commit 91c2e6c3db44297bf4cb3a2e3c40236c5b6a0b23
Author: Florian Weimer <fweimer@redhat.com>
Date: Fri Apr 29 17:00:53 2022 +0200
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>
(cherry picked from commit d056c212130280c0a54d9a4f72170ec621b70ce5)
diff --git a/dlfcn/Makefile b/dlfcn/Makefile
index 6bbfbb8344da05cb..d3965427dabed898 100644
--- a/dlfcn/Makefile
+++ b/dlfcn/Makefile
@@ -73,6 +73,10 @@ tststatic3-ENV = $(tststatic-ENV)
tststatic4-ENV = $(tststatic-ENV)
tststatic5-ENV = $(tststatic-ENV)
+tests-internal += \
+ tst-dlinfo-phdr \
+ # tests-internal
+
ifneq (,$(CXX))
modules-names += bug-atexit3-lib
else
diff --git a/dlfcn/dlfcn.h b/dlfcn/dlfcn.h
index 4a3b870a487ea789..24388cfedae4dd67 100644
--- a/dlfcn/dlfcn.h
+++ b/dlfcn/dlfcn.h
@@ -162,7 +162,12 @@ enum
segment, or if the calling thread has not allocated a block for it. */
RTLD_DI_TLS_DATA = 10,
- RTLD_DI_MAX = 10
+ /* Treat ARG as const ElfW(Phdr) **, and store the address of the
+ program header array at that location. The dlinfo call returns
+ the number of program headers in the array. */
+ RTLD_DI_PHDR = 11,
+
+ RTLD_DI_MAX = 11
};
diff --git a/dlfcn/dlinfo.c b/dlfcn/dlinfo.c
index 47d2daa96fa5986f..1842925fb7c594dd 100644
--- a/dlfcn/dlinfo.c
+++ b/dlfcn/dlinfo.c
@@ -28,6 +28,10 @@ struct dlinfo_args
void *handle;
int request;
void *arg;
+
+ /* This is the value that is returned from dlinfo if no error is
+ signaled. */
+ int result;
};
static void
@@ -40,6 +44,7 @@ dlinfo_doit (void *argsblock)
{
case RTLD_DI_CONFIGADDR:
default:
+ args->result = -1;
_dl_signal_error (0, NULL, NULL, N_("unsupported dlinfo request"));
break;
@@ -75,6 +80,11 @@ dlinfo_doit (void *argsblock)
*(void **) args->arg = data;
break;
}
+
+ case RTLD_DI_PHDR:
+ *(const ElfW(Phdr) **) args->arg = l->l_phdr;
+ args->result = l->l_phnum;
+ break;
}
}
@@ -82,7 +92,8 @@ static int
dlinfo_implementation (void *handle, int request, void *arg)
{
struct dlinfo_args args = { handle, request, arg };
- return _dlerror_run (&dlinfo_doit, &args) ? -1 : 0;
+ _dlerror_run (&dlinfo_doit, &args);
+ return args.result;
}
#ifdef SHARED
diff --git a/dlfcn/tst-dlinfo-phdr.c b/dlfcn/tst-dlinfo-phdr.c
new file mode 100644
index 0000000000000000..a15a7d48ebd3b976
--- /dev/null
+++ b/dlfcn/tst-dlinfo-phdr.c
@@ -0,0 +1,125 @@
+/* Test for dlinfo (RTLD_DI_PHDR).
