1 files changed, 31 insertions, 8 deletions

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 5a46be968c0b..c04405296e5b 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -273,12 +273,15 @@ static struct probe_trace_arg_ref *alloc_trace_arg_ref(long offs)
 /*
  * Convert a location into trace_arg.
  * If tvar == NULL, this just checks variable can be converted.
+ * If fentry == true and vr_die is a parameter, do huristic search
+ * for the location fuzzed by function entry mcount.
  */
 static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
-				     Dwarf_Op *fb_ops,
+				     Dwarf_Op *fb_ops, Dwarf_Die *sp_die,
 				     struct probe_trace_arg *tvar)
 {
 	Dwarf_Attribute attr;
+	Dwarf_Addr tmp = 0;
 	Dwarf_Op *op;
 	size_t nops;
 	unsigned int regn;
@@ -291,12 +294,29 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
 		goto static_var;
 
 	/* TODO: handle more than 1 exprs */
-	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL ||
-	    dwarf_getlocation_addr(&attr, addr, &op, &nops, 1) <= 0 ||
-	    nops == 0) {
-		/* TODO: Support const_value */
+	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL)
+		return -EINVAL;	/* Broken DIE ? */
+	if (dwarf_getlocation_addr(&attr, addr, &op, &nops, 1) <= 0) {
+		ret = dwarf_entrypc(sp_die, &tmp);
+		if (ret || addr != tmp ||
+		    dwarf_tag(vr_die) != DW_TAG_formal_parameter ||
+		    dwarf_highpc(sp_die, &tmp))
+			return -ENOENT;
+		/*
+		 * This is fuzzed by fentry mcount. We try to find the
+		 * parameter location at the earliest address.
+		 */
+		for (addr += 1; addr <= tmp; addr++) {
+			if (dwarf_getlocation_addr(&attr, addr, &op,
+						   &nops, 1) > 0)
+				goto found;
+		}
 		return -ENOENT;
 	}
+found:
+	if (nops == 0)
+		/* TODO: Support const_value */
+		return -ENOENT;
 
 	if (op->atom == DW_OP_addr) {
 static_var:
@@ -600,7 +620,7 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
 		 dwarf_diename(vr_die));
 
 	ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
-					pf->tvar);
+					&pf->sp_die, pf->tvar);
 	if (ret == -ENOENT)
 		pr_err("Failed to find the location of %s at this address.\n"
 		       " Perhaps, it has been optimized out.\n", pf->pvar->var);
@@ -1148,13 +1168,15 @@ struct local_vars_finder {
 static int copy_variables_cb(Dwarf_Die *die_mem, void *data)
 {
 	struct local_vars_finder *vf = data;
+	struct probe_finder *pf = vf->pf;
 	int tag;
 
 	tag = dwarf_tag(die_mem);
 	if (tag == DW_TAG_formal_parameter ||
 	    tag == DW_TAG_variable) {
 		if (convert_variable_location(die_mem, vf->pf->addr,
-					      vf->pf->fb_ops, NULL) == 0) {
+					      vf->pf->fb_ops, &pf->sp_die,
+					      NULL) == 0) {
 			vf->args[vf->nargs].var = (char *)dwarf_diename(die_mem);
 			if (vf->args[vf->nargs].var == NULL) {
 				vf->ret = -ENOMEM;
@@ -1302,7 +1324,8 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
 	if (tag == DW_TAG_formal_parameter ||
 	    tag == DW_TAG_variable) {
 		ret = convert_variable_location(die_mem, af->pf.addr,
-						af->pf.fb_ops, NULL);
+						af->pf.fb_ops, &af->pf.sp_die,
+						NULL);
 		if (ret == 0) {
 			ret = die_get_varname(die_mem, buf, MAX_VAR_LEN);
 			pr_debug2("Add new var: %s\n", buf);