[PATCH RFC 2/2] mm, madvise: move prctl_set_vma() to mm/madvise.c

[Vlastimil Babka <vbabka@suse.cz>]

Setting anon_name is done via madvise_set_anon_name() and behaves a lot
of like other madvise operations. However, apparently because madvise()
has lacked the 4th argument and prctl() not, the userspace entry point
has been implemented via prctl(PR_SET_VMA, ...) and handled first by
prctl_set_vma().

Currently prctl_set_vma() lives in kernel/sys.c but it's mm code so move
it under mm. mm/madvise.c seems to be the most straightforward place as
that's where madvise_set_anon_name() lives, so we can stop declaring the
latter in the header and instead declare prctl_set_vma(). It's not ideal
as prctl is not madvise, but that's the reality we live in, as described
above.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 include/linux/mm.h | 13 +++++------
 kernel/sys.c       | 64 ------------------------------------------------------
 mm/madvise.c       | 59 +++++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 63 insertions(+), 73 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e0549f3d681f6c7a78e8dfa341a810e5a8f96c1..1f8c2561c8cf77e9bb695094325401c09c15f3e6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4059,14 +4059,13 @@ unsigned long wp_shared_mapping_range(struct address_space *mapping,
 #endif
 
 #ifdef CONFIG_ANON_VMA_NAME
-int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
-			  unsigned long len_in,
-			  struct anon_vma_name *anon_name);
+int prctl_set_vma(unsigned long opt, unsigned long start,
+		  unsigned long size, unsigned long arg);
 #else
-static inline int
-madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
-		      unsigned long len_in, struct anon_vma_name *anon_name) {
-	return 0;
+static inline int prctl_set_vma(unsigned long opt, unsigned long start,
+				unsigned long size, unsigned long arg)
+{
+	return -EINVAL;
 }
 #endif
 
diff --git a/kernel/sys.c b/kernel/sys.c
index adc0de0aa364aebb23999f621717a5d32599921c..247d8925daa6fc86134504042832c2164b5d8277 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2343,70 +2343,6 @@ int __weak arch_lock_shadow_stack_status(struct task_struct *t, unsigned long st
 
 #define PR_IO_FLUSHER (PF_MEMALLOC_NOIO | PF_LOCAL_THROTTLE)
 
-#ifdef CONFIG_ANON_VMA_NAME
-
-#define ANON_VMA_NAME_MAX_LEN		80
-#define ANON_VMA_NAME_INVALID_CHARS	"\\`$[]"
-
-static inline bool is_valid_name_char(char ch)
-{
-	/* printable ascii characters, excluding ANON_VMA_NAME_INVALID_CHARS */
-	return ch > 0x1f && ch < 0x7f &&
-		!strchr(ANON_VMA_NAME_INVALID_CHARS, ch);
-}
-
-static int prctl_set_vma(unsigned long opt, unsigned long addr,
-			 unsigned long size, unsigned long arg)
-{
-	struct mm_struct *mm = current->mm;
-	const char __user *uname;
-	struct anon_vma_name *anon_name = NULL;
-	int error;
-
-	switch (opt) {
-	case PR_SET_VMA_ANON_NAME:
-		uname = (const char __user *)arg;
-		if (uname) {
-			char *name, *pch;
-
-			name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN);
-			if (IS_ERR(name))
-				return PTR_ERR(name);
-
-			for (pch = name; *pch != '\0'; pch++) {
-				if (!is_valid_name_char(*pch)) {
-					kfree(name);
-					return -EINVAL;
-				}
-			}
-			/* anon_vma has its own copy */
-			anon_name = anon_vma_name_alloc(name);
-			kfree(name);
-			if (!anon_name)
-				return -ENOMEM;
-
-		}
-
-		mmap_write_lock(mm);
-		error = madvise_set_anon_name(mm, addr, size, anon_name);
-		mmap_write_unlock(mm);
-		anon_vma_name_put(anon_name);
-		break;
-	default:
-		error = -EINVAL;
-	}
-
-	return error;
-}
-
-#else /* CONFIG_ANON_VMA_NAME */
-static int prctl_set_vma(unsigned long opt, unsigned long start,
-			 unsigned long size, unsigned long arg)
-{
-	return -EINVAL;
-}
-#endif /* CONFIG_ANON_VMA_NAME */
-
 static inline unsigned long get_current_mdwe(void)
 {
 	unsigned long ret = 0;
diff --git a/mm/madvise.c b/mm/madvise.c
index ae29395b4fc7f65a449c5772b1901a90f4195885..4a8e61e2c5025726bc2ce1f323768c5b25cef2c9 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -31,6 +31,7 @@
 #include <linux/swapops.h>
 #include <linux/shmem_fs.h>
 #include <linux/mmu_notifier.h>
+#include <linux/prctl.h>
 
 #include <asm/tlb.h>
 
@@ -134,8 +135,8 @@ static int replace_anon_vma_name(struct vm_area_struct *vma,
 	return 0;
 }
 
-int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
-			  unsigned long len_in, struct anon_vma_name *anon_name)
+static int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
+		unsigned long len_in, struct anon_vma_name *anon_name)
 {
 	unsigned long end;
 	unsigned long len;
@@ -165,6 +166,60 @@ int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
 	madv_behavior.range.end = end;
 	return madvise_walk_vmas(&madv_behavior);
 }
+
+#define ANON_VMA_NAME_MAX_LEN		80
+#define ANON_VMA_NAME_INVALID_CHARS	"\\`$[]"
+
+static inline bool is_valid_name_char(char ch)
+{
+	/* printable ascii characters, excluding ANON_VMA_NAME_INVALID_CHARS */
+	return ch > 0x1f && ch < 0x7f &&
+		!strchr(ANON_VMA_NAME_INVALID_CHARS, ch);
+}
+
+int prctl_set_vma(unsigned long opt, unsigned long addr,
+		  unsigned long size, unsigned long arg)
+{
+	struct mm_struct *mm = current->mm;
+	const char __user *uname;
+	struct anon_vma_name *anon_name = NULL;
+	int error;
+
+	switch (opt) {
+	case PR_SET_VMA_ANON_NAME:
+		uname = (const char __user *)arg;
+		if (uname) {
+			char *name, *pch;
+
+			name = strndup_user(uname, ANON_VMA_NAME_MAX_LEN);
+			if (IS_ERR(name))
+				return PTR_ERR(name);
+
+			for (pch = name; *pch != '\0'; pch++) {
+				if (!is_valid_name_char(*pch)) {
+					kfree(name);
+					return -EINVAL;
+				}
+			}
+			/* anon_vma has its own copy */
+			anon_name = anon_vma_name_alloc(name);
+			kfree(name);
+			if (!anon_name)
+				return -ENOMEM;
+
+		}
+
+		mmap_write_lock(mm);
+		error = madvise_set_anon_name(mm, addr, size, anon_name);
+		mmap_write_unlock(mm);
+		anon_vma_name_put(anon_name);
+		break;
+	default:
+		error = -EINVAL;
+	}
+
+	return error;
+}
 #else /* CONFIG_ANON_VMA_NAME */
 static int replace_anon_vma_name(struct vm_area_struct *vma,
 				 struct anon_vma_name *anon_name)

-- 
2.50.0