Re: [PATCH 3/3] mm/mseal: remove further superfluous comments, do_mseal()

[Andrew Morton]

On Thu, 16 Jul 2026 14:43:11 +0100 "Lorenzo Stoakes (ARM)" <ljs@xxxxxxxxxx> wrote:

> There's no need to abstract do_mseal() any longer so put the system call
> implementation in the system call declaration.
> 
> The comment around do_mseal() is strangely formatted, overly long and adds
> a lot of superfluous information that the code already provides, so boil it
> down to the essentials.
> 

This patch
(https://lore.kernel.org/20260716-mseal-fixups-v1-3-3a9609bf041b@xxxxxxxxxx)
overlaps muchly with Leon's "mm/mseal: fix mseal documentation for
32-bit kernels"
(https://lore.kernel.org/20260715131258.55499-1-leon.hwang@xxxxxxxxx).

I'll remove the mseal.c changes from Leon's patch and I'll retain the
rest of that patch, after adjusting its changelog.  Please check all of
this!


Here's what's left of Leon's patch:

From: Leon Hwang <leon.hwang@xxxxxxxxx>
Subject: mm/mseal: fix mseal documentation for 32-bit kernels
Date: Wed, 15 Jul 2026 21:12:58 +0800

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@xxxxxxxxx
Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
Acked-by: Lance Yang <lance.yang@xxxxxxxxx>
Cc: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Cc: Anand Moon <linux.amoon@xxxxxxxxx>
Cc: Doug Anderson <dianders@xxxxxxxxxxxx>
Cc: Gary Guo <gary@xxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Leon Hwang <leon.hwang@xxxxxxxxx>
Cc: Liam R. Howlett <liam@xxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <ljs@xxxxxxxxxx>
Cc: Miguel Ojeda <ojeda@xxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Pedro Falcato <pfalcato@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 Documentation/userspace-api/mseal.rst |   14 ++++++--------
 init/Kconfig                          |    2 +-
 2 files changed, 7 insertions(+), 9 deletions(-)

--- a/Documentation/userspace-api/mseal.rst~mm-mseal-fix-mseal-documentation-for-32-bit-kernels
+++ a/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
--- a/init/Kconfig~mm-mseal-fix-mseal-documentation-for-32-bit-kernels
+++ a/init/Kconfig
@@ -2120,7 +2120,7 @@ config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPIN
 	  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
_