[PATCH v4 5/6] GDB: aarch64-linux: Reorganize GCS-related definitions

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Only native code should use struct user_gcs, so its definition should be
in a native-specific file and not in a file under gdb/arch/.

To fix this problem, create gdb/nat/aarch64-gcs-linux-ptrace.h and move
the struct user_gcs definition to it, as suggested by Luis.

To fix the use of struct user_gcs in gdb/aarch64-linuxt-dep.c, define a
macro with the size of the GCS regset in gdb/arch/aarch64-gcs-linux.h
and use it in aarch64-linux-tdep.c, as is done for other regsets and
following a suggestion from Simon Marchi.

Also, move the HWCAP_GCS definition to
gdb/nat/aarch64-gcs-linux-ptrace.h and create an AARCH64_HWCAP_GCS
definition in gdb/arch/aarch64-gcs-linux.h for use by target-dependent
code.

Similarly, move the SEGV_CPERR and PR_SHADOW_STACK_{ENABLE,WRITE,PUSH}
definitions, which were added by the GCS patches and are only used by
aarch64-linux target-dependent code, to gdb/arch/aarch64-gcs-linux.h
with an AARCH64_ prefix and adjust users.

Finally, I noticed that gdb/aarch64-linux-nat.c and
gdbserver/linux-aarch64-low.cc don't need anything from the
arch/aarch64-gcs-linux.h header, so make them not include it.

Suggested-by: Luis <luis.machado.foss@gmail.com>
Suggested-by: Simon Marchi <simark@simark.ca>
---
Changes since v3:
- Move HWCAP_GCS definition to gdb/nat/aarch64-gcs-linux-ptrace.h.
- Add AARCH64_HWCAP_GCS and use it in gdb/aarch64-linux-tdep.c.
- Move the SEGV_CPERR and PR_SHADOW_STACK_{ENABLE,WRITE,PUSH} definitions
  to gdb/arch/aarch64-gcs-linux.h with an AARCH64_ prefix.
- Remove inclusion of arch/aarch64-gcs-linux.h from gdb/aarch64-linux-nat.c
  and gdbserver/linux-aarch64-low.cc.

Changes since v2:
- Don't rename gdb/arch/aarch64-gcs-linux.h to gdb/arch/aarch64-linux.h,
  as suggested by Luis.
- Create gdb/nat/aarch64-gcs-linux-ptrace.h to contain definition of
  struct user_gcs, as suggested by Luis.
- Don't rename HWCAP_GCS to AARCH64_HWCAP_GCS, as suggested by Luis.
- Move definition of AARCH64_LINUX_SIZEOF_GCS_REGSET from
  gdb/aarch64-linux-tdep.h to gdb/arch/aarch64-gcs-linux.h, as suggested
  by Luis.
- Move changes to HWCAP_PACA to separate patch.

 gdb/Makefile.in                |  1 +
 gdb/aarch64-linux-nat.c        |  3 +--
 gdb/aarch64-linux-tdep.c       | 13 +++++-----
 gdb/arch/aarch64-gcs-linux.h   | 24 ++++++------------
 gdb/linux-tdep.h               | 11 ---------
 gdb/nat/aarch64-gcs-linux.h    | 45 ++++++++++++++++++++++++++++++++++
 gdbserver/linux-aarch64-low.cc |  2 +-
 7 files changed, 63 insertions(+), 36 deletions(-)
 create mode 100644 gdb/nat/aarch64-gcs-linux.h

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 3d9bc86a97fd..4a68189b4340 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -1548,6 +1548,7 @@ HFILES_NO_SRCDIR = \
 	moxie-tdep.h \
 	namespace.h \
 	nat/aarch64-fpmr-linux.h \
+	nat/aarch64-gcs-linux.h \
 	nat/aarch64-hw-point.h \
 	nat/aarch64-linux.h \
 	nat/aarch64-linux-hw-point.h \
diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 4b86ae9ebe16..52ace4aab411 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -33,6 +33,7 @@
 #include "aarch32-tdep.h"
 #include "arch/arm.h"
 #include "nat/aarch64-fpmr-linux.h"
+#include "nat/aarch64-gcs-linux.h"
 #include "nat/aarch64-linux.h"
 #include "nat/aarch64-linux-hw-point.h"
 #include "nat/aarch64-mte-linux-ptrace.h"
@@ -54,8 +55,6 @@
 #include "gdb_proc_service.h"
 #include "arch-utils.h"
 
