linux: Add mseal syscall support

It has been added on Linux 6.10 (8be7258aad44b5e25977a98db136f677fa6f4370) as a way to block operations such as mapping, moving to another location, shrinking the size, expanding the size, or modifying it to a pre-existing memory mapping. Although the system only works on 64-bit CPUs, the entrypoint was added for all ABIs (since the kernel might eventually implement it for additional ones and/or the ABI can execute on a 64-bit kernel). Checked on x86_64-linux-gnu and aarch64-linux-gnu. Reviewed-by: Collin Funk <collin.funk1@gmail.com>
2025-11-14 04:22:38 +03:00 · 2025-11-10 15:03:05 -03:00
parent a9c426bcca
commit 3d52fd274e
40 changed files with 280 additions and 0 deletions
--- a/5
+++ b/5
@@ -21,6 +21,11 @@ Major new features:
  platforms supporting _Float128) _Float128_t, introduced in TS
  18661-3:2015, have been added to <math.h>.

+* On Linux, the mseal function has been added.  It allows for sealing
+  memory mappings to prevent further changes during process execution,
+  such as changes to protection permissions, unmapping, relocation to
+  another location, or shrinking the size.
+
 Deprecated and removed features, and other changes affecting compatibility:

 * Support for dumped heaps has been removed - malloc_set_state() now always
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -3126,6 +3126,75 @@ process memory, no matter how it was allocated.  However, portable use
 of the function requires that it is only used with memory regions
 returned by @code{mmap} or @code{mmap64}.

+@deftypefun int mseal (void *@var{address}, size_t @var{length}, unsigned long @var{flags})
+@standards{Linux, sys/mman.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+
+A successful call to the @code {mseal} function protects the memory
+range @var{address} of @var{length} bytes, previously allocated with
+@code{mmap} or @code{mremap}, against further metadata changes, such
+as:
+
+@itemize @bullet
+@item
+Unmapping, moving to another location, extending or shrinking the size,
+via @code{munmap} and @code{mremap}.
+
+@item
+Moving or expanding a different VMA into the current location, via
+@code{mremap}.
+
+@item
+Modifying the memory range with @code{mmap} along with the flag @code{MAP_FIXED}.
+
+@item
+Change the protection flags with @code{mprotect} or @code{pkey_mprotect}.  Also
+for certain destructive @code{madvise} behaviours (@code{MADV_DONTNEED},
+@code{MADV_FREE}, @code{MADV_DONTNEED_LOCKED}, and @code{MADV_WIPEONFORK}),
+@code{mseal} only blocks the operation if the protection key associated with
+the memory denies write.
+
+@item
+Destructive behaviors on anonymous memory, such as @code{madvice} with
+@code{MADV_DONTNEED}.
+@end itemize
+
+The @var{address} must be an allocated virtual memory done by @code{mmap}
+or @code{mremap}, and it must be page-aligned.  The end address (@var{address}
+plus @var{length}) must be within an allocated virtual memory range.  There
+should be no unallocated memory between the start and end of the address range.
+
+The @var{flags} is currently unused.
+
+The @code{mseal} function returns @math{0} on success and @math{-1} on
+failure.
+
+The following @code{errno} error conditions are defined for this
+function:
+
+@table @code
+@item EPERM
+The system blocked the operation, and the given address range is unmodified
+without a partial update.  This error is also returned when @code{mseal} is
+issued on a 32-bit CPU (sealing is currently supported only on 64-bit CPUs,
+although 32-bit binaries running on a 64-bit kernel are supported).
+
+@item ENOMEM
+Either the @var{address} is not allocated, or the end address is not within the
+allocation, or there is unallocated memory between the start and end address.
+
+@item ENOSYS
+The kernel does not support the @code{mseal} syscall.
+
+@end table
+@end deftypefun
+
+@strong{NB:} The memory sealing changes the lifetime of a mapping, where the
+sealing memory could not be unmapped until the process terminates or replaces
+the process image through @code{execve} function.  The sealed mappings are
+inherited through @code{fork}.
+
+
@subsection Memory Protection Keys

