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dlfcn: Implement the RTLD_DI_PHDR request type for dlinfo
The information is theoretically available via dl_iterate_phdr as well, but that approach is very slow if there are many shared objects. Reviewed-by: Carlos O'Donell <carlos@redhat.com> Tested-by: Carlos O'Donell <carlos@rehdat.com>
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@ -73,6 +73,10 @@ tststatic3-ENV = $(tststatic-ENV)
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tststatic4-ENV = $(tststatic-ENV)
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tststatic5-ENV = $(tststatic-ENV)
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tests-internal += \
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tst-dlinfo-phdr \
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# tests-internal
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ifneq (,$(CXX))
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modules-names += bug-atexit3-lib
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else
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@ -164,7 +164,12 @@ enum
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segment, or if the calling thread has not allocated a block for it. */
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RTLD_DI_TLS_DATA = 10,
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RTLD_DI_MAX = 10
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/* Treat ARG as const ElfW(Phdr) **, and store the address of the
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program header array at that location. The dlinfo call returns
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the number of program headers in the array. */
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RTLD_DI_PHDR = 11,
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RTLD_DI_MAX = 11
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};
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@ -28,6 +28,10 @@ struct dlinfo_args
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void *handle;
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int request;
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void *arg;
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/* This is the value that is returned from dlinfo if no error is
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signaled. */
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int result;
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};
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static void
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@ -40,6 +44,7 @@ dlinfo_doit (void *argsblock)
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{
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case RTLD_DI_CONFIGADDR:
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default:
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args->result = -1;
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_dl_signal_error (0, NULL, NULL, N_("unsupported dlinfo request"));
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break;
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@ -75,6 +80,11 @@ dlinfo_doit (void *argsblock)
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*(void **) args->arg = data;
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break;
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}
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case RTLD_DI_PHDR:
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*(const ElfW(Phdr) **) args->arg = l->l_phdr;
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args->result = l->l_phnum;
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break;
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}
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}
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@ -82,7 +92,8 @@ static int
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dlinfo_implementation (void *handle, int request, void *arg)
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{
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struct dlinfo_args args = { handle, request, arg };
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return _dlerror_run (&dlinfo_doit, &args) ? -1 : 0;
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_dlerror_run (&dlinfo_doit, &args);
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return args.result;
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}
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#ifdef SHARED
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125
dlfcn/tst-dlinfo-phdr.c
Normal file
125
dlfcn/tst-dlinfo-phdr.c
Normal file
@ -0,0 +1,125 @@
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/* Test for dlinfo (RTLD_DI_PHDR).
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Copyright (C) 2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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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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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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#include <dlfcn.h>
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#include <link.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/auxv.h>
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#include <support/check.h>
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#include <support/xdlfcn.h>
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/* Used to verify that the program header array appears as expected
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among the dl_iterate_phdr callback invocations. */
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struct dlip_callback_args
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{
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struct link_map *l; /* l->l_addr is used to find the object. */
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const ElfW(Phdr) *phdr; /* Expected program header pointed. */
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int phnum; /* Expected program header count. */
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bool found; /* True if l->l_addr has been found. */
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};
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static int
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dlip_callback (struct dl_phdr_info *dlpi, size_t size, void *closure)
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{
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TEST_COMPARE (sizeof (*dlpi), size);
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struct dlip_callback_args *args = closure;
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if (dlpi->dlpi_addr == args->l->l_addr)
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{
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TEST_VERIFY (!args->found);
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args->found = true;
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TEST_VERIFY (args->phdr == dlpi->dlpi_phdr);
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TEST_COMPARE (args->phnum, dlpi->dlpi_phnum);
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}
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return 0;
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}
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static int
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do_test (void)
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{
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/* Avoid a copy relocation. */
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struct r_debug *debug = xdlsym (RTLD_DEFAULT, "_r_debug");
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struct link_map *l = (struct link_map *) debug->r_map;
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TEST_VERIFY_EXIT (l != NULL);
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do
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{
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printf ("info: checking link map %p (%p) for \"%s\"\n",
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l, l->l_phdr, l->l_name);
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/* Cause dlerror () to return an error message. */
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dlsym (RTLD_DEFAULT, "does-not-exist");
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/* Use the extension that link maps are valid dlopen handles. */
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const ElfW(Phdr) *phdr;
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int phnum = dlinfo (l, RTLD_DI_PHDR, &phdr);
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TEST_VERIFY (phnum >= 0);
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/* Verify that the error message has been cleared. */
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TEST_COMPARE_STRING (dlerror (), NULL);
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TEST_VERIFY (phdr == l->l_phdr);
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TEST_COMPARE (phnum, l->l_phnum);
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/* Check that we can find PT_DYNAMIC among the array. */
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{
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bool dynamic_found = false;
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for (int i = 0; i < phnum; ++i)
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if (phdr[i].p_type == PT_DYNAMIC)
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{
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dynamic_found = true;
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TEST_COMPARE ((ElfW(Addr)) l->l_ld, l->l_addr + phdr[i].p_vaddr);
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}
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TEST_VERIFY (dynamic_found);
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}
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/* Check that dl_iterate_phdr finds the link map with the same
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program headers. */
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{
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struct dlip_callback_args args =
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{
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.l = l,
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.phdr = phdr,
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.phnum = phnum,
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.found = false,
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};
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TEST_COMPARE (dl_iterate_phdr (dlip_callback, &args), 0);
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TEST_VERIFY (args.found);
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}
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if (l->l_prev == NULL)
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{
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/* This is the executable, so the information is also
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available via getauxval. */
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TEST_COMPARE_STRING (l->l_name, "");
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TEST_VERIFY (phdr == (const ElfW(Phdr) *) getauxval (AT_PHDR));
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TEST_COMPARE (phnum, getauxval (AT_PHNUM));
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}
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l = l->l_next;
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}
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while (l != NULL);
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return 0;
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}
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#include <support/test-driver.c>
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@ -30,9 +30,9 @@ location @var{arg}, based on @var{request}. The @var{handle} argument
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must be a pointer returned by @code{dlopen} or @code{dlmopen}; it must
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not have been closed by @code{dlclose}.
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On success, @code{dlinfo} returns 0. If there is an error, the function
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returns @math{-1}, and @code{dlerror} can be used to obtain a
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corresponding error message.
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On success, @code{dlinfo} returns 0 for most request types; exceptions
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are noted below. If there is an error, the function returns @math{-1},
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and @code{dlerror} can be used to obtain a corresponding error message.
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The following operations are defined for use with @var{request}:
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@ -84,6 +84,15 @@ This request writes the TLS module ID for the shared object @var{handle}
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to @code{*@var{arg}}. The argument @var{arg} must be the address of an
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object of type @code{size_t}. The module ID is zero if the object
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does not have an associated TLS block.
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@item RTLD_DI_PHDR
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This request writes the address of the program header array to
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@code{*@var{arg}}. The argument @var{arg} must be the address of an
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object of type @code{const ElfW(Phdr) *} (that is,
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@code{const Elf32_Phdr *} or @code{const Elf64_Phdr *}, as appropriate
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for the current architecture). For this request, the value returned by
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@code{dlinfo} is the number of program headers in the program header
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array.
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@end vtable
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The @code{dlinfo} function is a GNU extension.
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