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[PATCH][BZ #16046] Static dlopen correction fallout fixes
- From: "Maciej W. Rozycki" <macro at codesourcery dot com>
- To: Roland McGrath <roland at hack dot frob dot com>
- Cc: Ondřej Bílka <neleai at seznam dot cz>, Allan McRae <allan at archlinux dot org>, <libc-alpha at sourceware dot org>
- Date: Wed, 29 Jan 2014 14:59:40 +0000
- Subject: [PATCH][BZ #16046] Static dlopen correction fallout fixes
- Authentication-results: sourceware.org; auth=none
- References: <20131017174710 dot GA4993 at domone dot podge> <20131025210328 dot 39E69746B6 at topped-with-meat dot com> <alpine dot DEB dot 1 dot 10 dot 1310252347350 dot 12843 at tp dot orcam dot me dot uk> <20140116203847 dot GB20838 at domone dot podge> <alpine dot DEB dot 1 dot 10 dot 1401172303320 dot 4268 at tp dot orcam dot me dot uk> <20140117233957 dot 64E307441B at topped-with-meat dot com> <alpine dot DEB dot 1 dot 10 dot 1401271320170 dot 4268 at tp dot orcam dot me dot uk>
On Mon, 27 Jan 2014, Maciej W. Rozycki wrote:
> > 16046 suggests that the status quo today is a regression from 2.18. If
> > that's true, then I think it does need to get fixed in 2.19 so that the
> > user-visible behavior does not differ (except in the intended ways for
> > static executables). Further cleanup could wait until after 2.19, but if
> > it's straightforward then I'd be just as happy to see it done right away.
> > (The 2.19 release manager may feel differently.)
>
> I read the deadline is next Thursday or so; I'll see what I can do.
And here it is. Following your encouragement I decided to include all
updates for all places I have identified so far. Please let me know if
you feel uneasy about any of them and I'll leave these out. Here are
descriptions of the individual changes:
* TLS updates to csu/libc-tls.c -- we now have a proper main map, so
there's no longer a need to create a separate fake one to keep TLS
structures,
* random updates to elf/dl-close.c -- LM_ID_BASE is now a valid name space
ID for static executables as well, so assert that we don't unload the
main map. Similarly dl_nns isn't supposed to be 0 for static
executables anymore,
* actual BZ #16046 fix to elf/dl-iteratephdr.c -- the dl_iterate_phdr
special function for static executables isn't needed anymore, provided
that l_phdr and l_phnum members of the main map have been properly
initialized (done in _dl_non_dynamic_init in elf/dl-support.c now),
* ld.so.cache loader update to elf/dl-load.c --
GL(dl_ns)[LM_ID_BASE]._ns_loaded is now always initialized in static
executables so can become the fallback loader map to check for
DF_1_NODEFLIB, provided that the l_flags_1 member of the main map has
been properly initialized (done in elf/dl-support.c now); this also
ensures previous semantics elsewhere in elf/dl-load.c,
* matching updates to elf/dl-support.c -- to complement the two fixes
above.
Questions or comments? I've looked into turning the program supplied
with the bug report into a proper test case, but the presence of
linux-vdso.so.1 implicitly loaded in one of the static dumps made me
question the ability to make such a test case work reliably. Suggestions
are welcome.
Regression-tested successfully with the mips-linux-gnu target
(big-endian, o32 ABI) -- as the change is target-agnostic I believe this
should provide enough coverage; please shout if you disagree. Also the
test case provided with the bug report produces correct output now:
$ ./dl-iter-static-orig
addr=(nil) name= phdr=0x400034 phnum=5
addr=(nil) name= phdr=(nil) phnum=0
$ ./dl-iter-static-good
addr=(nil) name= phdr=0x400034 phnum=5
$
OK to apply?
2014-01-29 Maciej W. Rozycki <macro@codesourcery.com>
[BZ #16046]
* csu/libc-tls.c (static_map): Remove variable.
(__libc_setup_tls): Use main executable's link map for TLS data.
* elf/dl-close.c (_dl_close_worker) [!SHARED]: Remove special
casing for LM_ID_BASE and GL(dl_nns).
