On 07.06.25 18:53, wangfushuai wrote:
Add mo in /proc/[pid]/smaps to indicate vma is marked VM_MAYOVERLAY,
which means the file mapping may overlay in NOMMU system.
Fixes: b6b7a8faf05c ("mm/nommu: don't use VM_MAYSHARE for MAP_PRIVATE mappings")
Signed-off-by: wangfushuai <wangfushuai@xxxxxxxxx>
---
Documentation/filesystems/proc.rst | 1 +
fs/proc/task_mmu.c | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 2a17865dfe39..d280594656a3 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -609,6 +609,7 @@ encoded manner. The codes are the following:
uw userfaultfd wr-protect tracking
ss shadow/guarded control stack page
sl sealed
+ mo may overlay file mapping
== =======================================
Note that there is no guarantee that every flag and associated mnemonic will
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 27972c0749e7..ad08807847de 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -970,7 +970,11 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
[ilog2(VM_HUGEPAGE)] = "hg",
[ilog2(VM_NOHUGEPAGE)] = "nh",
[ilog2(VM_MERGEABLE)] = "mg",
+#ifdef CONFIG_MMU
[ilog2(VM_UFFD_MISSING)]= "um",
+#else
+ [ilog2(VM_MAYOVERLAY)] = "mo",
+#endif
[ilog2(VM_UFFD_WP)] = "uw",
#ifdef CONFIG_ARM64_MTE
[ilog2(VM_MTE)] = "mt",
That is mostly an internal-only flag. Why would we want to expose that
to user space?
--
Cheers,
David / dhildenb