@cindex memory protection key
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -205,6 +205,8 @@ tests += \
  tst-misalign-clone \
  tst-mlock2 \
  tst-mount \
+  tst-mseal \
+  tst-mseal-pkey \
  tst-ntp_adjtime \
  tst-ntp_gettime \
  tst-ntp_gettimex \
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -339,6 +339,9 @@ libc {
    cfsetispeed;
    cfsetspeed;
  }
+  GLIBC_2.43 {
+    mseal;
+  }
  GLIBC_PRIVATE {
    # functions used in other libraries
    __syscall_rt_sigqueueinfo;
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2770,4 +2770,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -3117,6 +3117,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/arc/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
@@ -2531,4 +2531,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@@ -2823,6 +2823,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -2820,6 +2820,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/bits/mman-shared.h
+++ b/sysdeps/unix/sysv/linux/bits/mman-shared.h
@@ -80,6 +80,16 @@ int pkey_free (int __key) __THROW;
   range.  */
 int pkey_mprotect (void *__addr, size_t __len, int __prot, int __pkey) __THROW;

+/* Seal the address range to avoid further modifications, such as remapping to
+   shrink or expand the VMA, changing protection permission with mprotect,
+   unmap with munmap, or destructive semantics such as madvise with
+   MADV_DONTNEED.
+
+   The address range must be a valid VMA, without any gaps (unallocated
+   memory) between the start and end, and ADDR must be page-aligned (LEN will
+   be page-aligned implicitly).  */
+int mseal (void *__addr, size_t __len, unsigned long flags) __THROW;
+
 __END_DECLS

 #endif /* __USE_GNU */
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2807,4 +2807,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2844,6 +2844,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -3027,6 +3027,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -261,4 +261,12 @@
 # define __ASSUME_FCHMODAT2 0
 #endif

