[PATCH 1/5] mm/vma: move brk() internals to mm/vma.c

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

Now we have moved mmap_region() internals to mm/vma.c, making it available
to userland testing, it makes sense to do the same with brk().

This continues the pattern of VMA heavy lifting being done in mm/vma.c in
an environment where it can be subject to straightforward unit and
regression testing, with other VMA-adjacent files becoming wrappers around
this functionality.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
 mm/mmap.c                        | 85 +-------------------------------
 mm/vma.c                         | 82 ++++++++++++++++++++++++++++++
 mm/vma.h                         |  3 ++
 tools/testing/vma/vma_internal.h | 22 +++++++++
 4 files changed, 108 insertions(+), 84 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 16f8e8be01f8..93188ef46dae 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -111,8 +111,7 @@ static int check_brk_limits(unsigned long addr, unsigned long len)
 	return mlock_future_ok(current->mm, current->mm->def_flags, len)
 		? 0 : -EAGAIN;
 }
-static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *brkvma,
-		unsigned long addr, unsigned long request, unsigned long flags);
+
 SYSCALL_DEFINE1(brk, unsigned long, brk)
 {
 	unsigned long newbrk, oldbrk, origbrk;
@@ -1512,88 +1511,6 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	return ret;
 }
 
-/*
- * do_brk_flags() - Increase the brk vma if the flags match.
- * @vmi: The vma iterator
- * @addr: The start address
- * @len: The length of the increase
- * @vma: The vma,
- * @flags: The VMA Flags
- *
- * Extend the brk VMA from addr to addr + len.  If the VMA is NULL or the flags
- * do not match then create a new anonymous VMA.  Eventually we may be able to
- * do some brk-specific accounting here.
- */
-static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
-		unsigned long addr, unsigned long len, unsigned long flags)
-{
-	struct mm_struct *mm = current->mm;
-
-	/*
-	 * Check against address space limits by the changed size
-	 * Note: This happens *after* clearing old mappings in some code paths.
-	 */
-	flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
-	if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
-		return -ENOMEM;
-
-	if (mm->map_count > sysctl_max_map_count)
-		return -ENOMEM;
-
-	if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
-		return -ENOMEM;
-
-	/*
-	 * Expand the existing vma if possible; Note that singular lists do not
-	 * occur after forking, so the expand will only happen on new VMAs.
-	 */
-	if (vma && vma->vm_end == addr) {
-		VMG_STATE(vmg, mm, vmi, addr, addr + len, flags, PHYS_PFN(addr));
-
-		vmg.prev = vma;
-		/* vmi is positioned at prev, which this mode expects. */
-		vmg.merge_flags = VMG_FLAG_JUST_EXPAND;
-
-		if (vma_merge_new_range(&vmg))
-			goto out;
-		else if (vmg_nomem(&vmg))
-			goto unacct_fail;
-	}
-
-	if (vma)
-		vma_iter_next_range(vmi);
-	/* create a vma struct for an anonymous mapping */
-	vma = vm_area_alloc(mm);
-	if (!vma)
-		goto unacct_fail;
-
-	vma_set_anonymous(vma);
-	vma_set_range(vma, addr, addr + len, addr >> PAGE_SHIFT);
-	vm_flags_init(vma, flags);
-	vma->vm_page_prot = vm_get_page_prot(flags);
-	vma_start_write(vma);
-	if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL))
-		goto mas_store_fail;
-
-	mm->map_count++;
-	validate_mm(mm);
-	ksm_add_vma(vma);
-out:
-	perf_event_mmap(vma);
-	mm->total_vm += len >> PAGE_SHIFT;
-	mm->data_vm += len >> PAGE_SHIFT;
-	if (flags & VM_LOCKED)
-		mm->locked_vm += (len >> PAGE_SHIFT);
-	vm_flags_set(vma, VM_SOFTDIRTY);
-	return 0;
-
-mas_store_fail:
-	vm_area_free(vma);
-unacct_fail:
-	vm_unacct_memory(len >> PAGE_SHIFT);
-	return -ENOMEM;
-}
-
 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags)
 {
 	struct mm_struct *mm = current->mm;
diff --git a/mm/vma.c b/mm/vma.c
index 8e31b7e25aeb..9955b5332ca2 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -2478,3 +2478,85 @@ unsigned long __mmap_region(struct file *file, unsigned long addr,
 	vms_abort_munmap_vmas(&map.vms, &map.mas_detach);
 	return error;
 }
+
+/*
+ * do_brk_flags() - Increase the brk vma if the flags match.
+ * @vmi: The vma iterator
+ * @addr: The start address
+ * @len: The length of the increase
+ * @vma: The vma,
+ * @flags: The VMA Flags
+ *
+ * Extend the brk VMA from addr to addr + len.  If the VMA is NULL or the flags
+ * do not match then create a new anonymous VMA.  Eventually we may be able to
+ * do some brk-specific accounting here.
+ */
+int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
+		 unsigned long addr, unsigned long len, unsigned long flags)
+{
+	struct mm_struct *mm = current->mm;
+
+	/*
+	 * Check against address space limits by the changed size
+	 * Note: This happens *after* clearing old mappings in some code paths.
+	 */
+	flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
+	if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
+		return -ENOMEM;
+
+	if (mm->map_count > sysctl_max_map_count)
+		return -ENOMEM;
+
+	if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
+		return -ENOMEM;
+
+	/*
+	 * Expand the existing vma if possible; Note that singular lists do not
+	 * occur after forking, so the expand will only happen on new VMAs.
+	 */
+	if (vma && vma->vm_end == addr) {
+		VMG_STATE(vmg, mm, vmi, addr, addr + len, flags, PHYS_PFN(addr));
+
+		vmg.prev = vma;
+		/* vmi is positioned at prev, which this mode expects. */
+		vmg.merge_flags = VMG_FLAG_JUST_EXPAND;
+
+		if (vma_merge_new_range(&vmg))
+			goto out;
+		else if (vmg_nomem(&vmg))
+			goto unacct_fail;
+	}
+
+	if (vma)
+		vma_iter_next_range(vmi);
+	/* create a vma struct for an anonymous mapping */
+	vma = vm_area_alloc(mm);
+	if (!vma)
+		goto unacct_fail;
+
+	vma_set_anonymous(vma);
+	vma_set_range(vma, addr, addr + len, addr >> PAGE_SHIFT);
+	vm_flags_init(vma, flags);
+	vma->vm_page_prot = vm_get_page_prot(flags);
+	vma_start_write(vma);
+	if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL))
+		goto mas_store_fail;
+
+	mm->map_count++;
+	validate_mm(mm);
+	ksm_add_vma(vma);
+out:
+	perf_event_mmap(vma);
+	mm->total_vm += len >> PAGE_SHIFT;
+	mm->data_vm += len >> PAGE_SHIFT;
+	if (flags & VM_LOCKED)
+		mm->locked_vm += (len >> PAGE_SHIFT);
+	vm_flags_set(vma, VM_SOFTDIRTY);
+	return 0;
+
+mas_store_fail:
+	vm_area_free(vma);
+unacct_fail:
+	vm_unacct_memory(len >> PAGE_SHIFT);
+	return -ENOMEM;
+}
diff --git a/mm/vma.h b/mm/vma.h
index 388d34748674..83a15d3a8285 100644
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -247,6 +247,9 @@ unsigned long __mmap_region(struct file *file, unsigned long addr,
 		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
 		struct list_head *uf);
 
