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233 lines
8.8 KiB
233 lines
8.8 KiB
commit d0f07f7df8d9758c838674b70144ac73bcbd1634 |
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Author: Florian Weimer <fweimer@redhat.com> |
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Date: Tue May 30 13:25:50 2023 +0200 |
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elf: Make more functions available for binding during dlclose (bug 30425) |
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Previously, after destructors for a DSO have been invoked, ld.so refused |
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to bind against that DSO in all cases. Relax this restriction somewhat |
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if the referencing object is itself a DSO that is being unloaded. This |
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assumes that the symbol reference is not going to be stored anywhere. |
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The situation in the test case can arise fairly easily with C++ and |
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objects that are built with different optimization levels and therefore |
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define different functions with vague linkage. |
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Reviewed-by: Carlos O'Donell <carlos@redhat.com> |
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Conflicts: |
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elf/Makefile |
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(Test conflicts resolved by hand) |
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diff --git a/elf/Makefile b/elf/Makefile |
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index 0daa8a85ec1a1bc5..8e1f91bcd917fd4e 100644 |
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--- a/elf/Makefile |
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+++ b/elf/Makefile |
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@@ -392,6 +392,7 @@ tests += \ |
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tst-debug1 \ |
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tst-deep1 \ |
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tst-dl-is_dso \ |
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+ tst-dlclose-lazy \ |
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tst-dlmodcount \ |
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tst-dlmopen1 \ |
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tst-dlmopen3 \ |
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@@ -742,6 +743,8 @@ modules-names = \ |
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tst-deep1mod2 \ |
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tst-deep1mod3 \ |
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tst-dlmopen1mod \ |
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+ tst-dlclose-lazy-mod1 \ |
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+ tst-dlclose-lazy-mod2 \ |
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tst-dlmopen-dlerror-mod \ |
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tst-dlmopen-gethostbyname-mod \ |
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tst-dlmopen-twice-mod1 \ |
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@@ -2676,3 +2679,8 @@ tst-audit-tlsdesc-dlopen-ENV = LD_AUDIT=$(objpfx)tst-auditmod-tlsdesc.so |
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$(objpfx)tst-dlmopen-twice.out: \ |
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$(objpfx)tst-dlmopen-twice-mod1.so \ |
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$(objpfx)tst-dlmopen-twice-mod2.so |
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+ |
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+LDFLAGS-tst-dlclose-lazy-mod1.so = -Wl,-z,lazy,--no-as-needed |
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+$(objpfx)tst-dlclose-lazy-mod1.so: $(objpfx)tst-dlclose-lazy-mod2.so |
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+$(objpfx)tst-dlclose-lazy.out: \ |
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+ $(objpfx)tst-dlclose-lazy-mod1.so $(objpfx)tst-dlclose-lazy-mod2.so |
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diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c |
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index 3391a990c8d288e5..94ae2d0c46696118 100644 |
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--- a/elf/dl-lookup.c |
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+++ b/elf/dl-lookup.c |
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@@ -380,8 +380,25 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash, |
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if ((type_class & ELF_RTYPE_CLASS_COPY) && map->l_type == lt_executable) |
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continue; |
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- /* Do not look into objects which are going to be removed. */ |
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- if (map->l_removed) |
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+ /* Do not look into objects which are going to be removed, |
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+ except when the referencing object itself is being removed. |
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+ |
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+ The second part covers the situation when an object lazily |
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+ binds to another object while running its destructor, but the |
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+ destructor of the other object has already run, so that |
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+ dlclose has set l_removed. It may not always be obvious how |
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+ to avoid such a scenario to programmers creating DSOs, |
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+ particularly if C++ vague linkage is involved and triggers |
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+ symbol interposition. |
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+ |
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+ Accepting these to-be-removed objects makes the lazy and |
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+ BIND_NOW cases more similar. (With BIND_NOW, the symbol is |
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+ resolved early, before the destructor call, so the issue does |
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+ not arise.). Behavior matches the constructor scenario: the |
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+ implementation allows binding to symbols of objects whose |
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+ constructors have not run. In fact, not doing this would be |
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+ mostly incompatible with symbol interposition. */ |
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+ if (map->l_removed && !(undef_map != NULL && undef_map->l_removed)) |
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continue; |
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/* Print some debugging info if wanted. */ |
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diff --git a/elf/tst-dlclose-lazy-mod1.c b/elf/tst-dlclose-lazy-mod1.c |
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new file mode 100644 |
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index 0000000000000000..8439dc1925cc8b41 |
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--- /dev/null |
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+++ b/elf/tst-dlclose-lazy-mod1.c |
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@@ -0,0 +1,36 @@ |
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+/* Lazy binding during dlclose. Directly loaded module. |
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+ Copyright (C) 2023 Free Software Foundation, Inc. |
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+ This file is part of the GNU C Library. |
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+ |
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+ The GNU C Library is free software; you can redistribute it and/or |
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+ modify it under the terms of the GNU Lesser General Public |
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+ License as published by the Free Software Foundation; either |
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+ version 2.1 of the License, or (at your option) any later version. |
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+ |
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+ The GNU C Library is distributed in the hope that it will be useful, |
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of |
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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+ Lesser General Public License for more details. |
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+ |
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+ You should have received a copy of the GNU Lesser General Public |
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+ License along with the GNU C Library; if not, see |
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+ <https://www.gnu.org/licenses/>. */ |
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+ |
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+/* This function is called from exported_function below. It is only |
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+ defined in this module. The weak attribute mimics how G++ |
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+ implements vague linkage for C++. */ |
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+void __attribute__ ((weak)) |
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+lazily_bound_exported_function (void) |
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+{ |
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+} |
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+ |
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+/* Called from tst-dlclose-lazy-mod2.so. */ |
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+void |
