path: root/src/ldso
diff options
authorRich Felker <>2015-03-06 13:27:08 -0500
committerRich Felker <>2015-03-06 13:27:08 -0500
commitbd67959f3ad5049c35af0a0e2f8f1a1e60577a49 (patch)
treee902b7ed8e160789cfc372d25dfd6cbaa0e1492c /src/ldso
parent2b42c8cb37a3ef115bd04de8637078e43cd72f37 (diff)
fix over-alignment of TLS, insufficient builtin TLS on 64-bit archs
a conservative estimate of 4*sizeof(size_t) was used as the minimum alignment for thread-local storage, despite the only requirements being alignment suitable for struct pthread and void* (which struct pthread already contains). additional alignment required by the application or libraries is encoded in their headers and is already applied. over-alignment prevented the builtin_tls array from ever being used in dynamic-linked programs on 64-bit archs, thereby requiring allocation at startup even in programs with no TLS of their own.
Diffstat (limited to 'src/ldso')
1 files changed, 8 insertions, 2 deletions
diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index 0bdc988c..ca101993 100644
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -122,6 +122,13 @@ void __init_libc(char **, char *);
const char *__libc_get_version(void);
+static struct builtin_tls {
+ char c;
+ struct pthread pt;
+ void *space[16];
+} builtin_tls[1];
+#define MIN_TLS_ALIGN offsetof(struct builtin_tls, pt)
static struct dso *head, *tail, *ldso, *fini_head;
static char *env_path, *sys_path;
static unsigned long long gencnt;
@@ -132,10 +139,9 @@ static int noload;
static jmp_buf *rtld_fail;
static pthread_rwlock_t lock;
static struct debug debug;
-static size_t tls_cnt, tls_offset, tls_align = 4*sizeof(size_t);
+static size_t tls_cnt, tls_offset, tls_align = MIN_TLS_ALIGN;
static size_t static_tls_cnt;
static pthread_mutex_t init_fini_lock = { ._m_type = PTHREAD_MUTEX_RECURSIVE };
-static long long builtin_tls[(sizeof(struct pthread) + 64)/sizeof(long long)];
struct debug *_dl_debug_addr = &debug;