add system for resetting TLS to initial values

this is needed for reused threads in the SIGEV_THREAD timer
notification system, and could be reused elsewhere in the future if
needed, though it should be refactored for such use.

for static linking, __init_tls.c is simply modified to export the TLS
info in a structure with external linkage, rather than using statics.
this perhaps makes the code more clear, since the statics were poorly
named for statics. the new __reset_tls.c is only linked if it is used.

for dynamic linking, the code is in dynlink.c. sharing code with
__copy_tls is not practical since __reset_tls must also re-zero
thread-local bss.

diff --git a/src/env/__init_tls.c b/src/env/__init_tls.c
index a4704f0..5c17681 100644 (file)
--- a/src/env/__init_tls.c
+++ b/src/env/__init_tls.c
@@ -8,29 +8,33 @@
 
 #ifndef SHARED
 
-static void *image;
-static size_t len, size, align;
+struct tls_image {
+       void *image;
+       size_t len, size, align;
+} __static_tls ATTR_LIBC_VISIBILITY;
+
+#define T __static_tls
 
 void *__copy_tls(unsigned char *mem)
 {
        pthread_t td;
-       if (!image) return mem;
+       if (!T.image) return mem;
        void **dtv = (void *)mem;
        dtv[0] = (void *)1;
 #ifdef TLS_ABOVE_TP
        mem += sizeof(void *) * 2;
-       mem += -((uintptr_t)mem + sizeof(struct pthread)) & (align-1);
+       mem += -((uintptr_t)mem + sizeof(struct pthread)) & (T.align-1);
        td = (pthread_t)mem;
        mem += sizeof(struct pthread);
 #else
        mem += libc.tls_size - sizeof(struct pthread);
-       mem -= (uintptr_t)mem & (align-1);
+       mem -= (uintptr_t)mem & (T.align-1);
        td = (pthread_t)mem;
-       mem -= size;
+       mem -= T.size;
 #endif
        td->dtv = dtv;
        dtv[1] = mem;
-       memcpy(mem, image, len);
+       memcpy(mem, T.image, T.len);
        return td;
 }
 
@@ -73,15 +77,15 @@ void __init_tls(size_t *aux)
        }
        if (!tls_phdr) return;
 
-       image = (void *)(base + tls_phdr->p_vaddr);
-       len = tls_phdr->p_filesz;
-       size = tls_phdr->p_memsz;
-       align = tls_phdr->p_align;
+       T.image = (void *)(base + tls_phdr->p_vaddr);
+       T.len = tls_phdr->p_filesz;
+       T.size = tls_phdr->p_memsz;
+       T.align = tls_phdr->p_align;
 
-       size += (-size - (uintptr_t)image) & (align-1);
-       if (align < 4*sizeof(size_t)) align = 4*sizeof(size_t);
+       T.size += (-T.size - (uintptr_t)T.image) & (T.align-1);
+       if (T.align < 4*sizeof(size_t)) T.align = 4*sizeof(size_t);
 
-       libc.tls_size = 2*sizeof(void *)+size+align+sizeof(struct pthread);
+       libc.tls_size = 2*sizeof(void *)+T.size+T.align+sizeof(struct pthread);
 
        mem = __mmap(0, libc.tls_size, PROT_READ|PROT_WRITE,
                MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);

diff --git a/src/env/__reset_tls.c b/src/env/__reset_tls.c
new file mode 100644 (file)
index 0000000..28c4405
--- /dev/null
+++ b/src/env/__reset_tls.c
@@ -0,0 +1,22 @@
+#ifndef SHARED
+
+#include <string.h>
+#include "pthread_impl.h"
+#include "libc.h"
+
+extern struct tls_image {
+       void *image;
+       size_t len, size, align;
+} __static_tls ATTR_LIBC_VISIBILITY;
+
+#define T __static_tls
+
+void __reset_tls()
+{
+       if (!T.size) return;
+       pthread_t self = __pthread_self();
+       memcpy(self->dtv[1], T.image, T.len);
+       memset((char *)self->dtv[1]+T.len, 0, T.size-T.len);
+}
+
+#endif

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index d689f96..fa5ad00 100644 (file)
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -783,6 +783,19 @@ void _dl_debug_state(void)
 {
 }
 
+void __reset_tls()
+{
+       pthread_t self = __pthread_self();
+       struct dso *p;
+       for (p=head; p; p=p->next) {
+               if (!p->tls_id || !self->dtv[p->tls_id]) continue;
+               memcpy(self->dtv[p->tls_id], p->tls_image, p->tls_len);
+               memset((char *)self->dtv[p->tls_id]+p->tls_len, 0,
+                       p->tls_size - p->tls_len);
+               if (p->tls_id == (size_t)self->dtv[0]) break;
+       }
+}
+
 void *__copy_tls(unsigned char *mem)
 {
        pthread_t td;

diff --git a/src/time/timer_create.c b/src/time/timer_create.c
index 2b4619d..ee6a9c9 100644 (file)
--- a/src/time/timer_create.c
+++ b/src/time/timer_create.c
@@ -19,6 +19,8 @@ static void dummy_1(pthread_t self)
 }
 weak_alias(dummy_1, __pthread_tsd_run_dtors);
 
+void __reset_tls();
+
 static void cleanup_fromsig(void *p)
 {
        pthread_t self = __pthread_self();
@@ -28,6 +30,7 @@ static void cleanup_fromsig(void *p)
        self->canceldisable = 0;
        self->cancelasync = 0;
        self->unblock_cancel = 0;
+       __reset_tls();
        longjmp(p, 1);
 }