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-rw-r--r--mm/iov_iter.c743
1 files changed, 743 insertions, 0 deletions
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
new file mode 100644
index 00000000000..7b5dbd1517b
--- /dev/null
+++ b/mm/iov_iter.c
@@ -0,0 +1,743 @@
+#include <linux/export.h>
+#include <linux/uio.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t skip, copy, left, wanted;
+ const struct iovec *iov;
+ char __user *buf;
+ void *kaddr, *from;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ wanted = bytes;
+ iov = i->iov;
+ skip = i->iov_offset;
+ buf = iov->iov_base + skip;
+ copy = min(bytes, iov->iov_len - skip);
+
+ if (!fault_in_pages_writeable(buf, copy)) {
+ kaddr = kmap_atomic(page);
+ from = kaddr + offset;
+
+ /* first chunk, usually the only one */
+ left = __copy_to_user_inatomic(buf, from, copy);
+ copy -= left;
+ skip += copy;
+ from += copy;
+ bytes -= copy;
+
+ while (unlikely(!left && bytes)) {
+ iov++;
+ buf = iov->iov_base;
+ copy = min(bytes, iov->iov_len);
+ left = __copy_to_user_inatomic(buf, from, copy);
+ copy -= left;
+ skip = copy;
+ from += copy;
+ bytes -= copy;
+ }
+ if (likely(!bytes)) {
+ kunmap_atomic(kaddr);
+ goto done;
+ }
+ offset = from - kaddr;
+ buf += copy;
+ kunmap_atomic(kaddr);
+ copy = min(bytes, iov->iov_len - skip);
+ }
+ /* Too bad - revert to non-atomic kmap */
+ kaddr = kmap(page);
+ from = kaddr + offset;
+ left = __copy_to_user(buf, from, copy);
+ copy -= left;
+ skip += copy;
+ from += copy;
+ bytes -= copy;
+ while (unlikely(!left && bytes)) {
+ iov++;
+ buf = iov->iov_base;
+ copy = min(bytes, iov->iov_len);
+ left = __copy_to_user(buf, from, copy);
+ copy -= left;
+ skip = copy;
+ from += copy;
+ bytes -= copy;
+ }
+ kunmap(page);
+done:
+ if (skip == iov->iov_len) {
+ iov++;
+ skip = 0;
+ }
+ i->count -= wanted - bytes;
+ i->nr_segs -= iov - i->iov;
+ i->iov = iov;
+ i->iov_offset = skip;
+ return wanted - bytes;
+}
+
+static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t skip, copy, left, wanted;
+ const struct iovec *iov;
+ char __user *buf;
+ void *kaddr, *to;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ wanted = bytes;
+ iov = i->iov;
+ skip = i->iov_offset;
+ buf = iov->iov_base + skip;
+ copy = min(bytes, iov->iov_len - skip);
+
+ if (!fault_in_pages_readable(buf, copy)) {
+ kaddr = kmap_atomic(page);
+ to = kaddr + offset;
+
+ /* first chunk, usually the only one */
+ left = __copy_from_user_inatomic(to, buf, copy);
+ copy -= left;
+ skip += copy;
+ to += copy;
+ bytes -= copy;
+
+ while (unlikely(!left && bytes)) {
+ iov++;
+ buf = iov->iov_base;
+ copy = min(bytes, iov->iov_len);
+ left = __copy_from_user_inatomic(to, buf, copy);
+ copy -= left;
+ skip = copy;
+ to += copy;
+ bytes -= copy;
+ }
+ if (likely(!bytes)) {
+ kunmap_atomic(kaddr);
+ goto done;
+ }
+ offset = to - kaddr;
+ buf += copy;
+ kunmap_atomic(kaddr);
+ copy = min(bytes, iov->iov_len - skip);
+ }
+ /* Too bad - revert to non-atomic kmap */
+ kaddr = kmap(page);
+ to = kaddr + offset;
+ left = __copy_from_user(to, buf, copy);
+ copy -= left;
+ skip += copy;
+ to += copy;
+ bytes -= copy;
+ while (unlikely(!left && bytes)) {
+ iov++;
+ buf = iov->iov_base;
+ copy = min(bytes, iov->iov_len);
+ left = __copy_from_user(to, buf, copy);
+ copy -= left;
+ skip = copy;
+ to += copy;
+ bytes -= copy;
+ }
+ kunmap(page);
+done:
+ if (skip == iov->iov_len) {
+ iov++;
+ skip = 0;
+ }
+ i->count -= wanted - bytes;
+ i->nr_segs -= iov - i->iov;
+ i->iov = iov;
+ i->iov_offset = skip;
+ return wanted - bytes;
+}
+
+static size_t __iovec_copy_from_user_inatomic(char *vaddr,
+ const struct iovec *iov, size_t base, size_t bytes)
+{
+ size_t copied = 0, left = 0;
+
+ while (bytes) {
+ char __user *buf = iov->iov_base + base;
+ int copy = min(bytes, iov->iov_len - base);
+
+ base = 0;
+ left = __copy_from_user_inatomic(vaddr, buf, copy);
+ copied += copy;
+ bytes -= copy;
+ vaddr += copy;
+ iov++;
+
+ if (unlikely(left))
+ break;
+ }
+ return copied - left;
+}
+
+/*
+ * Copy as much as we can into the page and return the number of bytes which
+ * were successfully copied. If a fault is encountered then return the number of
+ * bytes which were copied.
