From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/mm/mremap.c | 528 +++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 files changed, 461 insertions(+), 67 deletions(-)
diff --git a/kernel/mm/mremap.c b/kernel/mm/mremap.c
index 16630b5..b1263e9 100644
--- a/kernel/mm/mremap.c
+++ b/kernel/mm/mremap.c
@@ -30,12 +30,11 @@
#include "internal.h"
-static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
+static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
- pmd_t *pmd;
pgd = pgd_offset(mm, addr);
if (pgd_none_or_clear_bad(pgd))
@@ -49,6 +48,18 @@
if (pud_none_or_clear_bad(pud))
return NULL;
+ return pud;
+}
+
+static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
+{
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pud = get_old_pud(mm, addr);
+ if (!pud)
+ return NULL;
+
pmd = pmd_offset(pud, addr);
if (pmd_none(*pmd))
return NULL;
@@ -56,19 +67,27 @@
return pmd;
}
-static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
+static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr)
{
pgd_t *pgd;
p4d_t *p4d;
- pud_t *pud;
- pmd_t *pmd;
pgd = pgd_offset(mm, addr);
p4d = p4d_alloc(mm, pgd, addr);
if (!p4d)
return NULL;
- pud = pud_alloc(mm, p4d, addr);
+
+ return pud_alloc(mm, p4d, addr);
+}
+
+static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pud = alloc_new_pud(mm, vma, addr);
if (!pud)
return NULL;
@@ -133,7 +152,7 @@
* such races:
*
* - During exec() shift_arg_pages(), we use a specially tagged vma
- * which rmap call sites look for using is_vma_temporary_stack().
+ * which rmap call sites look for using vma_is_temporary_stack().
*
* - During mremap(), new_vma is often known to be placed after vma
* in rmap traversal order. This ensures rmap will always observe
@@ -146,7 +165,7 @@
/*
* We don't have to worry about the ordering of src and dst
- * pte locks because exclusive mmap_sem prevents deadlock.
+ * pte locks because exclusive mmap_lock prevents deadlock.
*/
old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
new_pte = pte_offset_map(new_pmd, new_addr);
@@ -191,63 +210,327 @@
drop_rmap_locks(vma);
}
+#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
+static inline bool trylock_vma_ref_count(struct vm_area_struct *vma)
+{
+ /*
+ * If we have the only reference, swap the refcount to -1. This
+ * will prevent other concurrent references by get_vma() for SPFs.
+ */
+ return atomic_cmpxchg(&vma->vm_ref_count, 1, -1) == 1;
+}
+
+/*
+ * Restore the VMA reference count to 1 after a fast mremap.
+ */
+static inline void unlock_vma_ref_count(struct vm_area_struct *vma)
+{
+ /*
+ * This should only be called after a corresponding,
+ * successful trylock_vma_ref_count().
+ */
+ VM_BUG_ON_VMA(atomic_cmpxchg(&vma->vm_ref_count, -1, 1) != -1,
+ vma);
+}
+#else /* !CONFIG_SPECULATIVE_PAGE_FAULT */
+static inline bool trylock_vma_ref_count(struct vm_area_struct *vma)
+{
+ return true;
+}
+static inline void unlock_vma_ref_count(struct vm_area_struct *vma)
+{
+}
+#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */
+
+#ifdef CONFIG_HAVE_MOVE_PMD
+static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
+ unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
+{
+ spinlock_t *old_ptl, *new_ptl;
+ struct mm_struct *mm = vma->vm_mm;
+ pmd_t pmd;
+
+ /*
+ * The destination pmd shouldn't be established, free_pgtables()
+ * should have released it.
+ *
+ * However, there's a case during execve() where we use mremap
+ * to move the initial stack, and in that case the target area
+ * may overlap the source area (always moving down).
+ *
+ * If everything is PMD-aligned, that works fine, as moving
+ * each pmd down will clear the source pmd. But if we first
+ * have a few 4kB-only pages that get moved down, and then
+ * hit the "now the rest is PMD-aligned, let's do everything
+ * one pmd at a time", we will still have the old (now empty
+ * of any 4kB pages, but still there) PMD in the page table
+ * tree.
+ *
+ * Warn on it once - because we really should try to figure
+ * out how to do this better - but then say "I won't move
+ * this pmd".
+ *
+ * One alternative might be to just unmap the target pmd at
+ * this point, and verify that it really is empty. We'll see.
+ */
+ if (WARN_ON_ONCE(!pmd_none(*new_pmd)))
+ return false;
+
+ /*
+ * We hold both exclusive mmap_lock and rmap_lock at this point and
+ * cannot block. If we cannot immediately take exclusive ownership
+ * of the VMA fallback to the move_ptes().
