From 3280cb41768a713012e9c7bd3ec9ccbeed0fb508 Mon Sep 17 00:00:00 2001
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Date: Thu, 24 Jun 2021 10:01:27 -0300
Subject: [PATCH] core: Make parameter->name a real string

For the threaded code we want to access strings in tags at the same time
that the string table may grow in another thread making the previous
pointer invalid, so, to avoid excessive locking, use plain strings.

The way the tools work will either consume the just produced CU straight
away or keep just one copy of each data structure when we keep all CUs
in memory, so lets try stopping using strings_t for strings.

For the parameter->name case we get the bonus of removing a user of
dwarves__active_loader.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 btf_encoder.c     | 4 ++--
 btf_loader.c      | 2 +-
 ctracer.c         | 5 ++---
 dwarf_loader.c    | 2 +-
 dwarves.h         | 9 ++++-----
 dwarves_fprintf.c | 2 +-
 syscse.c          | 3 +--
 7 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/btf_encoder.c b/btf_encoder.c
index 2ed7217..bfdc304 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -541,7 +541,7 @@ static int32_t btf_encoder__add_func_proto(struct btf_encoder *encoder, struct c
 	/* add parameters */
 	param_idx = 0;
 	ftype__for_each_parameter(ftype, param) {
-		const char *name = dwarves__active_loader->strings__ptr(cu, param->name);
+		const char *name = parameter__name(param);
 
 		type_id = param->tag.type == 0 ? 0 : type_id_off + param->tag.type;
 		++param_idx;
@@ -1135,7 +1135,7 @@ static bool has_arg_names(struct cu *cu, struct ftype *ftype)
 	const char *name;
 
 	ftype__for_each_parameter(ftype, param) {
-		name = dwarves__active_loader->strings__ptr(cu, param->name);
+		name = parameter__name(param);
 		if (name == NULL)
 			return false;
 	}
diff --git a/btf_loader.c b/btf_loader.c
index 660125e..8eb9206 100644
--- a/btf_loader.c
+++ b/btf_loader.c
@@ -69,7 +69,7 @@ static int cu__load_ftype(struct cu *cu, struct ftype *proto, uint32_t tag, cons
 				goto out_free_parameters;
 			p->tag.tag  = DW_TAG_formal_parameter;
 			p->tag.type = param->type;
-			p->name	    = param->name_off;
+			p->name	    = cu__btf_str(cu, param->name_off);
 			ftype__add_parameter(proto, p);
 		}
 	}
diff --git a/ctracer.c b/ctracer.c
index e244fe6..350e74c 100644
--- a/ctracer.c
+++ b/ctracer.c
@@ -698,14 +698,13 @@ static int function__emit_probes(struct function *func, uint32_t function_id,
 			continue;
 
 		if (member != NULL)
-			fprintf(fp_methods, "\tif ($%s)\n\t",
-				parameter__name(pos, cu));
+			fprintf(fp_methods, "\tif ($%s)\n\t", parameter__name(pos));
 
 		fprintf(fp_methods,
 			"\tctracer__method_hook(%d, %d, $%s%s%s, %d);\n",
 			probe_type,
 			function_id,
-			parameter__name(pos, cu),
+			parameter__name(pos),
 			member ? "->" : "", member ?: "",
 			class__size(mini_class));
 		break;
diff --git a/dwarf_loader.c b/dwarf_loader.c
index 5a149cb..5c60a12 100644
--- a/dwarf_loader.c
+++ b/dwarf_loader.c
@@ -913,7 +913,7 @@ static struct parameter *parameter__new(Dwarf_Die *die, struct cu *cu)
 
 	if (parm != NULL) {
 		tag__init(&parm->tag, cu, die);
-		parm->name = strings__add(strings, attr_string(die, DW_AT_name));
+		parm->name = strdup_attr_string(die, DW_AT_name);
 	}
 
 	return parm;
diff --git a/dwarves.h b/dwarves.h
index b66bf7c..94a6f18 100644
--- a/dwarves.h
+++ b/dwarves.h
@@ -720,8 +720,8 @@ size_t lexblock__fprintf(const struct lexblock *lexblock, const struct cu *cu,
 			 const struct conf_fprintf *conf, FILE *fp);
 
 struct parameter {
-	struct tag	 tag;
-	strings_t	 name;
+	struct tag tag;
+	const char *name;
 };
 
 static inline struct parameter *tag__parameter(const struct tag *tag)
@@ -729,10 +729,9 @@ static inline struct parameter *tag__parameter(const struct tag *tag)
 	return (struct parameter *)tag;
 }
 
-static inline const char *parameter__name(const struct parameter *parm,
-					  const struct cu *cu)
+static inline const char *parameter__name(const struct parameter *parm)
 {
-	return cu__string(cu, parm->name);
+	return parm->name;
 }
 
 /*
diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c
index 37537ca..b635685 100644
--- a/dwarves_fprintf.c
+++ b/dwarves_fprintf.c
@@ -1084,7 +1084,7 @@ size_t ftype__fprintf_parms(const struct ftype *ftype,
 						   indent, tabs);
 		} else
 			first_parm = 0;
-		name = conf->no_parm_names ? NULL : parameter__name(pos, cu);
+		name = conf->no_parm_names ? NULL : parameter__name(pos);
 		type = cu__type(cu, pos->tag.type);
 		if (type == NULL) {
 			snprintf(sbf, sizeof(sbf),
diff --git a/syscse.c b/syscse.c
index 33fe65e..5d2c6fd 100644
--- a/syscse.c
+++ b/syscse.c
@@ -77,8 +77,7 @@ static void emit_wrapper(struct function *f, struct cu *cu)
 					printf("wrap_%s:\n", name);
 					needs_wrapper = 1;
 				}
-				zero_extend(regparm, bt, cu,
-					    parameter__name(parm, cu));
+				zero_extend(regparm, bt, cu, parameter__name(parm));
 			}
 		}
 		++regparm;