Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit dd686eb1 authored by Rabin Vincent's avatar Rabin Vincent
Browse files

ARM: ftrace: graph tracer + dynamic ftrace 



Support the graph tracer + dynamic ftrace combination on ARM.

Signed-off-by: default avatarRabin Vincent <rabin@rab.in>
parent 376cfa87

arch/arm/kernel/entry-common.S

+12 −0
Original line number Diff line number Diff line
@@ -183,12 +183,24 @@ ENDPROC(ret_from_fork) 
ftrace_call\suffix:

	bl	ftrace_stub



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	.globl ftrace_graph_call\suffix

ftrace_graph_call\suffix:

	mov	r0, r0

#endif



	mcount_exit

.endm



.macro __ftrace_graph_caller

	sub	r0, fp, #4		@ &lr of instrumented routine (&parent)

#ifdef CONFIG_DYNAMIC_FTRACE

	@ called from __ftrace_caller, saved in mcount_enter

	ldr	r1, [sp, #16]		@ instrumented routine (func)

#else

	@ called from __mcount, untouched in lr

	mov	r1, lr			@ instrumented routine (func)

#endif

	sub	r1, r1, #MCOUNT_INSN_SIZE

	mov	r2, fp			@ frame pointer

	bl	prepare_ftrace_return

arch/arm/kernel/ftrace.c

+64 −5
Original line number Diff line number Diff line
@@ -60,9 +60,9 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) 
}

#endif



/* construct a branch (BL) instruction to addr */

#ifdef CONFIG_THUMB2_KERNEL

static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)

static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,

				       bool link)

{

	unsigned long s, j1, j2, i1, i2, imm10, imm11;

	unsigned long first, second;
@@ -84,15 +84,22 @@ static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) 
	j2 = (!i2) ^ s;



	first = 0xf000 | (s << 10) | imm10;

	second = 0xd000 | (j1 << 13) | (j2 << 11) | imm11;

	second = 0x9000 | (j1 << 13) | (j2 << 11) | imm11;

	if (link)

		second |= 1 << 14;



	return (second << 16) | first;

}

#else

static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)

static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,

				       bool link)

{

	unsigned long opcode = 0xea000000;

	long offset;



	if (link)

		opcode |= 1 << 24;



	offset = (long)addr - (long)(pc + 8);

	if (unlikely(offset < -33554432 || offset > 33554428)) {

		/* Can't generate branches that far (from ARM ARM). Ftrace
@@ -104,10 +111,15 @@ static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) 


	offset = (offset >> 2) & 0x00ffffff;



	return 0xeb000000 | offset;

	return opcode | offset;

}

#endif



static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)

{

	return ftrace_gen_branch(pc, addr, true);

}



static int ftrace_modify_code(unsigned long pc, unsigned long old,

			      unsigned long new)

{
@@ -226,4 +238,51 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
		*parent = old;

	}

}



#ifdef CONFIG_DYNAMIC_FTRACE

extern unsigned long ftrace_graph_call;

extern unsigned long ftrace_graph_call_old;

extern void ftrace_graph_caller_old(void);



static int __ftrace_modify_caller(unsigned long *callsite,

				  void (*func) (void), bool enable)

{

	unsigned long caller_fn = (unsigned long) func;

	unsigned long pc = (unsigned long) callsite;

	unsigned long branch = ftrace_gen_branch(pc, caller_fn, false);

	unsigned long nop = 0xe1a00000;	/* mov r0, r0 */

	unsigned long old = enable ? nop : branch;

	unsigned long new = enable ? branch : nop;



	return ftrace_modify_code(pc, old, new);

}



static int ftrace_modify_graph_caller(bool enable)

{

	int ret;



	ret = __ftrace_modify_caller(&ftrace_graph_call,

				     ftrace_graph_caller,

				     enable);



#ifdef CONFIG_OLD_MCOUNT

	if (!ret)

		ret = __ftrace_modify_caller(&ftrace_graph_call_old,

					     ftrace_graph_caller_old,

					     enable);

#endif



	return ret;

}



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_DYNAMIC_FTRACE */

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */