 2022 Loongson Technology Corporation Limited

 */



#include <asm/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

	jr		ra

SYM_FUNC_END(ftrace_graph_caller)



SYM_FUNC_START(return_to_handler)

	PTR_ADDI	sp, sp, -2 * SZREG

	PTR_S		a0, sp, 0

	PTR_S		a1, sp, SZREG



	bl		ftrace_return_to_handler



	/* Restore the real parent address: a0 -> ra */

	move		ra, a0



	PTR_L		a0, sp, 0

	PTR_L		a1, sp, SZREG

	PTR_ADDI	sp, sp, 2 * SZREG

	jr		ra

SYM_FUNC_END(return_to_handler)

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */