new file mode 100644
@@ -0,0 +1,168 @@
+/* This test program is part of GDB, the GNU debugger.
+
+ Copyright 2025 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <sys/auxv.h>
+#include <sys/syscall.h>
+#include <linux/prctl.h>
+
+/* Feature check for Guarded Control Stack. */
+#ifndef HWCAP_GCS
+#define HWCAP_GCS (1UL << 32)
+#endif
+
+#ifndef PR_GET_SHADOW_STACK_STATUS
+#define PR_GET_SHADOW_STACK_STATUS 74
+#define PR_SET_SHADOW_STACK_STATUS 75
+#define PR_SHADOW_STACK_ENABLE (1UL << 0)
+#endif
+
+/* We need to use a macro to call prctl because after GCS is enabled, it's not
+ possible to return from the function which enabled it. This is because the
+ return address of the calling function isn't on the GCS. */
+#define my_syscall2(num, arg1, arg2) \
+ ({ \
+ register long _num __asm__("x8") = (num); \
+ register long _arg1 __asm__("x0") = (long)(arg1); \
+ register long _arg2 __asm__("x1") = (long)(arg2); \
+ register long _arg3 __asm__("x2") = 0; \
+ register long _arg4 __asm__("x3") = 0; \
+ register long _arg5 __asm__("x4") = 0; \
+ \
+ __asm__ volatile("svc #0\n" \
+ : "=r"(_arg1) \
+ : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \
+ "r"(_arg5), "r"(_num) \
+ : "memory", "cc"); \
+ _arg1; \
+ })
+
+#define get_gcspr(void) \
+ ({ \
+ unsigned long *gcspr; \
+ \
+ /* Get GCSPR_EL0. */ \
+ asm volatile("mrs %0, S3_3_C2_C5_1" : "=r"(gcspr) : : "cc"); \
+ \
+ gcspr; \
+ })
+
+static unsigned long *handler_gcspr = 0;
+
+static void
+handler (int sig)
+{
+ handler_gcspr = get_gcspr ();
+}
+
+static int __attribute__ ((unused))
+called_from_gdb (int val)
+{
+ return val + 1;
+}
+
+/* Corrupt the return address to see if GDB will report a SIGSEGV with the expected
+ $_siginfo.si_code. */
+static void __attribute__ ((noinline))
+normal_function2 (void)
+{
+ /* x30 holds the return address. */
+ register unsigned long x30 __asm__("x30") __attribute__ ((unused));
+
+ /* Cause a GCS exception. */
+ x30 = 0xbadc0ffee;
+ __asm__ volatile("ret\n");
+}
+
+static inline void __attribute__ ((__always_inline__))
+inline_function2 (void)
+{
+ normal_function2 ();
+}
+
+/* Corrupt the return address to see if GDB will report a GCS error in this
+ function's frame . */
+static void __attribute__ ((noinline))
+normal_function1 (void)
+{
+ /* x30 holds the return address. */
+ register unsigned long x30 __asm__ ("x30") __attribute__ ((unused));
+ x30 = 0xbadc0ffee;
+ inline_function2 ();
+}
+
+static inline void __attribute__ ((__always_inline__))
+inline_function1 (void)
+{
+ normal_function1 ();
+}
+
+int
+main (void)
+{
+ if (!(getauxval (AT_HWCAP) & HWCAP_GCS))
+ {
+ fprintf (stderr, "GCS support not found in AT_HWCAP\n");
+ return EXIT_FAILURE;
+ }
+
+ /* Force shadow stacks on, our tests *should* be fine with or
+ without libc support and with or without this having ended
+ up tagged for GCS and enabled by the dynamic linker. We
+ can't use the libc prctl() function since we can't return
+ from enabling the stack. Also lock GCS if not already
+ locked so we can test behaviour when it's locked. */
+ unsigned long gcs_mode;
+ int ret = my_syscall2 (__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &gcs_mode);
+ if (ret)
+ {
+ fprintf (stderr, "Failed to read GCS state: %d\n", ret);
+ return EXIT_FAILURE;
+ }
+
+ if (!(gcs_mode & PR_SHADOW_STACK_ENABLE))
+ {
+ gcs_mode = PR_SHADOW_STACK_ENABLE;
+ ret = my_syscall2 (__NR_prctl, PR_SET_SHADOW_STACK_STATUS, gcs_mode);
+ if (ret)
+ {
+ fprintf (stderr, "Failed to configure GCS: %d\n", ret);
+ return EXIT_FAILURE;
+ }
+ }
+
+ /* This is used by GDB. */
+ __attribute__((unused)) unsigned long *gcspr = get_gcspr ();
+
+ struct sigaction act = { 0 };
+
+ act.sa_handler = &handler; /* Break here. */
+ if (sigaction (SIGUSR1, &act, NULL) == -1)
+ {
+ perror ("sigaction");
+ exit (EXIT_FAILURE);
+ }
+
+ raise (SIGUSR1);
+
+ inline_function1 ();
+
+ /* Avoid returning, in case libc doesn't understand GCS. */
+ exit (EXIT_SUCCESS);
+}
new file mode 100644
@@ -0,0 +1,78 @@
+# Copyright 2025 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# Test a binary that uses a Guarded Control Stack.