+ Copyright (C) 2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <dlfcn.h>
+#include <link.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/auxv.h>
+
+#include <support/check.h>
+#include <support/xdlfcn.h>
+
+/* Used to verify that the program header array appears as expected
+ among the dl_iterate_phdr callback invocations. */
+
+struct dlip_callback_args
+{
+ struct link_map *l; /* l->l_addr is used to find the object. */
+ const ElfW(Phdr) *phdr; /* Expected program header pointed. */
+ int phnum; /* Expected program header count. */
+ bool found; /* True if l->l_addr has been found. */
+};
+
+static int
+dlip_callback (struct dl_phdr_info *dlpi, size_t size, void *closure)
+{
+ TEST_COMPARE (sizeof (*dlpi), size);
+ struct dlip_callback_args *args = closure;
+
+ if (dlpi->dlpi_addr == args->l->l_addr)
+ {
+ TEST_VERIFY (!args->found);
+ args->found = true;
+ TEST_VERIFY (args->phdr == dlpi->dlpi_phdr);
+ TEST_COMPARE (args->phnum, dlpi->dlpi_phnum);
+ }
+
+ return 0;
+}
+
+static int
+do_test (void)
+{
+ /* Avoid a copy relocation. */
+ struct r_debug *debug = xdlsym (RTLD_DEFAULT, "_r_debug");
+ struct link_map *l = (struct link_map *) debug->r_map;
+ TEST_VERIFY_EXIT (l != NULL);
+
+ do
+ {
+ printf ("info: checking link map %p (%p) for \"%s\"\n",
+ l, l->l_phdr, l->l_name);
+
+ /* Cause dlerror () to return an error message. */
+ dlsym (RTLD_DEFAULT, "does-not-exist");
+
+ /* Use the extension that link maps are valid dlopen handles. */
+ const ElfW(Phdr) *phdr;
+ int phnum = dlinfo (l, RTLD_DI_PHDR, &phdr);
+ TEST_VERIFY (phnum >= 0);
+ /* Verify that the error message has been cleared. */
+ TEST_COMPARE_STRING (dlerror (), NULL);
+
+ TEST_VERIFY (phdr == l->l_phdr);
+ TEST_COMPARE (phnum, l->l_phnum);
+
+ /* Check that we can find PT_DYNAMIC among the array. */
+ {
+ bool dynamic_found = false;
+ for (int i = 0; i < phnum; ++i)
+ if (phdr[i].p_type == PT_DYNAMIC)
+ {
+ dynamic_found = true;
+ TEST_COMPARE ((ElfW(Addr)) l->l_ld, l->l_addr + phdr[i].p_vaddr);
+ }
+ TEST_VERIFY (dynamic_found);
+ }
+
+ /* Check that dl_iterate_phdr finds the link map with the same
+ program headers. */
+ {
+ struct dlip_callback_args args =
+ {
+ .l = l,
+ .phdr = phdr,
+ .phnum = phnum,
+ .found = false,
+ };
+ TEST_COMPARE (dl_iterate_phdr (dlip_callback, &args), 0);
+ TEST_VERIFY (args.found);
+ }
+
+ if (l->l_prev == NULL)
+ {
+ /* This is the executable, so the information is also
+ available via getauxval. */
+ TEST_COMPARE_STRING (l->l_name, "");
+ TEST_VERIFY (phdr == (const ElfW(Phdr) *) getauxval (AT_PHDR));
+ TEST_COMPARE (phnum, getauxval (AT_PHNUM));
+ }
+
+ l = l->l_next;
+ }
+ while (l != NULL);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/manual/dynlink.texi b/manual/dynlink.texi
index dbf3de11769d8e57..7dcac64889e389fd 100644
--- a/manual/dynlink.texi
+++ b/manual/dynlink.texi
@@ -30,9 +30,9 @@ location @var{arg}, based on @var{request}. The @var{handle} argument
must be a pointer returned by @code{dlopen} or @code{dlmopen}; it must
not have been closed by @code{dlclose}.
-On success, @code{dlinfo} returns 0. If there is an error, the function
-returns @math{-1}, and @code{dlerror} can be used to obtain a
-corresponding error message.
+On success, @code{dlinfo} returns 0 for most request types; exceptions
+are noted below. If there is an error, the function returns @math{-1},
+and @code{dlerror} can be used to obtain a corresponding error message.
The following operations are defined for use with @var{request}:
@@ -84,6 +84,15 @@ This request writes the TLS module ID for the shared object @var{handle}
to @code{*@var{arg}}. The argument @var{arg} must be the address of an
object of type @code{size_t}. The module ID is zero if the object
does not have an associated TLS block.
+
+@item RTLD_DI_PHDR
+This request writes the address of the program header array to
+@code{*@var{arg}}. The argument @var{arg} must be the address of an
+object of type @code{const ElfW(Phdr) *} (that is,
+@code{const Elf32_Phdr *} or @code{const Elf64_Phdr *}, as appropriate
+for the current architecture). For this request, the value returned by
+@code{dlinfo} is the number of program headers in the program header
+array.
@end vtable
The @code{dlinfo} function is a GNU extension.