[PATCH 47/59] elf: Fix tunable handing with clang

[Adhemerval Zanella]

Recent clang version optimizes some loops contructions to strlen [1],
which might generate function calls when self-relocation is not
already done (on tunable parsing).  Use an out-of-line function
with __attribute_optimization_barrier__ to avoid this.

[1] https://github.com/llvm/llvm-project/pull/132572/commits/facd7dfc80d655fe49baf4bf27e144a4c890a149
---
 elf/dl-printf.c   |  1 +
 elf/dl-tunables.c | 13 +++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/elf/dl-printf.c b/elf/dl-printf.c
index ebfc7eee86..77551f99eb 100644
--- a/elf/dl-printf.c
+++ b/elf/dl-printf.c
@@ -35,6 +35,7 @@
 
 /* The function might be called before the process is self-relocated.  */
 static size_t
+__attribute_optimization_barrier__
 _dl_debug_strlen (const char *s)
 {
   const char *p = s;
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index f65480690a..f145481d55 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -37,6 +37,16 @@
 #define TUNABLES_INTERNAL 1
 #include "dl-tunables.h"
 
+/* The function might be called before the process is self-relocated.  */
+static size_t
+__attribute_optimization_barrier__
+_dl_strlen (const char *s)
+{
+  const char *p = s;
+  for (; *s != '\0'; s++);
+  return s - p;
+}
+
 static char **
 get_next_env (char **envp, char **name, char **val, char ***prev_envp)
 {
@@ -324,9 +334,8 @@ __tunables_init (char **envp)
 
 	  if (tunable_is_name (name, envname))
 	    {
-	      size_t envvallen = 0;
 	      /* The environment variable is always null-terminated.  */
-	      for (const char *p = envval; *p != '\0'; p++, envvallen++);
+	      size_t envvallen = _dl_strlen (envval);
 
 	      tunables_env_alias[i] =
 		(struct tunable_toset_t) { cur, envval, envvallen };
-- 
2.43.0