-#include "arch/aarch64-gcs-linux.h"
-
 #include <string.h>
 
 #ifndef TRAP_HWBKPT
diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index 4ca05fba771d..d136b0f2145e 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -1736,8 +1736,9 @@ aarch64_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
 	  gcs_regmap, regcache_supply_regset, regcache_collect_regset
 	};
 
-      cb (".reg-aarch-gcs", sizeof (user_gcs), sizeof (user_gcs),
-	  &aarch64_linux_gcs_regset, "GCS registers", cb_data);
+      cb (".reg-aarch-gcs", AARCH64_LINUX_SIZEOF_GCS_REGSET,
+	  AARCH64_LINUX_SIZEOF_GCS_REGSET, &aarch64_linux_gcs_regset,
+	  "GCS registers", cb_data);
     }
 }
 
@@ -1763,7 +1764,7 @@ aarch64_linux_core_read_description (struct gdbarch *gdbarch,
      length.  */
   features.vq = aarch64_linux_core_read_vq_from_sections (gdbarch, abfd);
   features.pauth = hwcap & AARCH64_HWCAP_PACA;
-  features.gcs = features.gcs_linux = hwcap & HWCAP_GCS;
+  features.gcs = features.gcs_linux = hwcap & AARCH64_HWCAP_GCS;
   features.mte = hwcap2 & AARCH64_HWCAP2_MTE;
   features.fpmr = hwcap2 & AARCH64_HWCAP2_FPMR;
 
@@ -2612,7 +2613,7 @@ aarch64_linux_get_shadow_stack_pointer (gdbarch *gdbarch, regcache *regcache,
   if (status != REG_VALID)
     error (_("Can't read $gcspr."));
 
-  shadow_stack_enabled = features_enabled & PR_SHADOW_STACK_ENABLE;
+  shadow_stack_enabled = features_enabled & AARCH64_PR_SHADOW_STACK_ENABLE;
   return gcspr;
 }
 
@@ -2700,7 +2701,7 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
 
   if (si_code == AARCH64_SEGV_MTEAERR || si_code == AARCH64_SEGV_MTESERR)
     meaning = _("Memory tag violation");
-  else if (si_code == SEGV_CPERR && si_errno == 0)
+  else if (si_code == AARCH64_SEGV_CPERR && si_errno == 0)
     meaning = _("Guarded Control Stack error");
   else
     return;
@@ -2733,7 +2734,7 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch,
 	  uiout->field_string ("logical-tag", hex_string (ltag));
 	}
     }
-  else if (si_code != SEGV_CPERR)
+  else if (si_code != AARCH64_SEGV_CPERR)
     {
       uiout->text ("\n");
       uiout->text (_("Fault address unavailable"));
diff --git a/gdb/arch/aarch64-gcs-linux.h b/gdb/arch/aarch64-gcs-linux.h
index b31fc32daa03..4aa0cbd4def8 100644
--- a/gdb/arch/aarch64-gcs-linux.h
+++ b/gdb/arch/aarch64-gcs-linux.h
@@ -20,25 +20,17 @@
 #ifndef GDB_ARCH_AARCH64_GCS_LINUX_H
 #define GDB_ARCH_AARCH64_GCS_LINUX_H
 
-#include <stdint.h>
-
 /* Feature check for Guarded Control Stack.  */
-#ifndef HWCAP_GCS
-#define HWCAP_GCS (1ULL << 32)
-#endif
-
-/* Make sure we only define these if the kernel header doesn't.  */
-#ifndef GCS_MAGIC
+#define AARCH64_HWCAP_GCS (1ULL << 32)
 
