[PATCH v3 1/2] rtld: Enable MTE for stack when specified in .dynamic
claudiu.zissulescu-ianculescu@oracle.com
claudiu.zissulescu-ianculescu@oracle.com
Tue Mar 10 14:11:06 GMT 2026
From: Cupertino Miranda <cupertino.miranda@oracle.com>
This patch enables Memory Tag Extension (MTE) for stack tagging in the
rtld. Parse DT_AARCH64_MEMTAG_STACK and DT_AARCH64_MEMTAG_MODE from
the main program and enable stack memory tagging in the dynamic
loader, as described in ARM's ABI [1] documentation.
Ref:
[1] https://github.com/ARM-software/abi-aa/blob/main/memtagabielf64/memtagabielf64.rst
---
elf/elf.h | 7 +-
sysdeps/aarch64/Makefile | 1 +
sysdeps/aarch64/cpu-features.h | 12 +++
sysdeps/aarch64/dl-mte.c | 85 +++++++++++++++++++
sysdeps/aarch64/dl-prop.h | 4 +
sysdeps/unix/sysv/linux/aarch64/Makefile | 4 +
.../unix/sysv/linux/aarch64/dl-mte-stack.c | 45 ++++++++++
7 files changed, 157 insertions(+), 1 deletion(-)
create mode 100644 sysdeps/aarch64/dl-mte.c
create mode 100644 sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c
diff --git a/elf/elf.h b/elf/elf.h
index 46a01281cb..02c4125cb1 100644
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -3039,7 +3039,12 @@ enum
#define DT_AARCH64_BTI_PLT (DT_LOPROC + 1)
#define DT_AARCH64_PAC_PLT (DT_LOPROC + 3)
#define DT_AARCH64_VARIANT_PCS (DT_LOPROC + 5)
-#define DT_AARCH64_NUM 6
+#define DT_AARCH64_MEMTAG_MODE (DT_LOPROC + 9)
+#define DT_AARCH64_MEMTAG_HEAP (DT_LOPROC + 11)
+#define DT_AARCH64_MEMTAG_STACK (DT_LOPROC + 12)
+#define DT_AARCH64_MEMTAG_GLOBALS (DT_LOPROC + 13)
+#define DT_AARCH64_MEMTAG_GLOBALSSZ (DT_LOPROC + 15)
+#define DT_AARCH64_NUM 16
/* AArch64 specific values for the st_other field. */
#define STO_AARCH64_VARIANT_PCS 0x80
diff --git a/sysdeps/aarch64/Makefile b/sysdeps/aarch64/Makefile
index d6c5cc96ca..dfbc33d2f4 100644
--- a/sysdeps/aarch64/Makefile
+++ b/sysdeps/aarch64/Makefile
@@ -4,6 +4,7 @@ ifeq ($(subdir),elf)
sysdep-dl-routines += \
dl-bti \
dl-gcs \
+ dl-mte \
# sysdep-dl-routines
tests += \
diff --git a/sysdeps/aarch64/cpu-features.h b/sysdeps/aarch64/cpu-features.h
index 1fe35d986b..91e0ce9a90 100644
--- a/sysdeps/aarch64/cpu-features.h
+++ b/sysdeps/aarch64/cpu-features.h
@@ -74,4 +74,16 @@ struct cpu_features
bool mops;
};
+#define ARCH_MTE_MODE_SYNC (1 << 1)
+#define ARCH_MTE_MODE_ASYNC (1 << 2)
+#define AARCH64_CPU_FEATURE_MTE_STATE_STACK (1 << 3)
+
+#define AARCH64_CPU_FEATURE_MTE_STATE_MODE_MASK (0x3)
+#define AARCH64_CPU_FEATURE_MTE_STATE_MODE_ASYNC (1)
+#define AARCH64_CPU_FEATURE_MTE_STATE_MODE_SYNC (1 << 1)
+
+#ifndef ARCH_INIT_MEMORY_STACK_TAGGING
+# define ARCH_INIT_MEMORY_STACK_TAGGING _dl_mte_stack_protect
+#endif
+
#endif /* _CPU_FEATURES_AARCH64_H */
diff --git a/sysdeps/aarch64/dl-mte.c b/sysdeps/aarch64/dl-mte.c
new file mode 100644
index 0000000000..e73c5311a6
--- /dev/null
+++ b/sysdeps/aarch64/dl-mte.c
@@ -0,0 +1,85 @@
+/* AArch64 MTE Stack functions.
+ Copyright (C) 2026 Free Software Foundation, Inc.