* elf/dl-iteratephdr.c [!SHARED] (dl_iterate_phdr): Remove
function. Alias dl_iterate_phdr to __dl_iterate_phdr.
* elf/dl-load.c (_dl_map_object) [!SHARED]: Remove special
casing for GL(dl_ns)[LM_ID_BASE]._ns_loaded.
* elf/dl-support.c (_dl_main_map): Also initialize l_flags_1
member.
(_dl_non_dynamic_init): Also initialize _dl_main_map's l_phdr and
l_phnum members.
Maciej
glibc-static-dlopen-16046.diff
Index: glibc-fsf-trunk-quilt/csu/libc-tls.c
===================================================================
--- glibc-fsf-trunk-quilt.orig/csu/libc-tls.c 2014-01-29 11:23:16.000000000 +0000
+++ glibc-fsf-trunk-quilt/csu/libc-tls.c 2014-01-29 12:09:13.062013406 +0000
@@ -42,9 +42,6 @@ static struct
struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
} static_slotinfo;
-/* Fake link map for the application. */
-static struct link_map static_map;
-
/* Highest dtv index currently needed. */
size_t _dl_tls_max_dtv_idx;
@@ -162,14 +159,16 @@ __libc_setup_tls (size_t tcbsize, size_t
_dl_static_dtv[0].counter = (sizeof (_dl_static_dtv) / sizeof (_dl_static_dtv[0])) - 2;
// _dl_static_dtv[1].counter = 0; would be needed if not already done
+ struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
+
/* Initialize the TLS block. */
#if TLS_TCB_AT_TP
_dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
- roundup (memsz, align ?: 1));
- static_map.l_tls_offset = roundup (memsz, align ?: 1);
+ main_map->l_tls_offset = roundup (memsz, align ?: 1);
#elif TLS_DTV_AT_TP
_dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
- static_map.l_tls_offset = tcb_offset;
+ main_map->l_tls_offset = tcb_offset;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
@@ -193,19 +192,17 @@ __libc_setup_tls (size_t tcbsize, size_t
if (__builtin_expect (lossage != NULL, 0))
__libc_fatal (lossage);
- /* We have to create a fake link map which normally would be created
- by the dynamic linker. It just has to have enough information to
- make the TLS routines happy. */
- static_map.l_tls_align = align;
- static_map.l_tls_blocksize = memsz;
- static_map.l_tls_initimage = initimage;
- static_map.l_tls_initimage_size = filesz;
- static_map.l_type = lt_executable;
- static_map.l_tls_modid = 1;
+ /* Update the executable's link map with enough information to make
+ the TLS routines happy. */
+ main_map->l_tls_align = align;
+ main_map->l_tls_blocksize = memsz;
+ main_map->l_tls_initimage = initimage;
+ main_map->l_tls_initimage_size = filesz;
+ main_map->l_tls_modid = 1;
init_slotinfo ();
// static_slotinfo.si.slotinfo[1].gen = 0; already zero
- static_slotinfo.si.slotinfo[1].map = &static_map;
+ static_slotinfo.si.slotinfo[1].map = main_map;
memsz = roundup (memsz, align ?: 1);
Index: glibc-fsf-trunk-quilt/elf/dl-close.c
===================================================================
--- glibc-fsf-trunk-quilt.orig/elf/dl-close.c 2014-01-29 11:23:16.000000000 +0000
+++ glibc-fsf-trunk-quilt/elf/dl-close.c 2014-01-29 12:09:13.062013406 +0000
@@ -643,9 +643,7 @@ _dl_close_worker (struct link_map *map)
imap->l_prev->l_next = imap->l_next;
else
{
-#ifdef SHARED
assert (nsid != LM_ID_BASE);
-#endif
ns->_ns_loaded = imap->l_next;