+ */
+static size_t copy_from_user_atomic_iovec(struct page *page,
+ struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+ char *kaddr;
+ size_t copied;
+
+ kaddr = kmap_atomic(page);
+ if (likely(i->nr_segs == 1)) {
+ int left;
+ char __user *buf = i->iov->iov_base + i->iov_offset;
+ left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
+ copied = bytes - left;
+ } else {
+ copied = __iovec_copy_from_user_inatomic(kaddr + offset,
+ i->iov, i->iov_offset, bytes);
+ }
+ kunmap_atomic(kaddr);
+
+ return copied;
+}
+
+static void advance_iovec(struct iov_iter *i, size_t bytes)
+{
+ BUG_ON(i->count < bytes);
+
+ if (likely(i->nr_segs == 1)) {
+ i->iov_offset += bytes;
+ i->count -= bytes;
+ } else {
+ const struct iovec *iov = i->iov;
+ size_t base = i->iov_offset;
+ unsigned long nr_segs = i->nr_segs;
+
+ /*
+ * The !iov->iov_len check ensures we skip over unlikely
+ * zero-length segments (without overruning the iovec).
+ */
+ while (bytes || unlikely(i->count && !iov->iov_len)) {
+ int copy;
+
+ copy = min(bytes, iov->iov_len - base);
+ BUG_ON(!i->count || i->count < copy);
+ i->count -= copy;
+ bytes -= copy;
+ base += copy;
+ if (iov->iov_len == base) {
+ iov++;
+ nr_segs--;
+ base = 0;
+ }
+ }
+ i->iov = iov;
+ i->iov_offset = base;
+ i->nr_segs = nr_segs;
+ }
+}
+
+/*
+ * Fault in the first iovec of the given iov_iter, to a maximum length
+ * of bytes. Returns 0 on success, or non-zero if the memory could not be
+ * accessed (ie. because it is an invalid address).
+ *
+ * writev-intensive code may want this to prefault several iovecs -- that
+ * would be possible (callers must not rely on the fact that _only_ the
+ * first iovec will be faulted with the current implementation).
+ */
+int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
+{
+ if (!(i->type & ITER_BVEC)) {
+ char __user *buf = i->iov->iov_base + i->iov_offset;
+ bytes = min(bytes, i->iov->iov_len - i->iov_offset);
+ return fault_in_pages_readable(buf, bytes);
+ }
+ return 0;
+}
+EXPORT_SYMBOL(iov_iter_fault_in_readable);
+
+static unsigned long alignment_iovec(const struct iov_iter *i)
+{
+ const struct iovec *iov = i->iov;
+ unsigned long res;
+ size_t size = i->count;
+ size_t n;
+
+ if (!size)
+ return 0;
+
+ res = (unsigned long)iov->iov_base + i->iov_offset;
+ n = iov->iov_len - i->iov_offset;
+ if (n >= size)
+ return res | size;
+ size -= n;
+ res |= n;
+ while (size > (++iov)->iov_len) {
+ res |= (unsigned long)iov->iov_base | iov->iov_len;
+ size -= iov->iov_len;
+ }
+ res |= (unsigned long)iov->iov_base | size;
+ return res;
+}
+
+void iov_iter_init(struct iov_iter *i, int direction,
+ const struct iovec *iov, unsigned long nr_segs,
+ size_t count)
+{
+ /* It will get better. Eventually... */
+ if (segment_eq(get_fs(), KERNEL_DS))
+ direction |= ITER_KVEC;
+ i->type = direction;
+ i->iov = iov;
+ i->nr_segs = nr_segs;
+ i->iov_offset = 0;
+ i->count = count;
+}
+EXPORT_SYMBOL(iov_iter_init);
+
+static ssize_t get_pages_iovec(struct iov_iter *i,
+ struct page **pages, size_t maxsize,
+ size_t *start)
+{
+ size_t offset = i->iov_offset;
+ const struct iovec *iov = i->iov;
+ size_t len;
+ unsigned long addr;
+ int n;
+ int res;
+
+ len = iov->iov_len - offset;
+ if (len > i->count)
+ len = i->count;
+ if (len > maxsize)
+ len = maxsize;
+ addr = (unsigned long)iov->iov_base + offset;
+ len += *start = addr & (PAGE_SIZE - 1);
+ addr &= ~(PAGE_SIZE - 1);
+ n = (len + PAGE_SIZE - 1) / PAGE_SIZE;
+ res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, pages);
+ if (unlikely(res < 0))
+ return res;
+ return (res == n ? len : res * PAGE_SIZE) - *start;
+}
+
+static ssize_t get_pages_alloc_iovec(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ size_t *start)
+{
+ size_t offset = i->iov_offset;
+ const struct iovec *iov = i->iov;
+ size_t len;
+ unsigned long addr;
+ void *p;
+ int n;
+ int res;
+
+ len = iov->iov_len - offset;
+ if (len > i->count)
+ len = i->count;
+ if (len > maxsize)
+ len = maxsize;
+ addr = (unsigned long)iov->iov_base + offset;
+ len += *start = addr & (PAGE_SIZE - 1);
+ addr &= ~(PAGE_SIZE - 1);
+ n = (len + PAGE_SIZE - 1) / PAGE_SIZE;
+
+ p = kmalloc(n * sizeof(struct page *), GFP_KERNEL);
+ if (!p)
+ p = vmalloc(n * sizeof(struct page *));
+ if (!p)
+ return -ENOMEM;
+
+ res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
+ if (unlikely(res < 0)) {
+ kvfree(p);
+ return res;
+ }
+ *pages = p;
+ return (res == n ? len : res * PAGE_SIZE) - *start;
+}
+
+static int iov_iter_npages_iovec(const struct iov_iter *i, int maxpages)
+{
+ size_t offset = i->iov_offset;
+ size_t size = i->count;
+ const struct iovec *iov = i->iov;
+ int npages = 0;
+ int n;
+
+ for (n = 0; size && n < i->nr_segs; n++, iov++) {
+ unsigned long addr = (unsigned long)iov->iov_base + offset;
+ size_t len = iov->iov_len - offset;
+ offset = 0;
+ if (unlikely(!len)) /* empty segment */
+ continue;
+ if (len > size)
+ len = size;
+ npages += (addr + len + PAGE_SIZE - 1) / PAGE_SIZE
+ - addr / PAGE_SIZE;
+ if (npages >= maxpages) /* don't bother going further */
+ return maxpages;
+ size -= len;
+ offset = 0;
+ }
+ return min(npages, maxpages);
+}
+
+static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
+{
+ char *from = kmap_atomic(page);
+ memcpy(to, from + offset, len);
+ kunmap_atomic(from);
+}
+
+static void memcpy_to_page(struct page *page, size_t offset, char *from, size_t len)