+ */
+ if (!trylock_vma_ref_count(vma))
+ return false;
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * ptlocks because exclusive mmap_lock prevents deadlock.
+ */
+ old_ptl = pmd_lock(vma->vm_mm, old_pmd);
+ new_ptl = pmd_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+
+ /* Clear the pmd */
+ pmd = *old_pmd;
+ pmd_clear(old_pmd);
+
+ VM_BUG_ON(!pmd_none(*new_pmd));
+
+ /* Set the new pmd */
+ set_pmd_at(mm, new_addr, new_pmd, pmd);
+ flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ spin_unlock(old_ptl);
+
+ unlock_vma_ref_count(vma);
+ return true;
+}
+#else
+static inline bool move_normal_pmd(struct vm_area_struct *vma,
+ unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd,
+ pmd_t *new_pmd)
+{
+ return false;
+}
+#endif
+
+#ifdef CONFIG_HAVE_MOVE_PUD
+static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
+ unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
+{
+ spinlock_t *old_ptl, *new_ptl;
+ struct mm_struct *mm = vma->vm_mm;
+ pud_t pud;
+
+ /*
+ * The destination pud shouldn't be established, free_pgtables()
+ * should have released it.
+ */
+ if (WARN_ON_ONCE(!pud_none(*new_pud)))
+ return false;
+
+ /*
+ * We hold both exclusive mmap_lock and rmap_lock at this point and
+ * cannot block. If we cannot immediately take exclusive ownership
+ * of the VMA fallback to the move_ptes().
+ */
+ if (!trylock_vma_ref_count(vma))
+ return false;
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * ptlocks because exclusive mmap_lock prevents deadlock.
+ */
+ old_ptl = pud_lock(vma->vm_mm, old_pud);
+ new_ptl = pud_lockptr(mm, new_pud);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+
+ /* Clear the pud */
+ pud = *old_pud;
+ pud_clear(old_pud);
+
+ VM_BUG_ON(!pud_none(*new_pud));
+
+ /* Set the new pud */
+ set_pud_at(mm, new_addr, new_pud, pud);
+ flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ spin_unlock(old_ptl);
+
+ unlock_vma_ref_count(vma);
+ return true;
+}
+#else
+static inline bool move_normal_pud(struct vm_area_struct *vma,
+ unsigned long old_addr, unsigned long new_addr, pud_t *old_pud,
+ pud_t *new_pud)
+{
+ return false;
+}
+#endif
+
+enum pgt_entry {
+ NORMAL_PMD,
+ HPAGE_PMD,
+ NORMAL_PUD,
+};
+
+/*
+ * Returns an extent of the corresponding size for the pgt_entry specified if
+ * valid. Else returns a smaller extent bounded by the end of the source and
+ * destination pgt_entry.
+ */
+static __always_inline unsigned long get_extent(enum pgt_entry entry,
+ unsigned long old_addr, unsigned long old_end,
+ unsigned long new_addr)
+{
+ unsigned long next, extent, mask, size;
+
+ switch (entry) {
+ case HPAGE_PMD:
+ case NORMAL_PMD:
+ mask = PMD_MASK;
+ size = PMD_SIZE;
+ break;
+ case NORMAL_PUD:
+ mask = PUD_MASK;
+ size = PUD_SIZE;
+ break;
+ default:
+ BUILD_BUG();
+ break;
+ }
+
+ next = (old_addr + size) & mask;
+ /* even if next overflowed, extent below will be ok */
+ extent = next - old_addr;
+ if (extent > old_end - old_addr)
+ extent = old_end - old_addr;
+ next = (new_addr + size) & mask;
+ if (extent > next - new_addr)
+ extent = next - new_addr;
+ return extent;
+}
+
+/*
+ * Attempts to speedup the move by moving entry at the level corresponding to
+ * pgt_entry. Returns true if the move was successful, else false.