/* Update the pointer to the head of the list
@@ -736,13 +734,7 @@ _dl_close_worker (struct link_map *map)
if (__builtin_expect (ns->_ns_loaded == NULL, 0)
&& nsid == GL(dl_nns) - 1)
do
- {
- --GL(dl_nns);
-#ifndef SHARED
- if (GL(dl_nns) == 0)
- break;
-#endif
- }
+ --GL(dl_nns);
while (GL(dl_ns)[GL(dl_nns) - 1]._ns_loaded == NULL);
/* Notify the debugger those objects are finalized and gone. */
Index: glibc-fsf-trunk-quilt/elf/dl-iteratephdr.c
===================================================================
--- glibc-fsf-trunk-quilt.orig/elf/dl-iteratephdr.c 2014-01-29 11:23:16.000000000 +0000
+++ glibc-fsf-trunk-quilt/elf/dl-iteratephdr.c 2014-01-29 12:09:13.062013406 +0000
@@ -86,34 +86,4 @@ __dl_iterate_phdr (int (*callback) (stru
}
hidden_def (__dl_iterate_phdr)
-#ifdef SHARED
-
weak_alias (__dl_iterate_phdr, dl_iterate_phdr);
-
-#else
-
-int
-dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
- size_t size, void *data), void *data)
-{
- if (_dl_phnum != 0)
- {
- /* This entry describes this statically-linked program itself. */
- struct dl_phdr_info info;
- int ret;
- info.dlpi_addr = 0;
- info.dlpi_name = "";
- info.dlpi_phdr = _dl_phdr;
- info.dlpi_phnum = _dl_phnum;
- info.dlpi_adds = GL(dl_load_adds);
- info.dlpi_subs = GL(dl_load_adds) - GL(dl_ns)[LM_ID_BASE]._ns_nloaded;
- ret = (*callback) (&info, sizeof (struct dl_phdr_info), data);
- if (ret)
- return ret;
- }
-
- return __dl_iterate_phdr (callback, data);
-}
-
-
-#endif
Index: glibc-fsf-trunk-quilt/elf/dl-load.c
===================================================================
--- glibc-fsf-trunk-quilt.orig/elf/dl-load.c 2014-01-29 11:23:16.000000000 +0000
+++ glibc-fsf-trunk-quilt/elf/dl-load.c 2014-01-29 12:09:13.062013406 +0000
@@ -2233,23 +2233,17 @@ _dl_map_object (struct link_map *loader,
if (cached != NULL)
{
-# ifdef SHARED
// XXX Correct to unconditionally default to namespace 0?
l = (loader
?: GL(dl_ns)[LM_ID_BASE]._ns_loaded
- ?: &GL(dl_rtld_map));
-# else
- l = loader;
+# ifdef SHARED
+ ?: &GL(dl_rtld_map)
# endif
+ );
/* If the loader has the DF_1_NODEFLIB flag set we must not
use a cache entry from any of these directories. */
- if (
-# ifndef SHARED
- /* 'l' is always != NULL for dynamically linked objects. */
- l != NULL &&
-# endif
- __builtin_expect (l->l_flags_1 & DF_1_NODEFLIB, 0))
+ if (__builtin_expect (l->l_flags_1 & DF_1_NODEFLIB, 0))
{
const char *dirp = system_dirs;
unsigned int cnt = 0;
Index: glibc-fsf-trunk-quilt/elf/dl-support.c
===================================================================
--- glibc-fsf-trunk-quilt.orig/elf/dl-support.c 2014-01-29 11:23:16.000000000 +0000
+++ glibc-fsf-trunk-quilt/elf/dl-support.c 2014-01-29 12:12:22.092011006 +0000
@@ -91,6 +91,7 @@ static struct link_map _dl_main_map =
.l_scope = _dl_main_map.l_scope_mem,
.l_local_scope = { &_dl_main_map.l_searchlist },
.l_used = 1,
+ .l_flags_1 = DF_1_NODEFLIB,
.l_tls_offset = NO_TLS_OFFSET,
.l_serial = 1,
};
@@ -311,6 +312,8 @@ internal_function
_dl_non_dynamic_init (void)
{
_dl_main_map.l_origin = _dl_get_origin ();
+ _dl_main_map.l_phdr = GL(dl_phdr);
+ _dl_main_map.l_phnum = GL(dl_phnum);
if (HP_TIMING_AVAIL)
HP_TIMING_NOW (_dl_cpuclock_offset);