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29476485f9
check_gcs is called for each dependency of a DSO, but the GNU property of the ld.so is not processed so ldso->l_mach.gcs may not be correct. Just assume ld.so is GCS compatible independently of the ELF marking. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
122 lines
3.7 KiB
C
122 lines
3.7 KiB
C
/* AArch64 GCS functions.
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Copyright (C) 2024-2025 Free Software Foundation, Inc.
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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 <unistd.h>
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#include <ldsodefs.h>
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/* GCS is disabled. */
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#define GCS_POLICY_DISABLED 0
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/* Enable GCS, abort if unmarked binary is found. */
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#define GCS_POLICY_ENFORCED 1
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/* Optionally enable GCS if all startup dependencies are marked. */
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#define GCS_POLICY_OPTIONAL 2
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/* Override binary marking and always enabled GCS. */
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#define GCS_POLICY_OVERRIDE 3
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static void
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fail (struct link_map *l, const char *program)
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{
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if (program && program[0])
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_dl_fatal_printf ("%s: %s: %s\n", program, l->l_name, "not GCS compatible");
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else if (program)
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_dl_fatal_printf ("%s\n", "not GCS compatible");
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else
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_dl_signal_error (0, l->l_name, "dlopen", "not GCS compatible");
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}
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static void
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unsupported (void)
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{
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_dl_fatal_printf ("%s\n", "unsupported GCS policy");
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}
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/* This function is called only when binary markings are not
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ignored and GCS is supposed to be enabled. This occurs
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for the GCS_POLICY_ENFORCED and GCS_POLICY_ENFORCED policies. */
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static bool
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check_gcs (struct link_map *l, const char *program, bool enforced)
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{
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#ifdef SHARED
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/* Ignore GCS marking on ld.so: its properties are not processed. */
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if (is_rtld_link_map (l->l_real))
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return true;
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#endif
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/* Binary is marked, all good. */
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if (l->l_mach.gcs)
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return true;
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/* Binary is not marked and loaded via dlopen: abort. */
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if (program == NULL)
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fail (l, program);
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/* Binary is not marked and we enforce GCS: abort. */
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if (enforced)
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fail (l, program);
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/* Binary is not marked but GSC is optional: disable GCS. */
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else
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{
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GL(dl_aarch64_gcs) = 0;
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return false;
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}
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__builtin_unreachable ();
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}
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/* Iterate over all dependencies and check GCS marking.
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This function is called only when binary markings are not
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ignored and GCS is supposed to be enabled. This occurs
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for the GCS_POLICY_ENFORCED and GCS_POLICY_ENFORCED policies.
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We interrupt checking if GCS is optional and we already know
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it is going to be disabled. */
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static void
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check_gcs_depends (struct link_map *l, const char *program, bool enforced)
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{
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if (check_gcs (l, program, enforced))
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for (unsigned int i = 0; i < l->l_searchlist.r_nlist; i++)
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if (!check_gcs (l->l_searchlist.r_list[i], program, enforced))
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break;
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}
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/* Apply GCS policy for L and its dependencies.
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PROGRAM is NULL when this check is invoked for dl_open. */
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void
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_dl_gcs_check (struct link_map *l, const char *program)
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{
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unsigned long policy = GL (dl_aarch64_gcs);
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switch (policy)
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{
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case GCS_POLICY_DISABLED:
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case GCS_POLICY_OVERRIDE:
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return;
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case GCS_POLICY_ENFORCED:
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check_gcs_depends (l, program, true);
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return;
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case GCS_POLICY_OPTIONAL:
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check_gcs_depends (l, program, false);
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return;
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default:
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/* All other policy values are not supported: abort. */
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unsupported ();
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}
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}
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/* Used to report error when prctl system call to enabled GCS fails. */
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void _dl_gcs_enable_failed (int code)
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{
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_dl_fatal_printf ("failed to enable GCS: %d\n", -code);
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}
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