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authorRich Felker <dalias@aerifal.cx>2015-03-06 13:27:08 -0500
committerRich Felker <dalias@aerifal.cx>2015-03-06 13:27:08 -0500
commitbd67959f3ad5049c35af0a0e2f8f1a1e60577a49 (patch)
treee902b7ed8e160789cfc372d25dfd6cbaa0e1492c /src
parent2b42c8cb37a3ef115bd04de8637078e43cd72f37 (diff)
downloadmusl-bd67959f3ad5049c35af0a0e2f8f1a1e60577a49.tar.gz
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')
-rw-r--r--src/env/__init_tls.c10
-rw-r--r--src/ldso/dynlink.c10
2 files changed, 16 insertions, 4 deletions
diff --git a/src/env/__init_tls.c b/src/env/__init_tls.c
index ddc2a736..b0dad429 100644
--- a/src/env/__init_tls.c
+++ b/src/env/__init_tls.c
@@ -2,6 +2,7 @@
#include <limits.h>
#include <sys/mman.h>
#include <string.h>
+#include <stddef.h>
#include "pthread_impl.h"
#include "libc.h"
#include "atomic.h"
@@ -22,7 +23,12 @@ int __init_tp(void *p)
#ifndef SHARED
-static long long builtin_tls[(sizeof(struct pthread) + 64)/sizeof(long long)];
+static struct builtin_tls {
+ char c;
+ struct pthread pt;
+ void *space[16];
+} builtin_tls[1];
+#define MIN_TLS_ALIGN offsetof(struct builtin_tls, pt)
struct tls_image {
void *image;
@@ -86,7 +92,7 @@ void __init_tls(size_t *aux)
}
T.size += (-T.size - (uintptr_t)T.image) & (T.align-1);
- if (T.align < 4*sizeof(size_t)) T.align = 4*sizeof(size_t);
+ if (T.align < MIN_TLS_ALIGN) T.align = MIN_TLS_ALIGN;
libc.tls_size = 2*sizeof(void *)+T.size+T.align+sizeof(struct pthread);
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;