+ */
+static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
+ unsigned long old_addr, unsigned long new_addr,
+ void *old_entry, void *new_entry, bool need_rmap_locks)
+{
+ bool moved = false;
+
+ /* See comment in move_ptes() */
+ if (need_rmap_locks)
+ take_rmap_locks(vma);
+
+ switch (entry) {
+ case NORMAL_PMD:
+ moved = move_normal_pmd(vma, old_addr, new_addr, old_entry,
+ new_entry);
+ break;
+ case NORMAL_PUD:
+ moved = move_normal_pud(vma, old_addr, new_addr, old_entry,
+ new_entry);
+ break;
+ case HPAGE_PMD:
+ moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+ move_huge_pmd(vma, old_addr, new_addr, old_entry,
+ new_entry);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+
+ if (need_rmap_locks)
+ drop_rmap_locks(vma);
+
+ return moved;
+}
+
unsigned long move_page_tables(struct vm_area_struct *vma,
unsigned long old_addr, struct vm_area_struct *new_vma,
unsigned long new_addr, unsigned long len,
bool need_rmap_locks)
{
- unsigned long extent, next, old_end;
+ unsigned long extent, old_end;
+ struct mmu_notifier_range range;
pmd_t *old_pmd, *new_pmd;
- unsigned long mmun_start; /* For mmu_notifiers */
- unsigned long mmun_end; /* For mmu_notifiers */
+
+ if (!len)
+ return 0;
old_end = old_addr + len;
flush_cache_range(vma, old_addr, old_end);
- mmun_start = old_addr;
- mmun_end = old_end;
- mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
+ mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm,
+ old_addr, old_end);
+ mmu_notifier_invalidate_range_start(&range);
for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
cond_resched();
- next = (old_addr + PMD_SIZE) & PMD_MASK;
- /* even if next overflowed, extent below will be ok */
- extent = next - old_addr;
- if (extent > old_end - old_addr)
- extent = old_end - old_addr;
+ /*
+ * If extent is PUD-sized try to speed up the move by moving at the
+ * PUD level if possible.
+ */
+ extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
+ if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) {
+ pud_t *old_pud, *new_pud;
+
+ old_pud = get_old_pud(vma->vm_mm, old_addr);
+ if (!old_pud)
+ continue;
+ new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
+ if (!new_pud)
+ break;
+ if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
+ old_pud, new_pud, true))
+ continue;
+ }
+
+ extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
old_pmd = get_old_pmd(vma->vm_mm, old_addr);
if (!old_pmd)
continue;
new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
if (!new_pmd)
break;
- if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) {
- if (extent == HPAGE_PMD_SIZE) {
- bool moved;
- /* See comment in move_ptes() */
- if (need_rmap_locks)
- take_rmap_locks(vma);
- moved = move_huge_pmd(vma, old_addr, new_addr,
- old_end, old_pmd, new_pmd);
- if (need_rmap_locks)
- drop_rmap_locks(vma);
- if (moved)
- continue;
- }
+ if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) ||
+ pmd_devmap(*old_pmd)) {
+ if (extent == HPAGE_PMD_SIZE &&
+ move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr,
+ old_pmd, new_pmd, need_rmap_locks))
+ continue;
split_huge_pmd(vma, old_pmd, old_addr);
if (pmd_trans_unstable(old_pmd))
continue;
+ } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) &&
+ extent == PMD_SIZE) {
+ /*
+ * If the extent is PMD-sized, try to speed the move by
+ * moving at the PMD level if possible.
+ */
+ if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr,
+ old_pmd, new_pmd, true))
+ continue;
}
- if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr))
+
+ if (pte_alloc(new_vma->vm_mm, new_pmd))
break;
- next = (new_addr + PMD_SIZE) & PMD_MASK;
- if (extent > next - new_addr)
- extent = next - new_addr;
move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
new_pmd, new_addr, need_rmap_locks);
}
- mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
+ mmu_notifier_invalidate_range_end(&range);
return len + old_addr - old_end; /* how much done */
}
@@ -255,8 +538,8 @@
static unsigned long move_vma(struct vm_area_struct *vma,
unsigned long old_addr, unsigned long old_len,
unsigned long new_len, unsigned long new_addr,
- bool *locked, struct vm_userfaultfd_ctx *uf,
- struct list_head *uf_unmap)
+ bool *locked, unsigned long flags,
+ struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap)
{
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *new_vma;
@@ -294,6 +577,14 @@
if (!new_vma)
return -ENOMEM;
+ /* new_vma is returned protected by copy_vma, to prevent speculative
+ * page fault to be done in the destination area before we move the pte.
+ * Now, we must also protect the source VMA since we don't want pages
+ * to be mapped in our back while we are copying the PTEs.