+/* The mseal system call was introduced across all architectures in Linux 6.10
+   (although only supported on 64-bit CPUs).  */
+#if __LINUX_KERNEL_VERSION >= 0x060A00
+# define __ASSUME_MSEAL 1
+#else
+# define __ASSUME_MSEAL 0
+#endif
+
 #endif /* kernel-features.h */
--- a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
@@ -2291,4 +2291,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -2803,6 +2803,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2970,6 +2970,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2856,4 +2856,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@@ -2853,4 +2853,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2933,6 +2933,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2939,6 +2939,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2841,6 +2841,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/or1k/libc.abilist
+++ b/sysdeps/unix/sysv/linux/or1k/libc.abilist
@@ -2281,4 +2281,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -3160,6 +3160,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -3205,6 +3205,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2914,6 +2914,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2990,4 +2990,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
@@ -2534,4 +2534,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2734,4 +2734,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -3158,6 +3158,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2951,6 +2951,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@@ -2850,6 +2850,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2847,6 +2847,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -3181,6 +3181,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2817,6 +2817,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/syscalls.list
+++ b/sysdeps/unix/sysv/linux/syscalls.list
@@ -39,6 +39,7 @@ mlockall	-	mlockall	i:i	mlockall
 mount		EXTRA	mount		i:sssUp	__mount	mount
 mount_setattr	EXTRA	mount_setattr	i:isUpU	mount_setattr
 move_mount	EXTRA	move_mount	i:isisU	move_mount
+mseal		EXTRA	mseal		i:bUU	__mseal	mseal
 munlock		-	munlock		i:aU	munlock
 munlockall	-	munlockall	i:	munlockall
 nfsservctl	EXTRA	nfsservctl	i:ipp	__compat_nfsservctl	nfsservctl@GLIBC_2.0:GLIBC_2.28
--- a/sysdeps/unix/sysv/linux/tst-mseal-pkey.c
+++ b/sysdeps/unix/sysv/linux/tst-mseal-pkey.c
@@ -0,0 +1,84 @@
+/* Basic tests for mseal and pkey.
+   Copyright (C) 2025 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 <errno.h>
+#include <sys/mman.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+
+static int
+do_test (void)
+{
+  TEST_VERIFY (mseal (MAP_FAILED, 0, 0) == -1);
+  if (errno == ENOSYS || errno == EPERM)
+    FAIL_UNSUPPORTED ("kernel does not support mseal");
+  TEST_COMPARE (errno, EINVAL);
+
+  int key = pkey_alloc (0, 0);
+  if (key < 0)
+    {
+      if (errno == ENOSYS)
+        FAIL_UNSUPPORTED
+          ("kernel does not support memory protection keys");
+      if (errno == EINVAL)
+        FAIL_UNSUPPORTED
+          ("CPU does not support memory protection keys: %m");
+      if (errno == ENOSPC)
+        FAIL_UNSUPPORTED
+          ("no keys available or kernel does not support memory"
+           " protection keys");
+      FAIL_EXIT1 ("pkey_alloc: %m");
+    }
+
+  long pagesize = xsysconf (_SC_PAGESIZE);
+
+  void *page = xmmap (NULL, pagesize, PROT_READ | PROT_WRITE,
+		      MAP_ANONYMOUS | MAP_PRIVATE, -1);
+
+  TEST_COMPARE (pkey_mprotect (page, pagesize, PROT_READ | PROT_WRITE,
+			       key), 0);
+
+  TEST_VERIFY_EXIT (mseal (page, pagesize, 0) == 0);
+
+  /* For certain destructive madvise behaviours (MADV_DONTNEED,
+     MADV_FREE, MADV_DONTNEED_LOCKED, and MADV_WIPEONFORK), mseal
+     only blocks the operation if the PKRU denies write.  */
+  TEST_VERIFY_EXIT (pkey_set (key, 0) == 0);
+  TEST_COMPARE (madvise (page, pagesize, MADV_DONTNEED), 0);
+
+  /* The other mapping operation change are always blocked,
+     regardless of PKRU state.  */
+  TEST_COMPARE (pkey_mprotect (page, pagesize, PROT_READ, key), -1);
+  TEST_COMPARE (errno, EPERM);
+
+  TEST_COMPARE (mprotect (page, pagesize, PROT_READ), -1);
+  TEST_COMPARE (errno, EPERM);
+
+  TEST_VERIFY_EXIT (pkey_set (key, PKEY_DISABLE_WRITE) == 0);
+  TEST_COMPARE (madvise (page, pagesize, MADV_DONTNEED), -1);
+  TEST_COMPARE (errno, EPERM);
+
+  TEST_COMPARE (mprotect (page, pagesize, PROT_READ), -1);
+  TEST_COMPARE (errno, EPERM);
+  TEST_COMPARE (munmap (page, pagesize),-1);
+  TEST_COMPARE (errno, EPERM);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
--- a/sysdeps/unix/sysv/linux/tst-mseal.c
+++ b/sysdeps/unix/sysv/linux/tst-mseal.c
@@ -0,0 +1,67 @@
+/* Basic tests for mseal.
+   Copyright (C) 2025 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 <errno.h>
+#include <sys/mman.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+
+static int
+do_test (void)
+{
+  TEST_VERIFY (mseal (MAP_FAILED, 0, 0) == -1);
+  if (errno == ENOSYS || errno == EPERM)
+    FAIL_UNSUPPORTED ("kernel does not support mseal");
+  TEST_COMPARE (errno, EINVAL);
+
+  size_t pagesize = getpagesize ();
+  void *p = xmmap (NULL, 4 * pagesize, PROT_READ,
+		   MAP_ANONYMOUS | MAP_PRIVATE, -1);
+  xmunmap (p + 2 * pagesize, pagesize);
+
+  /* Unaligned address.  */
+  TEST_VERIFY_EXIT (mseal (p + 1, pagesize, 0) == -1);
+  TEST_COMPARE (errno, EINVAL);
+
+  /* Length too big.  */
+  TEST_VERIFY_EXIT (mseal (p, 3 * pagesize, 0) == -1);
+  TEST_COMPARE (errno, ENOMEM);
+
+  TEST_VERIFY_EXIT (mseal (p, pagesize, 0) == 0);
+  /* Apply the same seal should be idempotent.  */
+  TEST_VERIFY_EXIT (mseal (p, pagesize, 0) == 0);
+
+  TEST_VERIFY_EXIT (mprotect (p, pagesize, PROT_WRITE) == -1);
+  TEST_COMPARE (errno, EPERM);
+
+  TEST_VERIFY_EXIT (munmap (p, pagesize) == -1);
+  TEST_COMPARE (errno, EPERM);
+
+  TEST_VERIFY_EXIT (mremap (p, pagesize, 2 * pagesize, 0) == MAP_FAILED);
+  TEST_COMPARE (errno, EPERM);
+
+  TEST_VERIFY_EXIT (madvise (p, pagesize, MADV_DONTNEED) == -1);
+  TEST_COMPARE (errno, EPERM);
+
+  xmunmap (p + pagesize, pagesize);
+  xmunmap (p + 3 * pagesize, pagesize);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2766,6 +2766,7 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2785,4 +2785,5 @@ GLIBC_2.42 ullabs F
 GLIBC_2.43 __memset_explicit_chk F
 GLIBC_2.43 memalignment F
 GLIBC_2.43 memset_explicit F
+GLIBC_2.43 mseal F
 GLIBC_2.43 umaxabs F