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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.
This commit is contained in:
Rich Felker 2015-03-06 13:27:08 -05:00
parent 2b42c8cb37
commit bd67959f3a
2 changed files with 16 additions and 4 deletions
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10
src/env/__init_tls.c vendored
View File

@ -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);

10
src/ldso/dynlink.c
View File

@ -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;