| Message ID | 86ff3e8442162298b82734abe00ed28a84f006f2.1719420465.git.fweimer@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | elf: Avoid re-initializing already allocated TLS in dlopen (bug 31717) | expand |
On 6/26/24 12:50 PM, Florian Weimer wrote: > --- > elf/dl-tls.c | 10 +++------- > elf/rtld.c | 2 +- > nptl/allocatestack.c | 2 +- > sysdeps/generic/ldsodefs.h | 13 ++++++++++++- > 4 files changed, 17 insertions(+), 10 deletions(-) This is just a cleanup in preparation for the additional use of main_thread. LGTM. Minor note about comments and summaries near code. Reviewed-by: Carlos O'Donell <carlos@redhat.com> > diff --git a/elf/dl-tls.c b/elf/dl-tls.c > index 670dbc42fc..67ce4771e3 100644 > --- a/elf/dl-tls.c > +++ b/elf/dl-tls.c > @@ -514,12 +514,8 @@ _dl_resize_dtv (dtv_t *dtv, size_t max_modid) > } > > > -/* Allocate initial TLS. RESULT should be a non-NULL pointer to storage > - for the TLS space. The DTV may be resized, and so this function may > - call malloc to allocate that space. The loader's GL(dl_load_tls_lock) > - is taken when manipulating global TLS-related data in the loader. */ OK. My preference here is for ldsodefs.h comment to be here. > void * > -_dl_allocate_tls_init (void *result, bool init_tls) > +_dl_allocate_tls_init (void *result, bool main_thread) > { > if (result == NULL) > /* The memory allocation failed. */ > @@ -598,7 +594,7 @@ _dl_allocate_tls_init (void *result, bool init_tls) > because it would already be set by the audit setup. However, > subsequent thread creation would need to follow the default > behaviour. */ > - if (map->l_ns != LM_ID_BASE && !init_tls) > + if (map->l_ns != LM_ID_BASE && main_thread) OK. > continue; > memset (__mempcpy (dest, map->l_tls_initimage, > map->l_tls_initimage_size), '\0', > @@ -626,7 +622,7 @@ _dl_allocate_tls (void *mem) > { > return _dl_allocate_tls_init (mem == NULL > ? _dl_allocate_tls_storage () > - : allocate_dtv (mem), true); > + : allocate_dtv (mem), false); OK. > } > rtld_hidden_def (_dl_allocate_tls) > > diff --git a/elf/rtld.c b/elf/rtld.c > index e9525ea987..da0d115c69 100644 > --- a/elf/rtld.c > +++ b/elf/rtld.c > @@ -2336,7 +2336,7 @@ dl_main (const ElfW(Phdr) *phdr, > into the main thread's TLS area, which we allocated above. > Note: thread-local variables must only be accessed after completing > the next step. */ > - _dl_allocate_tls_init (tcbp, false); > + _dl_allocate_tls_init (tcbp, true); OK. Yes, definitely, we're in rtld. > > /* And finally install it for the main thread. */ > if (! __rtld_tls_init_tp_called) > diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c > index f35a8369bd..2cb562f8ea 100644 > --- a/nptl/allocatestack.c > +++ b/nptl/allocatestack.c > @@ -139,7 +139,7 @@ get_cached_stack (size_t *sizep, void **memp) > memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t)); > > /* Re-initialize the TLS. */ > - _dl_allocate_tls_init (TLS_TPADJ (result), true); > + _dl_allocate_tls_init (TLS_TPADJ (result), false); OK. > > return result; > } > diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h > index 50f58a60e3..2bccac3f7c 100644 > --- a/sysdeps/generic/ldsodefs.h > +++ b/sysdeps/generic/ldsodefs.h > @@ -1203,7 +1203,18 @@ extern void _dl_allocate_static_tls (struct link_map *map) attribute_hidden; > /* These are internal entry points to the two halves of _dl_allocate_tls, > only used within rtld.c itself at startup time. */ > extern void *_dl_allocate_tls_storage (void) attribute_hidden; > -extern void *_dl_allocate_tls_init (void *, bool); > + > + > +/* Allocate initial TLS. RESULT should be a non-NULL pointer to storage > + for the TLS space. The DTV may be resized, and so this function may > + call malloc to allocate that space. The loader's GL(dl_load_tls_lock) > + is taken when manipulating global TLS-related data in the loader. > + > + If MAIN_THREAD, this is the first call during process > + initialization. In this case, TLS initialization for secondary > + (audit) namespaces is skipped because that has already been handled > + by dlopen. */ OK. I see why we want this here, in that a developer of glibc would want to pull up the comment as they call the internal API, but my concern is that this starts to deviate from the implementation. I suggest moving this into the location of the code and put a summary here. > +extern void *_dl_allocate_tls_init (void *result, bool main_thread); > rtld_hidden_proto (_dl_allocate_tls_init) > > /* True if the TCB has been set up. */