+{
+ char *to = kmap_atomic(page);
+ memcpy(to + offset, from, len);
+ kunmap_atomic(to);
+}
+
+static size_t copy_page_to_iter_bvec(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t skip, copy, wanted;
+ const struct bio_vec *bvec;
+ void *kaddr, *from;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ wanted = bytes;
+ bvec = i->bvec;
+ skip = i->iov_offset;
+ copy = min_t(size_t, bytes, bvec->bv_len - skip);
+
+ kaddr = kmap_atomic(page);
+ from = kaddr + offset;
+ memcpy_to_page(bvec->bv_page, skip + bvec->bv_offset, from, copy);
+ skip += copy;
+ from += copy;
+ bytes -= copy;
+ while (bytes) {
+ bvec++;
+ copy = min(bytes, (size_t)bvec->bv_len);
+ memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, copy);
+ skip = copy;
+ from += copy;
+ bytes -= copy;
+ }
+ kunmap_atomic(kaddr);
+ if (skip == bvec->bv_len) {
+ bvec++;
+ skip = 0;
+ }
+ i->count -= wanted - bytes;
+ i->nr_segs -= bvec - i->bvec;
+ i->bvec = bvec;
+ i->iov_offset = skip;
+ return wanted - bytes;
+}
+
+static size_t copy_page_from_iter_bvec(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t skip, copy, wanted;
+ const struct bio_vec *bvec;
+ void *kaddr, *to;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ wanted = bytes;
+ bvec = i->bvec;
+ skip = i->iov_offset;
+
+ kaddr = kmap_atomic(page);
+
+ to = kaddr + offset;
+
+ copy = min(bytes, bvec->bv_len - skip);
+
+ memcpy_from_page(to, bvec->bv_page, bvec->bv_offset + skip, copy);
+
+ to += copy;
+ skip += copy;
+ bytes -= copy;
+
+ while (bytes) {
+ bvec++;
+ copy = min(bytes, (size_t)bvec->bv_len);
+ memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, copy);
+ skip = copy;
+ to += copy;
+ bytes -= copy;
+ }
+ kunmap_atomic(kaddr);
+ if (skip == bvec->bv_len) {
+ bvec++;
+ skip = 0;
+ }
+ i->count -= wanted;
+ i->nr_segs -= bvec - i->bvec;
+ i->bvec = bvec;
+ i->iov_offset = skip;
+ return wanted;
+}
+
+static size_t copy_from_user_bvec(struct page *page,
+ struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+ char *kaddr;
+ size_t left;
+ const struct bio_vec *bvec;
+ size_t base = i->iov_offset;
+
+ kaddr = kmap_atomic(page);
+ for (left = bytes, bvec = i->bvec; left; bvec++, base = 0) {
+ size_t copy = min(left, bvec->bv_len - base);
+ if (!bvec->bv_len)
+ continue;
+ memcpy_from_page(kaddr + offset, bvec->bv_page,
+ bvec->bv_offset + base, copy);
+ offset += copy;
+ left -= copy;
+ }
+ kunmap_atomic(kaddr);
+ return bytes;
+}
+
+static void advance_bvec(struct iov_iter *i, size_t bytes)
+{
+ BUG_ON(i->count < bytes);
+
+ if (likely(i->nr_segs == 1)) {
+ i->iov_offset += bytes;
+ i->count -= bytes;
+ } else {
+ const struct bio_vec *bvec = i->bvec;
+ size_t base = i->iov_offset;
+ unsigned long nr_segs = i->nr_segs;
+
+ /*
+ * The !iov->iov_len check ensures we skip over unlikely
+ * zero-length segments (without overruning the iovec).
+ */
+ while (bytes || unlikely(i->count && !bvec->bv_len)) {
+ int copy;
+
+ copy = min(bytes, bvec->bv_len - base);
+ BUG_ON(!i->count || i->count < copy);
+ i->count -= copy;
+ bytes -= copy;
+ base += copy;
+ if (bvec->bv_len == base) {
+ bvec++;
+ nr_segs--;
+ base = 0;
+ }
+ }
+ i->bvec = bvec;
+ i->iov_offset = base;
+ i->nr_segs = nr_segs;
+ }
+}
+
+static unsigned long alignment_bvec(const struct iov_iter *i)
+{
+ const struct bio_vec *bvec = i->bvec;
+ unsigned long res;
+ size_t size = i->count;
+ size_t n;
+
+ if (!size)
+ return 0;
+
+ res = bvec->bv_offset + i->iov_offset;
+ n = bvec->bv_len - i->iov_offset;
+ if (n >= size)
+ return res | size;
+ size -= n;
+ res |= n;
+ while (size > (++bvec)->bv_len) {
+ res |= bvec->bv_offset | bvec->bv_len;
