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glibc/glibc-rh1817513-74.patch

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commit 17796419b5fd694348cceb65c3f77601faae082c
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Tue Jul 7 10:49:11 2020 +0100
rtld: Account static TLS surplus for audit modules
The new static TLS surplus size computation is
surplus_tls = 192 * (nns-1) + 144 * nns + 512
where nns is controlled via the rtld.nns tunable. This commit
accounts audit modules too so nns = rtld.nns + audit modules.
rtld.nns should only include the namespaces required by the
application, namespaces for audit modules are accounted on top
of that so audit modules don't use up the static TLS that is
reserved for the application. This allows loading many audit
modules without tuning rtld.nns or using up static TLS, and it
fixes
FAIL: elf/tst-auditmany
Note that DL_NNS is currently a hard upper limit for nns, and
if rtld.nns + audit modules go over the limit that's a fatal
error. By default rtld.nns is 4 which allows 12 audit modules.
Counting the audit modules is based on existing audit string
parsing code, we cannot use GLRO(dl_naudit) before the modules
are actually loaded.
Conflicts:
elf/rtld.c
(Caused by glibc-fedora-__libc_multiple_libcs.patch.)
diff --git a/csu/libc-tls.c b/csu/libc-tls.c
index 08ed2b988b58ac6c..6f2a47dc86222407 100644
--- a/csu/libc-tls.c
+++ b/csu/libc-tls.c
@@ -132,8 +132,8 @@ __libc_setup_tls (void)
break;
}
- /* Calculate the size of the static TLS surplus. */
- _dl_tls_static_surplus_init ();
+ /* Calculate the size of the static TLS surplus, with 0 auditors. */
+ _dl_tls_static_surplus_init (0);
/* We have to set up the TCB block which also (possibly) contains
'errno'. Therefore we avoid 'malloc' which might touch 'errno'.
diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index ef57a21391bb36fa..cfda76f6de96df57 100644
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -49,7 +49,10 @@
that affects the size of the static TLS and by default it's small enough
not to cause problems with existing applications. The limit is not
enforced or checked: it is the user's responsibility to increase rtld.nns
- if more dlmopen namespaces are used. */
+ if more dlmopen namespaces are used.
+
+ Audit modules use their own namespaces, they are not included in rtld.nns,
+ but come on top when computing the number of namespaces. */
/* Size of initial-exec TLS in libc.so. */
#define LIBC_IE_TLS 192
@@ -60,8 +63,11 @@
/* Size of additional surplus TLS, placeholder for TLS optimizations. */
#define OPT_SURPLUS_TLS 512
+/* Calculate the size of the static TLS surplus, when the given
+ number of audit modules are loaded. Must be called after the
+ number of audit modules is known and before static TLS allocation. */
void
-_dl_tls_static_surplus_init (void)
+_dl_tls_static_surplus_init (size_t naudit)
{
size_t nns;
@@ -73,6 +79,11 @@ _dl_tls_static_surplus_init (void)
#endif
if (nns > DL_NNS)
nns = DL_NNS;
+ if (DL_NNS - nns < naudit)
+ _dl_fatal_printf ("Failed loading %lu audit modules, %lu are supported.\n",
+ (unsigned long) naudit, (unsigned long) (DL_NNS - nns));
+ nns += naudit;
+
GLRO(dl_tls_static_surplus) = ((nns - 1) * LIBC_IE_TLS
+ nns * OTHER_IE_TLS
+ OPT_SURPLUS_TLS);
diff --git a/elf/rtld.c b/elf/rtld.c
index a440741f4c1b3c91..67441ac6f252350e 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -297,6 +297,23 @@ audit_list_next (struct audit_list *list)
}
}
+/* Count audit modules before they are loaded so GLRO(dl_naudit)
+ is not yet usable. */
+static size_t
+audit_list_count (struct audit_list *list)
+{
+ /* Restore the audit_list iterator state at the end. */
+ const char *saved_tail = list->current_tail;
+ size_t naudit = 0;
+
+ assert (list->current_index == 0);
+ while (audit_list_next (list) != NULL)
+ naudit++;
+ list->current_tail = saved_tail;
+ list->current_index = 0;
+ return naudit;