+
+require allow_aarch64_gcs_tests
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
+ return
+}
+
+set linespec ${srcfile}:[gdb_get_line_number "Break here"]
+
+if ![runto ${linespec}] {
+ return
+}
+
+gdb_test "print \$gcs_features_enabled" \
+ [string_to_regexp { = [ PR_SHADOW_STACK_ENABLE ]}] \
+ "GCS is enabled"
+
+gdb_test "print \$gcspr" ". = \\(void \\*\\) $hex" "GDB knows about gcspr"
+gdb_test "print \$gcspr == gcspr" ". = 1" "GDB has the correct gcspr value"
+gdb_test_no_output "set \$gcspr_in_main = \$gcspr" \
+ "save gcspr value in main for later"
+
+# If the inferior function call fails, we don't want the tests following it
+# to be affected.
+gdb_test_no_output "set unwindonsignal on"
+gdb_test "print called_from_gdb (41)" ". = 42" "call inferior function"
+
+gdb_test "break handler" "Breakpoint \[0-9\]+ .*aarch64-gcs.c, line \[0-9\]+\\."
+gdb_test "handle SIGUSR1 nostop" \
+ ".*\r\nSIGUSR1\\s+No\\s+Yes\\s+Yes\\s+User defined signal 1" \
+ "let the inferior receive SIGUSR1 uninterrupted"
+gdb_test "continue" \
+ ".*\r\nBreakpoint \[0-9\]+, handler \\(sig=10\\) at .*aarch64-gcs.c.*handler_gcspr = get_gcspr \\(\\);" \
+ "continue to signal handler"
+
+gdb_test_no_output "set \$gcspr_in_handler = \$gcspr" \
+ "save gcspr value in handler for later"
+# Select the frame above the <signal handler called> frame, which makes GDB
+# unwind the gcspr from the signal frame GCS context.
+gdb_test "frame 2" "#2 ($hex in )?\\S+ \\(.*\\) (at|from) \\S+.*" \
+ "reached frame 2"
+gdb_test "print \$gcspr" ". = \\(void \\*\\) $hex" "gcspr in frame level 2"
+gdb_test "print \$gcspr == \$gcspr_in_handler + 8" ". = 1" \
+ "gcspr unwound from signal context is correct"
+
+gdb_test "continue" \
+ [multi_line \
+ "Continuing\\." \
+ "" \
+ "Program received signal SIGSEGV, Segmentation fault" \
+ "Guarded Control Stack error\\." \
+ "normal_function2 \\(\\) at .*aarch64-gcs.c:$decimal" \
+ "${decimal}\\s+__asm__ volatile\\(\"ret\\\\n\"\\);"] \
+ "continue to SIGSEGV"
+
+gdb_test "print \$_siginfo.si_code" ". = 10" \
+ "test value of si_code when GCS SIGSEGV happens"
+# The GCS grows down, and there are two real frames until main.
+gdb_test "print \$gcspr == \$gcspr_in_main - 16" ". = 1" \
+ "test value of gcspr when GCS SIGSEGV happens"
@@ -5094,6 +5094,64 @@ gdb_caching_proc allow_aarch64_mops_tests {} {
return $allow_mops_tests
}
+# Run a test on the target to see if it supports Aarch64 GCS extensions.
+# Return 0 if so, 1 if it does not. Note this causes a restart of GDB.
+
+gdb_caching_proc allow_aarch64_gcs_tests {} {
+ global srcdir subdir gdb_prompt inferior_exited_re
+
+ set me "allow_aarch64_gcs_tests"
+
+ if { ![is_aarch64_target]} {
+ return 0
+ }
+
+ # Compile a program that tests the GCS feature.
+ set src {
+ #include <stdbool.h>
+ #include <sys/auxv.h>
+
+ /* Feature check for Guarded Control Stack. */
+ #ifndef HWCAP_GCS
+ #define HWCAP_GCS (1UL << 32)
+ #endif
+
+ int main (void) {
+ bool gcs_supported = getauxval (AT_HWCAP) & HWCAP_GCS;
+
+ /* Return success if GCS is supported. */
+ return !gcs_supported;
+ }
+ }
+
+ if {![gdb_simple_compile $me $src executable]} {
+ return 0
+ }
+
+ # Compilation succeeded so now run it via gdb.
+ clean_restart $obj
+ gdb_run_cmd
+ gdb_expect {
+ -re ".*$inferior_exited_re with code 01.*${gdb_prompt} $" {
+ verbose -log "\n$me gcs support not detected"
+ set allow_gcs_tests 0
+ }
+ -re ".*$inferior_exited_re normally.*${gdb_prompt} $" {
+ verbose -log "\n$me: gcs support detected"
+ set allow_gcs_tests 1
+ }
+ default {
+ warning "\n$me: default case taken"
+ set allow_gcs_tests 0
+ }
+ }
+ gdb_exit
+ remote_file build delete $obj
+
+ verbose "$me: returning $allow_gcs_tests" 2
+ return $allow_gcs_tests
+}
+
# A helper that compiles a test case to see if __int128 is supported.
proc gdb_int128_helper {lang} {
return [gdb_can_simple_compile "i128-for-$lang" {