[PATCH 1/5] mm/vma: move brk() internals to mm/vma.c
From: Lorenzo Stoakes
Date: Tue Dec 03 2024 - 13:06:06 EST
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@xxxxxxxxxx>
---
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