mm/mseal: fix mseal documentation for 32-bit kernels

mseal.o is built only for 64-bit kernels, so 32-bit kernels fall back to
sys_ni_syscall() and return -ENOSYS rather than -EPERM.

Drop architecture description in mseal.rst, since the arch feature doc has
the latest state of mseal for each architecture.

Fix the CONFIG_MSEAL_SYSTEM_MAPPINGS typo in init/Kconfig.

Link: https://lore.kernel.org/20260715131258.55499-1-leon.hwang@linux.dev
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Acked-by: Lance Yang <lance.yang@linux.dev>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Anand Moon <linux.amoon@gmail.com>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leon Hwang <leon.hwang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/userspace-api/mseal.rst

@@ -50,8 +50,8 @@ mseal syscall signature
          * The start address (``addr``) is not allocated.
          * The end address (``addr`` + ``len``) is not allocated.
          * A gap (unallocated memory) between start and end address.
-      - **-EPERM**:
-         * sealing is supported only on 64-bit CPUs, 32-bit is not supported.
+      - **-ENOSYS**:
+         * The kernel does not implement ``mseal()``.
 
    **Note about error return**:
       - For above error cases, users can expect the given memory range is
@@ -62,7 +62,8 @@ mseal syscall signature
         memory range could happen. However, those cases should be rare.
 
    **Architecture support**:
-      mseal only works on 64-bit CPUs, not 32-bit CPUs.
+      mseal is built only for 64-bit kernels. 32-bit kernels return
+      ``-ENOSYS``.
 
    **Idempotent**:
       users can call mseal multiple times. mseal on an already sealed memory
@@ -131,11 +132,11 @@ Use cases
 - Chrome browser: protect some security sensitive data structures.
 
 - System mappings:
-  The system mappings are created by the kernel and includes vdso, vvar,
+  The system mappings are created by the kernel and include vdso, vvar,
   vvar_vclock, vectors (arm compat-mode), sigpage (arm compat-mode), uprobes.
 
   Those system mappings are readonly only or execute only, memory sealing can
-  protect them from ever changing to writable or unmmap/remapped as different
+  protect them from ever changing to writable or unmapped/remapped as different
   attributes. This is useful to mitigate memory corruption issues where a
   corrupted pointer is passed to a memory management system.
 
@@ -143,9 +144,6 @@ Use cases
   the CONFIG_MSEAL_SYSTEM_MAPPINGS seals all system mappings of this
   architecture.
 
-  The following architectures currently support this feature: x86-64, arm64,
-  loongarch and s390.
-
   WARNING: This feature breaks programs which rely on relocating
   or unmapping system mappings. Known broken software at the time
   of writing includes CHECKPOINT_RESTORE, UML, gVisor, rr. Therefore

init/Kconfig

@@ -2123,7 +2123,7 @@ config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
 	  from a kernel perspective.
 
 	  After the architecture enables this, a distribution can set
-	  CONFIG_MSEAL_SYSTEM_MAPPING to manage access to the feature.
+	  CONFIG_MSEAL_SYSTEM_MAPPINGS to manage access to the feature.
 
 	  For complete descriptions of memory sealing, please see
 	  Documentation/userspace-api/mseal.rst