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+exported_function (int call_it) |
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+{ |
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+ if (call_it) |
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+ /* Previous to the fix this would crash when called during dlclose |
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+ since symbols from the DSO were no longer available for binding |
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+ (bug 30425) after the DSO started being closed by dlclose. */ |
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+ lazily_bound_exported_function (); |
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+} |
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diff --git a/elf/tst-dlclose-lazy-mod2.c b/elf/tst-dlclose-lazy-mod2.c |
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new file mode 100644 |
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index 0000000000000000..767f69ffdb23a685 |
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--- /dev/null |
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+++ b/elf/tst-dlclose-lazy-mod2.c |
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@@ -0,0 +1,49 @@ |
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+/* Lazy binding during dlclose. Indirectly loaded module. |
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+ Copyright (C) 2023 Free Software Foundation, Inc. |
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+ This file is part of the GNU C Library. |
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+ |
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+ The GNU C Library is free software; you can redistribute it and/or |
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+ modify it under the terms of the GNU Lesser General Public |
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+ License as published by the Free Software Foundation; either |
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+ version 2.1 of the License, or (at your option) any later version. |
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+ |
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+ The GNU C Library is distributed in the hope that it will be useful, |
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of |
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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+ Lesser General Public License for more details. |
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+ |
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+ You should have received a copy of the GNU Lesser General Public |
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+ License along with the GNU C Library; if not, see |
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+ <https://www.gnu.org/licenses/>. */ |
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+ |
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+#include <stdio.h> |
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+#include <stdlib.h> |
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+ |
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+void |
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+exported_function (int ignored) |
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+{ |
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+ /* This function is interposed from tst-dlclose-lazy-mod1.so and |
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+ thus never called. */ |
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+ abort (); |
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+} |
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+ |
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+static void __attribute__ ((constructor)) |
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+init (void) |
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+{ |
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+ puts ("info: tst-dlclose-lazy-mod2.so constructor called"); |
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+ |
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+ /* Trigger lazy binding to the definition in |
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+ tst-dlclose-lazy-mod1.so, but not for |
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+ lazily_bound_exported_function in that module. */ |
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+ exported_function (0); |
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+} |
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+ |
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+static void __attribute__ ((destructor)) |
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+fini (void) |
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+{ |
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+ puts ("info: tst-dlclose-lazy-mod2.so destructor called"); |
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+ |
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+ /* Trigger the lazily_bound_exported_function call in |
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+ exported_function in tst-dlclose-lazy-mod1.so. */ |
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+ exported_function (1); |
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+} |
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diff --git a/elf/tst-dlclose-lazy.c b/elf/tst-dlclose-lazy.c |
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new file mode 100644 |
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index 0000000000000000..976a6bb6f64fa981 |
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--- /dev/null |
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+++ b/elf/tst-dlclose-lazy.c |
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@@ -0,0 +1,47 @@ |
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+/* Test lazy binding during dlclose (bug 30425). |
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+ Copyright (C) 2023 Free Software Foundation, Inc. |
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+ This file is part of the GNU C Library. |
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+ |
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+ The GNU C Library is free software; you can redistribute it and/or |
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+ modify it under the terms of the GNU Lesser General Public |
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+ License as published by the Free Software Foundation; either |
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+ version 2.1 of the License, or (at your option) any later version. |
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+ |
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+ The GNU C Library is distributed in the hope that it will be useful, |
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of |
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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+ Lesser General Public License for more details. |
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+ |
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+ You should have received a copy of the GNU Lesser General Public |
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+ License along with the GNU C Library; if not, see |
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+ <https://www.gnu.org/licenses/>. */ |
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+ |
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+/* This test re-creates a situation that can arise naturally for C++ |
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+ applications due to the use of vague linkage and differences in the |
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+ set of compiler-emitted functions. A function in |
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+ tst-dlclose-lazy-mod1.so (exported_function) interposes a function |
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+ in tst-dlclose-lazy-mod2.so. This function is called from the |
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+ destructor in tst-dlclose-lazy-mod2.so, after the destructor for |
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+ tst-dlclose-lazy-mod1.so has already completed. Prior to the fix |
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+ for bug 30425, this would lead to a lazy binding failure in |
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+ tst-dlclose-lazy-mod1.so because dlclose had already marked the DSO |
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+ as unavailable for binding (by setting l_removed). */ |
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+ |
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+#include <dlfcn.h> |
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+#include <support/xdlfcn.h> |
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+#include <support/check.h> |
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+ |
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+int |
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+main (void) |
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+{ |
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+ /* Load tst-dlclose-lazy-mod1.so, indirectly loading |
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+ tst-dlclose-lazy-mod2.so. */ |
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+ void *handle = xdlopen ("tst-dlclose-lazy-mod1.so", RTLD_GLOBAL | RTLD_LAZY); |
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+ |
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+ /* Invoke the destructor of tst-dlclose-lazy-mod2.so, which calls |
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+ into tst-dlclose-lazy-mod1.so after its destructor has been |
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+ called. */ |
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+ xdlclose (handle); |
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+ |
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+ return 0; |
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+}
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