+}
+
/* Set nonzero during loading and initialization of executable and
libraries, cleared before the executable's entry point runs. This
must not be initialized to nonzero, because the unused dynamic
@@ -734,7 +751,7 @@ match_version (const char *string, struct link_map *map)
static bool tls_init_tp_called;
static void *
-init_tls (void)
+init_tls (size_t naudit)
{
/* Number of elements in the static TLS block. */
GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
@@ -777,7 +794,7 @@ init_tls (void)
assert (i == GL(dl_tls_max_dtv_idx));
/* Calculate the size of the static TLS surplus. */
- _dl_tls_static_surplus_init ();
+ _dl_tls_static_surplus_init (naudit);
/* Compute the TLS offsets for the various blocks. */
_dl_determine_tlsoffset ();
@@ -1659,9 +1676,11 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
bool need_security_init = true;
if (audit_list.length > 0)
{
+ size_t naudit = audit_list_count (&audit_list);
+
/* Since we start using the auditing DSOs right away we need to
initialize the data structures now. */
- tcbp = init_tls ();
+ tcbp = init_tls (naudit);
/* Initialize security features. We need to do it this early
since otherwise the constructors of the audit libraries will
@@ -1671,6 +1690,10 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
need_security_init = false;
load_audit_modules (main_map, &audit_list);
+
+ /* The count based on audit strings may overestimate the number
+ of audit modules that got loaded, but not underestimate. */
+ assert (GLRO(dl_naudit) <= naudit);
}
/* Keep track of the currently loaded modules to count how many
@@ -1914,7 +1937,7 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
multiple threads (from a non-TLS-using libpthread). */
bool was_tls_init_tp_called = tls_init_tp_called;
if (tcbp == NULL)
- tcbp = init_tls ();
+ tcbp = init_tls (0);
if (__glibc_likely (need_security_init))
/* Initialize security features. But only if we have not done it
diff --git a/manual/tunables.texi b/manual/tunables.texi
index e092b8e81a18d739..e6a3e9a2cf5c959c 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -241,9 +241,12 @@ Sets the number of supported dynamic link namespaces (see @code{dlmopen}).
Currently this limit can be set between 1 and 16 inclusive, the default is 4.
Each link namespace consumes some memory in all thread, and thus raising the
limit will increase the amount of memory each thread uses. Raising the limit
-is useful when your application uses more than 4 dynamic linker audit modules
-e.g. @env{LD_AUDIT}, or will use more than 4 dynamic link namespaces as created
-by @code{dlmopen} with an lmid argument of @code{LM_ID_NEWLM}.
+is useful when your application uses more than 4 dynamic link namespaces as
+created by @code{dlmopen} with an lmid argument of @code{LM_ID_NEWLM}.
+Dynamic linker audit modules are loaded in their own dynamic link namespaces,
+but they are not accounted for in @code{glibc.rtld.nns}. They implicitly
+increase the per-thread memory usage as necessary, so this tunable does
+not need to be changed to allow many audit modules e.g. via @env{LD_AUDIT}.
@end deftp
@node Elision Tunables
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index e54105848c3cb7d1..293f3ab5a496afdf 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -1104,8 +1104,9 @@ extern size_t _dl_count_modids (void) attribute_hidden;
/* Calculate offset of the TLS blocks in the static TLS block. */
extern void _dl_determine_tlsoffset (void) attribute_hidden;
-/* Calculate the size of the static TLS surplus. */
-void _dl_tls_static_surplus_init (void) attribute_hidden;
+/* Calculate the size of the static TLS surplus, when the given
+ number of audit modules are loaded. */
+void _dl_tls_static_surplus_init (size_t naudit) attribute_hidden;
#ifndef SHARED
/* Set up the TCB for statically linked applications. This is called
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