-/* GCS state (NT_ARM_GCS).  */
+#define AARCH64_SEGV_CPERR 10 /* Control protection error.  */
 
-struct user_gcs
-{
-  uint64_t features_enabled;
-  uint64_t features_locked;
-  uint64_t gcspr_el0;
-};
+/* Flag which enables shadow stack in PR_SET_SHADOW_STACK_STATUS prctl.  */
+#define AARCH64_PR_SHADOW_STACK_ENABLE (1UL << 0)
+#define AARCH64_PR_SHADOW_STACK_WRITE (1UL << 1)
+#define AARCH64_PR_SHADOW_STACK_PUSH (1UL << 2)
 
-#endif /* GCS_MAGIC */
+/* The GCS regset consists of 3 64-bit registers.  */
+#define AARCH64_LINUX_SIZEOF_GCS_REGSET (3 * 8)
 
 #endif /* GDB_ARCH_AARCH64_GCS_LINUX_H */
diff --git a/gdb/linux-tdep.h b/gdb/linux-tdep.h
index 73d4832069f4..aee52eae0f4a 100644
--- a/gdb/linux-tdep.h
+++ b/gdb/linux-tdep.h
@@ -27,17 +27,6 @@
 struct inferior;
 struct regcache;
 
-#ifndef SEGV_CPERR
-#define SEGV_CPERR 10 /* Control protection error.  */
-#endif
-
-/* Flag which enables shadow stack in PR_SET_SHADOW_STACK_STATUS prctl.  */
-#ifndef PR_SHADOW_STACK_ENABLE
-#define PR_SHADOW_STACK_ENABLE (1UL << 0)
-#define PR_SHADOW_STACK_WRITE (1UL << 1)
-#define PR_SHADOW_STACK_PUSH (1UL << 2)
-#endif
-
 /* Enum used to define the extra fields of the siginfo type used by an
    architecture.  */
 enum linux_siginfo_extra_field_values
diff --git a/gdb/nat/aarch64-gcs-linux.h b/gdb/nat/aarch64-gcs-linux.h
new file mode 100644
index 000000000000..ddf8342a4284
--- /dev/null
+++ b/gdb/nat/aarch64-gcs-linux.h
@@ -0,0 +1,45 @@
+/* Common native Linux definitions for AArch64 Guarded Control Stack.
+
+   Copyright (C) 2025-2026 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+#ifndef GDB_NAT_AARCH64_GCS_LINUX_H
+#define GDB_NAT_AARCH64_GCS_LINUX_H
+
+#include <stdint.h>
+#include <asm/ptrace.h>
+
+/* Feature check for Guarded Control Stack.  */
+#ifndef HWCAP_GCS
+#define HWCAP_GCS (1ULL << 32)
+#endif
+
+/* Make sure we only define these if the kernel header doesn't.  */
+#ifndef GCS_MAGIC
+
+/* GCS state (NT_ARM_GCS).  */
+
+struct user_gcs
+{
+  uint64_t features_enabled;
+  uint64_t features_locked;
+  uint64_t gcspr_el0;
+};
+
+#endif /* GCS_MAGIC */
+
+#endif /* GDB_NAT_AARCH64_GCS_LINUX_H */
diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
index c44f75167141..a2588a6e2a9c 100644
--- a/gdbserver/linux-aarch64-low.cc
+++ b/gdbserver/linux-aarch64-low.cc
@@ -40,12 +40,12 @@
 
 #include "gdb_proc_service.h"
 #include "arch/aarch64.h"
-#include "arch/aarch64-gcs-linux.h"
 #include "arch/aarch64-mte-linux.h"
 #include "arch/aarch64-pauth-linux.h"
 #include "linux-aarch32-tdesc.h"
 #include "linux-aarch64-tdesc.h"
 #include "nat/aarch64-fpmr-linux.h"
+#include "nat/aarch64-gcs-linux.h"
 #include "nat/aarch64-mte-linux-ptrace.h"
 #include "nat/aarch64-scalable-linux-ptrace.h"
 #include "tdesc.h"