+
+ 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 <errno.h>
+#include <ldsodefs.h>
+#include <libintl.h>
+#include <stackinfo.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+extern int _dl_mte_mode (void);
+
+void
+_dl_mte_stack_check (struct link_map *l,
+ const char *program __attribute__((unused)))
+{
+ ElfW (Dyn) *d;
+ bool mte_enabled = false;
+ bool mte_mode_selected = false;
+
+ for (d = l->l_ld; d->d_tag != DT_NULL; ++d)
+ {
+ if (d->d_tag == DT_AARCH64_MEMTAG_STACK)
+ {
+ GLRO (dl_aarch64_cpu_features).mte_state
+ |= AARCH64_CPU_FEATURE_MTE_STATE_STACK;
+ mte_enabled = true;
+ }
+ else if (d->d_tag == DT_AARCH64_MEMTAG_MODE)
+ {
+ GLRO (dl_aarch64_cpu_features).mte_state
+ &= ~AARCH64_CPU_FEATURE_MTE_STATE_MODE_MASK;
+ if (d->d_un.d_val == 1)
+ GLRO (dl_aarch64_cpu_features).mte_state
+ |= AARCH64_CPU_FEATURE_MTE_STATE_MODE_ASYNC;
+ else
+ GLRO (dl_aarch64_cpu_features).mte_state
+ |= AARCH64_CPU_FEATURE_MTE_STATE_MODE_SYNC;
+ mte_mode_selected = true;
+ }
+ }
+
+ if (mte_enabled && mte_mode_selected)
+ {
+ int errval = 0;
+ _dl_mte_mode ();
+ GL (dl_stack_prot_flags) |= PROT_MTE;
+
+ uintptr_t page = ((uintptr_t) __libc_stack_end
+ & -(uintptr_t) GLRO (dl_pagesize));
+
+ if (__mprotect ((void *) page, GLRO (dl_pagesize),
+ GL (dl_stack_prot_flags)
+#if _STACK_GROWS_DOWN
+ | PROT_GROWSDOWN
+#elif _STACK_GROWS_UP
+ | PROT_GROWSUP
+#endif
+ ) != 0)
+ errval = errno;
+
+ if (errval != 0)
+ {
+ const char *name = "MTE Stack";
+ struct dl_exception exception;
+ _dl_exception_create (&exception, name,
+ N_("cannot set stack with PROT_MTE"));
+ _dl_signal_exception (errval, &exception, NULL);
+ }
+ }
+}
diff --git a/sysdeps/aarch64/dl-prop.h b/sysdeps/aarch64/dl-prop.h
index cf236df59b..2ca0fd0f62 100644
--- a/sysdeps/aarch64/dl-prop.h
+++ b/sysdeps/aarch64/dl-prop.h
@@ -27,11 +27,15 @@ extern void _dl_bti_check (struct link_map *, const char *)
extern void _dl_gcs_check (struct link_map *, const char *, int)
attribute_hidden;
+extern void _dl_mte_stack_check (struct link_map *, const char *)
+ attribute_hidden;
+
static inline void __attribute__ ((always_inline))
_rtld_main_check (struct link_map *m, const char *program)
{
_dl_bti_check (m, program);
_dl_gcs_check (m, program, 0);
+ _dl_mte_stack_check (m, program);
}
static inline void __attribute__ ((always_inline))
diff --git a/sysdeps/unix/sysv/linux/aarch64/Makefile b/sysdeps/unix/sysv/linux/aarch64/Makefile
index 57461fded7..a2e79cf3d6 100644
--- a/sysdeps/unix/sysv/linux/aarch64/Makefile
+++ b/sysdeps/unix/sysv/linux/aarch64/Makefile
@@ -9,6 +9,10 @@ modules-names += \
LDFLAGS-tst-tlsdesc-pac = -rdynamic
$(objpfx)tst-tlsdesc-pac.out: $(objpfx)tst-tlsdesc-pac-mod.so
+
+sysdep-dl-routines += \
+ dl-mte-stack \
+ # sysdep-dl-routines
endif
ifeq ($(subdir),misc)
diff --git a/sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c b/sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c
new file mode 100644
index 0000000000..c93ca6a670
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/aarch64/dl-mte-stack.c
@@ -0,0 +1,45 @@
+/* Memory tagging handling for GNU dynamic linker. AArch64 version.
+ Copyright (C) 2026 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 <cpu-features.h>
+#include <ldsodefs.h>
+#include <sys/prctl.h>
+
+#define MTE_ALLOWED_TAGS (0xfffe << PR_MTE_TAG_SHIFT)
+
+int
+_dl_mte_mode (void)
+{
+ int err = 0;
+
+ if (GLRO (dl_aarch64_cpu_features).mte_state
+ & AARCH64_CPU_FEATURE_MTE_STATE_MODE_SYNC)
+ err = __prctl (PR_SET_TAGGED_ADDR_CTRL,
+ (PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_SYNC | MTE_ALLOWED_TAGS),
+ 0, 0, 0);
+ else if (GLRO (dl_aarch64_cpu_features).mte_state
+ & AARCH64_CPU_FEATURE_MTE_STATE_MODE_ASYNC)
+ err = __prctl (PR_SET_TAGGED_ADDR_CTRL,
+ (PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_ASYNC
+ | MTE_ALLOWED_TAGS),
+ 0, 0, 0);
+
+ return (err != 0
+ && (GLRO (dl_aarch64_cpu_features).mte_state
+ & AARCH64_CPU_FEATURE_MTE_STATE_MODE_MASK) != 0);
+}
--
2.53.0
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