Commit 5fcfad3d authored by Qing Zhang's avatar Qing Zhang Committed by Huacai Chen
Browse files

LoongArch/ftrace: Add dynamic function graph tracer support 



Once the function_graph tracer is enabled, a filtered function has the
following call sequence:

1) ftracer_caller     ==> on/off by ftrace_make_call/ftrace_make_nop
2) ftrace_graph_caller
3) ftrace_graph_call  ==> on/off by ftrace_en/disable_ftrace_graph_caller
4) prepare_ftrace_return

Considering the following DYNAMIC_FTRACE_WITH_REGS feature, it would be
more extendable to have a ftrace_graph_caller function, instead of
calling prepare_ftrace_return directly in ftrace_caller.

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 4733f09d

arch/loongarch/kernel/ftrace_dyn.c

+44 −0
Original line number Diff line number Diff line
@@ -108,3 +108,47 @@ int __init ftrace_dyn_arch_init(void) 
{

	return 0;

}



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent)

{

	unsigned long old;

	unsigned long return_hooker = (unsigned long)&return_to_handler;



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

		return;



	old = *parent;



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

		*parent = return_hooker;

}



static int ftrace_modify_graph_caller(bool enable)

{

	u32 branch, nop;

	unsigned long pc, func;

	extern void ftrace_graph_call(void);



	pc = (unsigned long)&ftrace_graph_call;

	func = (unsigned long)&ftrace_graph_caller;



	nop = larch_insn_gen_nop();

	branch = larch_insn_gen_b(pc, func);



	if (enable)

		return ftrace_modify_code(pc, nop, branch, true);

	else

		return ftrace_modify_code(pc, branch, nop, true);

}



int ftrace_enable_ftrace_graph_caller(void)

{

	return ftrace_modify_graph_caller(true);

}



int ftrace_disable_ftrace_graph_caller(void)

{

	return ftrace_modify_graph_caller(false);

}

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

arch/loongarch/kernel/inst.c

+24 −0
Original line number Diff line number Diff line
@@ -55,6 +55,30 @@ u32 larch_insn_gen_nop(void) 
	return INSN_NOP;

}



u32 larch_insn_gen_b(unsigned long pc, unsigned long dest)

{

	long offset = dest - pc;

	unsigned int immediate_l, immediate_h;

	union loongarch_instruction insn;



	if ((offset & 3) || offset < -SZ_128M || offset >= SZ_128M) {

		pr_warn("The generated b instruction is out of range.\n");

		return INSN_BREAK;

	}



	offset >>= 2;



	immediate_l = offset & 0xffff;

	offset >>= 16;

	immediate_h = offset & 0x3ff;



	insn.reg0i26_format.opcode = b_op;

	insn.reg0i26_format.immediate_l = immediate_l;

	insn.reg0i26_format.immediate_h = immediate_h;



	return insn.word;

}



u32 larch_insn_gen_bl(unsigned long pc, unsigned long dest)

{

	long offset = dest - pc;

arch/loongarch/kernel/mcount_dyn.S

+33 −0
Original line number Diff line number Diff line
@@ -57,6 +57,11 @@ SYM_CODE_START(ftrace_common) 


SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)

	bl		ftrace_stub

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL)

	nop				/* b ftrace_graph_caller */

#endif



/*

 * As we didn't use S series regs in this assmembly code and all calls

 * are C function which will save S series regs by themselves, there is
@@ -83,3 +88,31 @@ SYM_CODE_START(ftrace_caller) 
	ftrace_regs_entry

	b		ftrace_common

SYM_CODE_END(ftrace_caller)



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

SYM_CODE_START(ftrace_graph_caller)

	PTR_L		a0, sp, PT_ERA

	PTR_ADDI	a0, a0, -8	/* arg0: self_addr */

	PTR_ADDI	a1, sp, PT_R1	/* arg1: parent */

	bl		prepare_ftrace_return

	b		ftrace_common_return

SYM_CODE_END(ftrace_graph_caller)



SYM_CODE_START(return_to_handler)

	/* Save return value regs */

	PTR_ADDI 	sp, sp, -2 * SZREG

	PTR_S		a0, sp, 0

	PTR_S		a1, sp, SZREG



	move		a0, zero

	bl		ftrace_return_to_handler

	move		ra, a0



	/* Restore return value regs */

	PTR_L		a0, sp, 0

	PTR_L		a1, sp, SZREG

	PTR_ADDI 	sp, sp, 2 * SZREG



	jr		ra

SYM_CODE_END(return_to_handler)

#endif