* Carlos O'Donell: >> -/* Allocate initial TLS. RESULT should be a non-NULL pointer to storage >> - for the TLS space. The DTV may be resized, and so this function may >> - call malloc to allocate that space. The loader's GL(dl_load_tls_lock) >> - is taken when manipulating global TLS-related data in the loader. */ > > OK. My preference here is for ldsodefs.h comment to be here. I'm going to post a v6 with these changes. I don't have a strong preference (just a slight one), especially it's not always obvious which header would contain the function comment. Thanks, Florian
diff --git a/elf/dl-tls.c b/elf/dl-tls.c index 670dbc42fc..67ce4771e3 100644 --- a/elf/dl-tls.c +++ b/elf/dl-tls.c @@ -514,12 +514,8 @@ _dl_resize_dtv (dtv_t *dtv, size_t max_modid) } -/* Allocate initial TLS. RESULT should be a non-NULL pointer to storage - for the TLS space. The DTV may be resized, and so this function may - call malloc to allocate that space. The loader's GL(dl_load_tls_lock) - is taken when manipulating global TLS-related data in the loader. */ void * -_dl_allocate_tls_init (void *result, bool init_tls) +_dl_allocate_tls_init (void *result, bool main_thread) { if (result == NULL) /* The memory allocation failed. */ @@ -598,7 +594,7 @@ _dl_allocate_tls_init (void *result, bool init_tls) because it would already be set by the audit setup. However, subsequent thread creation would need to follow the default behaviour. */ - if (map->l_ns != LM_ID_BASE && !init_tls) + if (map->l_ns != LM_ID_BASE && main_thread) continue; memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size), '\0', @@ -626,7 +622,7 @@ _dl_allocate_tls (void *mem) { return _dl_allocate_tls_init (mem == NULL ? _dl_allocate_tls_storage () - : allocate_dtv (mem), true); + : allocate_dtv (mem), false); } rtld_hidden_def (_dl_allocate_tls) diff --git a/elf/rtld.c b/elf/rtld.c index e9525ea987..da0d115c69 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -2336,7 +2336,7 @@ dl_main (const ElfW(Phdr) *phdr, into the main thread's TLS area, which we allocated above. Note: thread-local variables must only be accessed after completing the next step. */ - _dl_allocate_tls_init (tcbp, false); + _dl_allocate_tls_init (tcbp, true); /* And finally install it for the main thread. */ if (! __rtld_tls_init_tp_called) diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c index f35a8369bd..2cb562f8ea 100644 --- a/nptl/allocatestack.c +++ b/nptl/allocatestack.c @@ -139,7 +139,7 @@ get_cached_stack (size_t *sizep, void **memp) memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t)); /* Re-initialize the TLS. */ - _dl_allocate_tls_init (TLS_TPADJ (result), true); + _dl_allocate_tls_init (TLS_TPADJ (result), false); return result; } diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 50f58a60e3..2bccac3f7c 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -1203,7 +1203,18 @@ extern void _dl_allocate_static_tls (struct link_map *map) attribute_hidden; /* These are internal entry points to the two halves of _dl_allocate_tls, only used within rtld.c itself at startup time. */ extern void *_dl_allocate_tls_storage (void) attribute_hidden; -extern void *_dl_allocate_tls_init (void *, bool); + + +/* Allocate initial TLS. RESULT should be a non-NULL pointer to storage + for the TLS space. The DTV may be resized, and so this function may + call malloc to allocate that space. The loader's GL(dl_load_tls_lock) + is taken when manipulating global TLS-related data in the loader. + + If MAIN_THREAD, this is the first call during process + initialization. In this case, TLS initialization for secondary + (audit) namespaces is skipped because that has already been handled + by dlopen. */ +extern void *_dl_allocate_tls_init (void *result, bool main_thread); rtld_hidden_proto (_dl_allocate_tls_init) /* True if the TCB has been set up. */