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Unverified Commit bc1a4c3a authored by Alan Kao's avatar Alan Kao Committed by Palmer Dabbelt
Browse files

riscv/ftrace: Add dynamic function graph tracer support 



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

* ftracer_caller         ==> on/off by ftrace_make_call/ftrace_make_nop
* ftrace_graph_caller
* ftrace_graph_call      ==> on/off by ftrace_en/disable_ftrace_graph_caller
* 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.

Cc: Greentime Hu <greentime@andestech.com>
Signed-off-by: default avatarAlan Kao <alankao@andestech.com>
Signed-off-by: default avatarPalmer Dabbelt <palmer@sifive.com>
parent c15ac4fd

arch/riscv/kernel/ftrace.c

+54 −1
Original line number Diff line number Diff line
@@ -139,4 +139,57 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
		return;

	*parent = return_hooker;

}

#endif
 


#ifdef CONFIG_DYNAMIC_FTRACE

extern void ftrace_graph_call(void);

int ftrace_enable_ftrace_graph_caller(void)

{

	unsigned int call[2];

	static int init_graph = 1;

	int ret;



	make_call(&ftrace_graph_call, &ftrace_stub, call);



	/*

	 * When enabling graph tracer for the first time, ftrace_graph_call

	 * should contains a call to ftrace_stub.  Once it has been disabled,

	 * the 8-bytes at the position becomes NOPs.

	 */

	if (init_graph) {

		ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,

						call);

		init_graph = 0;

	} else {

		ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,

						NULL);

	}



	if (ret)

		return ret;



	return __ftrace_modify_call((unsigned long)&ftrace_graph_call,

				    (unsigned long)&prepare_ftrace_return, true);

}



int ftrace_disable_ftrace_graph_caller(void)

{

	unsigned int call[2];

	int ret;



	make_call(&ftrace_graph_call, &prepare_ftrace_return, call);



	/*

	 * This is to make sure that ftrace_enable_ftrace_graph_caller

	 * did the right thing.

	 */

	ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,

					call);



	if (ret)

		return ret;



	return __ftrace_modify_call((unsigned long)&ftrace_graph_call,

				    (unsigned long)&prepare_ftrace_return, false);

}

#endif /* CONFIG_DYNAMIC_FTRACE */

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

arch/riscv/kernel/mcount-dyn.S

+64 −0
Original line number Diff line number Diff line
@@ -14,18 +14,62 @@ 
	.text



	.macro SAVE_ABI_STATE

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	addi    sp, sp, -48

	sd      s0, 32(sp)

	sd      ra, 40(sp)

	addi    s0, sp, 48

	sd      t0, 24(sp)

	sd      t1, 16(sp)

#ifdef HAVE_FUNCTION_GRAPH_FP_TEST

	sd      t2, 8(sp)

#endif

#else

	addi	sp, sp, -16

	sd	s0, 0(sp)

	sd	ra, 8(sp)

	addi	s0, sp, 16

#endif

	.endm



	.macro RESTORE_ABI_STATE

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	ld	s0, 32(sp)

	ld	ra, 40(sp)

	addi	sp, sp, 48

#else

	ld	ra, 8(sp)

	ld	s0, 0(sp)

	addi	sp, sp, 16

#endif

	.endm



	.macro RESTORE_GRAPH_ARGS

	ld	a0, 24(sp)

	ld	a1, 16(sp)

#ifdef HAVE_FUNCTION_GRAPH_FP_TEST

	ld	a2, 8(sp)

#endif

	.endm



ENTRY(ftrace_graph_caller)

	addi	sp, sp, -16

	sd	s0, 0(sp)

	sd	ra, 8(sp)

	addi	s0, sp, 16

ftrace_graph_call:

	.global ftrace_graph_call

	/*

	 * Calling ftrace_enable/disable_ftrace_graph_caller would overwrite the

	 * call below.  Check ftrace_modify_all_code for details.

	 */

	call	ftrace_stub

	ld	ra, 8(sp)

	ld	s0, 0(sp)

	addi	sp, sp, 16

	ret

ENDPROC(ftrace_graph_caller)



ENTRY(ftrace_caller)

	/*

	 * a0: the address in the caller when calling ftrace_caller
@@ -33,6 +77,20 @@ ENTRY(ftrace_caller) 
	 */

	ld	a1, -8(s0)

	addi	a0, ra, -MCOUNT_INSN_SIZE



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	/*

	 * the graph tracer (specifically, prepare_ftrace_return) needs these

	 * arguments but for now the function tracer occupies the regs, so we

	 * save them in temporary regs to recover later.

	 */

	addi	t0, s0, -8

	mv	t1, a0

#ifdef HAVE_FUNCTION_GRAPH_FP_TEST

	ld	t2, -16(s0)

#endif

#endif



	SAVE_ABI_STATE

ftrace_call:

	.global ftrace_call
@@ -45,6 +103,12 @@ ftrace_call: 
	 * Check ftrace_modify_all_code for details.

	 */

	call	ftrace_stub



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	RESTORE_GRAPH_ARGS

	call	ftrace_graph_caller

#endif



	RESTORE_ABI_STATE

	ret

ENDPROC(ftrace_caller)