+int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *brkvma,
+		 unsigned long addr, unsigned long request, unsigned long flags);
+
 static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma)
 {
 	/*
diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
index e76ff579e1fd..7c3c15135c5b 100644
--- a/tools/testing/vma/vma_internal.h
+++ b/tools/testing/vma/vma_internal.h
@@ -39,6 +39,7 @@
 #define VM_SHARED	0x00000008
 #define VM_MAYREAD	0x00000010
 #define VM_MAYWRITE	0x00000020
+#define VM_MAYEXEC	0x00000040
 #define VM_GROWSDOWN	0x00000100
 #define VM_PFNMAP	0x00000400
 #define VM_LOCKED	0x00002000
@@ -58,6 +59,13 @@
 /* This mask represents all the VMA flag bits used by mlock */
 #define VM_LOCKED_MASK	(VM_LOCKED | VM_LOCKONFAULT)
 
+#define TASK_EXEC ((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0)
+
+#define VM_DATA_FLAGS_TSK_EXEC	(VM_READ | VM_WRITE | TASK_EXEC | \
+				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
+
+#define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_TSK_EXEC
+
 #ifdef CONFIG_64BIT
 /* VM is sealed, in vm_flags */
 #define VM_SEALED	_BITUL(63)
@@ -122,10 +130,22 @@ enum {
 	TASK_COMM_LEN = 16,
 };
 
+/*
+ * Flags for bug emulation.
+ *
+ * These occupy the top three bytes.
+ */
+enum {
+	READ_IMPLIES_EXEC =	0x0400000,
+};
+
 struct task_struct {
 	char comm[TASK_COMM_LEN];
 	pid_t pid;
 	struct mm_struct *mm;
+
+	/* Used for emulating ABI behavior of previous Linux versions: */
+	unsigned int			personality;
 };
 
 struct task_struct *get_current(void);
@@ -186,6 +206,8 @@ struct mm_struct {
 	unsigned long data_vm;	   /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
 	unsigned long exec_vm;	   /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
 	unsigned long stack_vm;	   /* VM_STACK */
+
+	unsigned long def_flags;
 };
 
 struct vma_lock {
-- 
2.47.1