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Commit 4984912e authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
Browse files

perf probe: Query basic types from debuginfo 



Query the basic type information (byte-size and signed-flag) from
debuginfo and pass that to kprobe-tracer. This is especially useful
for tracing the members of data structure, because each member has
different byte-size on the memory.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100412171715.3790.23730.stgit@localhost6.localdomain6>
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 93ccae7a

tools/perf/util/probe-event.c

+9 −0
Original line number Diff line number Diff line
@@ -740,6 +740,13 @@ static int synthesize_kprobe_trace_arg(struct kprobe_trace_arg *arg, 
		buf += ret;

		buflen -= ret;

	}

	/* Print argument type */

	if (arg->type) {

		ret = e_snprintf(buf, buflen, ":%s", arg->type);

		if (ret <= 0)

			return ret;

		buf += ret;

	}



	return buf - tmp;

}
@@ -848,6 +855,8 @@ void clear_kprobe_trace_event(struct kprobe_trace_event *tev) 
			free(tev->args[i].name);

		if (tev->args[i].value)

			free(tev->args[i].value);

		if (tev->args[i].type)

			free(tev->args[i].type);

		ref = tev->args[i].ref;

		while (ref) {

			next = ref->next;

tools/perf/util/probe-event.h

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ struct kprobe_trace_arg_ref { 
struct kprobe_trace_arg {

	char				*name;	/* Argument name */

	char				*value;	/* Base value */

	char				*type;	/* Type name */

	struct kprobe_trace_arg_ref	*ref;	/* Referencing offset */

};

tools/perf/util/probe-finder.c

+70 −8
Original line number Diff line number Diff line
@@ -84,6 +84,9 @@ const char *x86_64_regs_table[X86_64_MAX_REGS] = { 
#define arch_regs_table x86_32_regs_table

#endif



/* Kprobe tracer basic type is up to u64 */

#define MAX_BASIC_TYPE_BITS	64



/* Return architecture dependent register string (for kprobe-tracer) */

static const char *get_arch_regstr(unsigned int n)

{
@@ -230,6 +233,31 @@ static Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem) 
	return die_mem;

}



static bool die_is_signed_type(Dwarf_Die *tp_die)

{

	Dwarf_Attribute attr;

	Dwarf_Word ret;



	if (dwarf_attr(tp_die, DW_AT_encoding, &attr) == NULL ||

	    dwarf_formudata(&attr, &ret) != 0)

		return false;



	return (ret == DW_ATE_signed_char || ret == DW_ATE_signed ||

		ret == DW_ATE_signed_fixed);

}



static int die_get_byte_size(Dwarf_Die *tp_die)

{

	Dwarf_Attribute attr;

	Dwarf_Word ret;



	if (dwarf_attr(tp_die, DW_AT_byte_size, &attr) == NULL ||

	    dwarf_formudata(&attr, &ret) != 0)

		return 0;



	return (int)ret;

}



/* Return values for die_find callbacks */

enum {

	DIE_FIND_CB_FOUND = 0,		/* End of Search */
@@ -406,13 +434,42 @@ static void convert_location(Dwarf_Op *op, struct probe_finder *pf) 
	}

}



static void convert_variable_type(Dwarf_Die *vr_die,

				  struct kprobe_trace_arg *targ)

{

	Dwarf_Die type;

	char buf[16];

	int ret;



	if (die_get_real_type(vr_die, &type) == NULL)

		die("Failed to get a type information of %s.",

		    dwarf_diename(vr_die));



	ret = die_get_byte_size(&type) * 8;

	if (ret) {

		/* Check the bitwidth */

		if (ret > MAX_BASIC_TYPE_BITS) {

			pr_warning("  Warning: %s exceeds max-bitwidth."

				   " Cut down to %d bits.\n",

				   dwarf_diename(&type), MAX_BASIC_TYPE_BITS);

			ret = MAX_BASIC_TYPE_BITS;

		}



		ret = snprintf(buf, 16, "%c%d",

			       die_is_signed_type(&type) ? 's' : 'u', ret);

		if (ret < 0 || ret >= 16)

			die("Failed to convert variable type.");

		targ->type = xstrdup(buf);

	}

}



static void convert_variable_fields(Dwarf_Die *vr_die, const char *varname,

				    struct perf_probe_arg_field *field,

				    struct kprobe_trace_arg_ref **ref_ptr)

				    struct kprobe_trace_arg_ref **ref_ptr,

				    Dwarf_Die *die_mem)

{

	struct kprobe_trace_arg_ref *ref = *ref_ptr;

	Dwarf_Attribute attr;

	Dwarf_Die member;

	Dwarf_Die type;

	Dwarf_Word offs;
@@ -450,26 +507,27 @@ static void convert_variable_fields(Dwarf_Die *vr_die, const char *varname, 
			die("Structure on a register is not supported yet.");

	}



	if (die_find_member(&type, field->name, &member) == NULL)

	if (die_find_member(&type, field->name, die_mem) == NULL)

		die("%s(tyep:%s) has no member %s.", varname,

		    dwarf_diename(&type), field->name);



	/* Get the offset of the field */

	if (dwarf_attr(&member, DW_AT_data_member_location, &attr) == NULL ||

	if (dwarf_attr(die_mem, DW_AT_data_member_location, &attr) == NULL ||

	    dwarf_formudata(&attr, &offs) != 0)

		die("Failed to get the offset of %s.", field->name);

	ref->offset += (long)offs;



	/* Converting next field */

	if (field->next)

		convert_variable_fields(&member, field->name, field->next,

					&ref);

		convert_variable_fields(die_mem, field->name, field->next,

					&ref, die_mem);

}



/* Show a variables in kprobe event format */

static void convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)

{

	Dwarf_Attribute attr;

	Dwarf_Die die_mem;

	Dwarf_Op *expr;

	size_t nexpr;

	int ret;
@@ -483,9 +541,13 @@ static void convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf) 


	convert_location(expr, pf);



	if (pf->pvar->field)

	if (pf->pvar->field) {

		convert_variable_fields(vr_die, pf->pvar->var,

					pf->pvar->field, &pf->tvar->ref);

					pf->pvar->field, &pf->tvar->ref,

					&die_mem);

		vr_die = &die_mem;

	}

	convert_variable_type(vr_die, pf->tvar);

	/* *expr will be cached in libdw. Don't free it. */

	return ;

error: