Quelle  vma_init.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-or-later

/*
 * Functions for initialisaing, allocating, freeing and duplicating VMAs. Shared
 * between CONFIG_MMU and non-CONFIG_MMU kernel configurations.
 */

#include "vma_internal.h"
#include "vma.h"

/* SLAB cache for vm_area_struct structures */
static struct kmem_cache *vm_area_cachep;

void __init vma_state_init(void)
{
 struct kmem_cache_args args = {
  .use_freeptr_offset = true,
  .freeptr_offset = offsetof(struct vm_area_struct, vm_freeptr),
 };

 vm_area_cachep = kmem_cache_create("vm_area_struct",
   sizeof(struct vm_area_struct), &args,
   SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
   SLAB_ACCOUNT);
}

struct vm_area_struct *vm_area_alloc(struct mm_struct *mm)
{
 struct vm_area_struct *vma;

 vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 if (!vma)
  return NULL;

 vma_init(vma, mm);

 return vma;
}

static void vm_area_init_from(const struct vm_area_struct *src,
         struct vm_area_struct *dest)
{
 dest->vm_mm = src->vm_mm;
 dest->vm_ops = src->vm_ops;
 dest->vm_start = src->vm_start;
 dest->vm_end = src->vm_end;
 dest->anon_vma = src->anon_vma;
 dest->vm_pgoff = src->vm_pgoff;
 dest->vm_file = src->vm_file;
 dest->vm_private_data = src->vm_private_data;
 vm_flags_init(dest, src->vm_flags);
 memcpy(&dest->vm_page_prot, &src->vm_page_prot,
        sizeof(dest->vm_page_prot));
 /*
 * src->shared.rb may be modified concurrently when called from
 * dup_mmap(), but the clone will reinitialize it.
 */
 data_race(memcpy(&dest->shared, &src->shared, sizeof(dest->shared)));
 memcpy(&dest->vm_userfaultfd_ctx, &src->vm_userfaultfd_ctx,
        sizeof(dest->vm_userfaultfd_ctx));
#ifdef CONFIG_ANON_VMA_NAME
 dest->anon_name = src->anon_name;
#endif
#ifdef CONFIG_SWAP
 memcpy(&dest->swap_readahead_info, &src->swap_readahead_info,
        sizeof(dest->swap_readahead_info));
#endif
#ifndef CONFIG_MMU
 dest->vm_region = src->vm_region;
#endif
#ifdef CONFIG_NUMA
 dest->vm_policy = src->vm_policy;
#endif
#ifdef __HAVE_PFNMAP_TRACKING
 dest->pfnmap_track_ctx = NULL;
#endif
}

#ifdef __HAVE_PFNMAP_TRACKING
static inline int vma_pfnmap_track_ctx_dup(struct vm_area_struct *orig,
  struct vm_area_struct *new)
{
 struct pfnmap_track_ctx *ctx = orig->pfnmap_track_ctx;

 if (likely(!ctx))
  return 0;

 /*
 * We don't expect to ever hit this. If ever required, we would have
 * to duplicate the tracking.
 */
 if (unlikely(kref_read(&ctx->kref) >= REFCOUNT_MAX))
  return -ENOMEM;
 kref_get(&ctx->kref);
 new->pfnmap_track_ctx = ctx;
 return 0;
}

static inline void vma_pfnmap_track_ctx_release(struct vm_area_struct *vma)
{
 struct pfnmap_track_ctx *ctx = vma->pfnmap_track_ctx;

 if (likely(!ctx))
  return;

 kref_put(&ctx->kref, pfnmap_track_ctx_release);
 vma->pfnmap_track_ctx = NULL;
}
#else
static inline int vma_pfnmap_track_ctx_dup(struct vm_area_struct *orig,
  struct vm_area_struct *new)
{
 return 0;
}
static inline void vma_pfnmap_track_ctx_release(struct vm_area_struct *vma)
{
}
#endif

struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
{
 struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);

 if (!new)
  return NULL;

 ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
 ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
 vm_area_init_from(orig, new);

 if (vma_pfnmap_track_ctx_dup(orig, new)) {
  kmem_cache_free(vm_area_cachep, new);
  return NULL;
 }
 vma_lock_init(new, true);
 INIT_LIST_HEAD(&new->anon_vma_chain);
 vma_numab_state_init(new);
 dup_anon_vma_name(orig, new);

 return new;
}

void vm_area_free(struct vm_area_struct *vma)
{
 /* The vma should be detached while being destroyed. */
 vma_assert_detached(vma);
 vma_numab_state_free(vma);
 free_anon_vma_name(vma);
 vma_pfnmap_track_ctx_release(vma);
 kmem_cache_free(vm_area_cachep, vma);
}