+ */
+ if (vma != new_vma)
+ vm_write_begin(vma);
+
moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
need_rmap_locks);
if (moved_len < old_len) {
@@ -310,6 +601,8 @@
*/
move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
true);
+ if (vma != new_vma)
+ vm_write_end(vma);
vma = new_vma;
old_len = new_len;
old_addr = new_addr;
@@ -318,7 +611,10 @@
mremap_userfaultfd_prep(new_vma, uf);
arch_remap(mm, old_addr, old_addr + old_len,
new_addr, new_addr + new_len);
+ if (vma != new_vma)
+ vm_write_end(vma);
}
+ vm_write_end(new_vma);
/* Conceal VM_ACCOUNT so old reservation is not undone */
if (vm_flags & VM_ACCOUNT) {
@@ -345,11 +641,43 @@
if (unlikely(vma->vm_flags & VM_PFNMAP))
untrack_pfn_moved(vma);
+ if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) {
+ if (vm_flags & VM_ACCOUNT) {
+ /* Always put back VM_ACCOUNT since we won't unmap */
+ vma->vm_flags |= VM_ACCOUNT;
+
+ vm_acct_memory(new_len >> PAGE_SHIFT);
+ }
+
+ /*
+ * VMAs can actually be merged back together in copy_vma
+ * calling merge_vma. This can happen with anonymous vmas
+ * which have not yet been faulted, so if we were to consider
+ * this VMA split we'll end up adding VM_ACCOUNT on the
+ * next VMA, which is completely unrelated if this VMA
+ * was re-merged.
+ */
+ if (split && new_vma == vma)
+ split = 0;
+
+ /* We always clear VM_LOCKED[ONFAULT] on the old vma */
+ vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+
+ /* Because we won't unmap we don't need to touch locked_vm */
+ goto out;
+ }
+
if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
/* OOM: unable to split vma, just get accounts right */
vm_unacct_memory(excess >> PAGE_SHIFT);
excess = 0;
}
+
+ if (vm_flags & VM_LOCKED) {
+ mm->locked_vm += new_len >> PAGE_SHIFT;
+ *locked = true;
+ }
+out:
mm->hiwater_vm = hiwater_vm;
/* Restore VM_ACCOUNT if one or two pieces of vma left */
@@ -359,16 +687,12 @@
vma->vm_next->vm_flags |= VM_ACCOUNT;
}
- if (vm_flags & VM_LOCKED) {
- mm->locked_vm += new_len >> PAGE_SHIFT;
- *locked = true;
- }
-
return new_addr;
}
static struct vm_area_struct *vma_to_resize(unsigned long addr,
- unsigned long old_len, unsigned long new_len, unsigned long *p)
+ unsigned long old_len, unsigned long new_len, unsigned long flags,
+ unsigned long *p)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = find_vma(mm, addr);
@@ -389,6 +713,10 @@
pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
return ERR_PTR(-EINVAL);
}
+
+ if ((flags & MREMAP_DONTUNMAP) &&
+ (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
+ return ERR_PTR(-EINVAL);
if (is_vm_hugetlb_page(vma))
return ERR_PTR(-EINVAL);
@@ -434,7 +762,7 @@
static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
unsigned long new_addr, unsigned long new_len, bool *locked,
- struct vm_userfaultfd_ctx *uf,
+ unsigned long flags, struct vm_userfaultfd_ctx *uf,
struct list_head *uf_unmap_early,
struct list_head *uf_unmap)
{
@@ -442,7 +770,7 @@
struct vm_area_struct *vma;
unsigned long ret = -EINVAL;
unsigned long charged = 0;
- unsigned long map_flags;
+ unsigned long map_flags = 0;
if (offset_in_page(new_addr))
goto out;
@@ -454,9 +782,28 @@
if (addr + old_len > new_addr && new_addr + new_len > addr)
goto out;
- ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
- if (ret)
- goto out;
+ /*
+ * move_vma() need us to stay 4 maps below the threshold, otherwise
+ * it will bail out at the very beginning.
+ * That is a problem if we have already unmaped the regions here
+ * (new_addr, and old_addr), because userspace will not know the
+ * state of the vma's after it gets -ENOMEM.
+ * So, to avoid such scenario we can pre-compute if the whole
+ * operation has high chances to success map-wise.
+ * Worst-scenario case is when both vma's (new_addr and old_addr) get
+ * split in 3 before unmaping it.
+ * That means 2 more maps (1 for each) to the ones we already hold.
+ * Check whether current map count plus 2 still leads us to 4 maps below
+ * the threshold, otherwise return -ENOMEM here to be more safe.
+ */
+ if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
+ return -ENOMEM;
+
+ if (flags & MREMAP_FIXED) {
+ ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
+ if (ret)
+ goto out;
+ }
if (old_len >= new_len) {
ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
@@ -465,26 +812,41 @@
old_len = new_len;
}
- vma = vma_to_resize(addr, old_len, new_len, &charged);
+ vma = vma_to_resize(addr, old_len, new_len, flags, &charged);
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto out;
}
- map_flags = MAP_FIXED;
+ /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
+ if (flags & MREMAP_DONTUNMAP &&
+ !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ if (flags & MREMAP_FIXED)
+ map_flags |= MAP_FIXED;
+
if (vma->vm_flags & VM_MAYSHARE)
map_flags |= MAP_SHARED;
ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
((addr - vma->vm_start) >> PAGE_SHIFT),
map_flags);
- if (offset_in_page(ret))
+ if (IS_ERR_VALUE(ret))
goto out1;
- ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, uf,
+ /* We got a new mapping */
+ if (!(flags & MREMAP_FIXED))
+ new_addr = ret;
+
+ ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf,
uf_unmap);
+
if (!(offset_in_page(ret)))
goto out;
+
out1:
vm_unacct_memory(charged);
@@ -521,17 +883,37 @@
unsigned long ret = -EINVAL;
unsigned long charged = 0;
bool locked = false;
+ bool downgraded = false;
struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
LIST_HEAD(uf_unmap_early);
LIST_HEAD(uf_unmap);
+ /*
+ * There is a deliberate asymmetry here: we strip the pointer tag
+ * from the old address but leave the new address alone. This is
+ * for consistency with mmap(), where we prevent the creation of
+ * aliasing mappings in userspace by leaving the tag bits of the
+ * mapping address intact. A non-zero tag will cause the subsequent
+ * range checks to reject the address as invalid.
+ *
+ * See Documentation/arm64/tagged-address-abi.rst for more information.
+ */
addr = untagged_addr(addr);
- if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
+ if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
return ret;
if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
return ret;
+
+ /*
+ * MREMAP_DONTUNMAP is always a move and it does not allow resizing
+ * in the process.
+ */
+ if (flags & MREMAP_DONTUNMAP &&
+ (!(flags & MREMAP_MAYMOVE) || old_len != new_len))
+ return ret;
+
if (offset_in_page(addr))
return ret;
@@ -547,24 +929,33 @@
if (!new_len)
return ret;
- if (down_write_killable(¤t->mm->mmap_sem))
+ if (mmap_write_lock_killable(current->mm))
return -EINTR;
- if (flags & MREMAP_FIXED) {
+ if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) {
ret = mremap_to(addr, old_len, new_addr, new_len,
- &locked, &uf, &uf_unmap_early, &uf_unmap);
+ &locked, flags, &uf, &uf_unmap_early,
+ &uf_unmap);
goto out;
}
/*
* Always allow a shrinking remap: that just unmaps
* the unnecessary pages..
- * do_munmap does all the needed commit accounting
+ * __do_munmap does all the needed commit accounting, and
+ * downgrades mmap_lock to read if so directed.
*/
if (old_len >= new_len) {
- ret = do_munmap(mm, addr+new_len, old_len - new_len, &uf_unmap);
- if (ret && old_len != new_len)
+ int retval;
+
+ retval = __do_munmap(mm, addr+new_len, old_len - new_len,
+ &uf_unmap, true);
+ if (retval < 0 && old_len != new_len) {
+ ret = retval;
goto out;
+ /* Returning 1 indicates mmap_lock is downgraded to read. */
+ } else if (retval == 1)
+ downgraded = true;
ret = addr;
goto out;
}
@@ -572,7 +963,7 @@
/*
* Ok, we need to grow..
*/
- vma = vma_to_resize(addr, old_len, new_len, &charged);
+ vma = vma_to_resize(addr, old_len, new_len, flags, &charged);
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto out;
@@ -616,24 +1007,27 @@
vma->vm_pgoff +
((addr - vma->vm_start) >> PAGE_SHIFT),
map_flags);
- if (offset_in_page(new_addr)) {
+ if (IS_ERR_VALUE(new_addr)) {
ret = new_addr;
goto out;
}
ret = move_vma(vma, addr, old_len, new_len, new_addr,
- &locked, &uf, &uf_unmap);
+ &locked, flags, &uf, &uf_unmap);
}
out:
if (offset_in_page(ret)) {
vm_unacct_memory(charged);
- locked = 0;
+ locked = false;
}
- up_write(¤t->mm->mmap_sem);
+ if (downgraded)
+ mmap_read_unlock(current->mm);
+ else
+ mmap_write_unlock(current->mm);
if (locked && new_len > old_len)
mm_populate(new_addr + old_len, new_len - old_len);
userfaultfd_unmap_complete(mm, &uf_unmap_early);
- mremap_userfaultfd_complete(&uf, addr, new_addr, old_len);
+ mremap_userfaultfd_complete(&uf, addr, ret, old_len);
userfaultfd_unmap_complete(mm, &uf_unmap);
return ret;
}
--
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