+ size -= bvec->bv_len;
+ }
+ res |= bvec->bv_offset | size;
+ return res;
+}
+
+static ssize_t get_pages_bvec(struct iov_iter *i,
+ struct page **pages, size_t maxsize,
+ size_t *start)
+{
+ const struct bio_vec *bvec = i->bvec;
+ size_t len = bvec->bv_len - i->iov_offset;
+ if (len > i->count)
+ len = i->count;
+ if (len > maxsize)
+ len = maxsize;
+ *start = bvec->bv_offset + i->iov_offset;
+
+ get_page(*pages = bvec->bv_page);
+
+ return len;
+}
+
+static ssize_t get_pages_alloc_bvec(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ size_t *start)
+{
+ const struct bio_vec *bvec = i->bvec;
+ size_t len = bvec->bv_len - i->iov_offset;
+ if (len > i->count)
+ len = i->count;
+ if (len > maxsize)
+ len = maxsize;
+ *start = bvec->bv_offset + i->iov_offset;
+
+ *pages = kmalloc(sizeof(struct page *), GFP_KERNEL);
+ if (!*pages)
+ return -ENOMEM;
+
+ get_page(**pages = bvec->bv_page);
+
+ return len;
+}
+
+static int iov_iter_npages_bvec(const struct iov_iter *i, int maxpages)
+{
+ size_t offset = i->iov_offset;
+ size_t size = i->count;
+ const struct bio_vec *bvec = i->bvec;
+ int npages = 0;
+ int n;
+
+ for (n = 0; size && n < i->nr_segs; n++, bvec++) {
+ size_t len = bvec->bv_len - offset;
+ offset = 0;
+ if (unlikely(!len)) /* empty segment */
+ continue;
+ if (len > size)
+ len = size;
+ npages++;
+ if (npages >= maxpages) /* don't bother going further */
+ return maxpages;
+ size -= len;
+ offset = 0;
+ }
+ return min(npages, maxpages);
+}
+
+size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ if (i->type & ITER_BVEC)
+ return copy_page_to_iter_bvec(page, offset, bytes, i);
+ else
+ return copy_page_to_iter_iovec(page, offset, bytes, i);
+}
+EXPORT_SYMBOL(copy_page_to_iter);
+
+size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ if (i->type & ITER_BVEC)
+ return copy_page_from_iter_bvec(page, offset, bytes, i);
+ else
+ return copy_page_from_iter_iovec(page, offset, bytes, i);
+}
+EXPORT_SYMBOL(copy_page_from_iter);
+
+size_t iov_iter_copy_from_user_atomic(struct page *page,
+ struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+ if (i->type & ITER_BVEC)
+ return copy_from_user_bvec(page, i, offset, bytes);
+ else
+ return copy_from_user_atomic_iovec(page, i, offset, bytes);
+}
+EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
+
+void iov_iter_advance(struct iov_iter *i, size_t size)
+{
+ if (i->type & ITER_BVEC)
+ advance_bvec(i, size);
+ else
+ advance_iovec(i, size);
+}
+EXPORT_SYMBOL(iov_iter_advance);
+
+/*
+ * Return the count of just the current iov_iter segment.
+ */
+size_t iov_iter_single_seg_count(const struct iov_iter *i)
+{
+ if (i->nr_segs == 1)
+ return i->count;
+ else if (i->type & ITER_BVEC)
+ return min(i->count, i->iov->iov_len - i->iov_offset);
+ else
+ return min(i->count, i->bvec->bv_len - i->iov_offset);
+}
+EXPORT_SYMBOL(iov_iter_single_seg_count);
+
+unsigned long iov_iter_alignment(const struct iov_iter *i)
+{
+ if (i->type & ITER_BVEC)
+ return alignment_bvec(i);
+ else
+ return alignment_iovec(i);
+}
+EXPORT_SYMBOL(iov_iter_alignment);
+
+ssize_t iov_iter_get_pages(struct iov_iter *i,
+ struct page **pages, size_t maxsize,
+ size_t *start)
+{
+ if (i->type & ITER_BVEC)
+ return get_pages_bvec(i, pages, maxsize, start);
+ else
+ return get_pages_iovec(i, pages, maxsize, start);
+}
+EXPORT_SYMBOL(iov_iter_get_pages);
+
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ size_t *start)
+{
+ if (i->type & ITER_BVEC)
+ return get_pages_alloc_bvec(i, pages, maxsize, start);
+ else
+ return get_pages_alloc_iovec(i, pages, maxsize, start);
+}
+EXPORT_SYMBOL(iov_iter_get_pages_alloc);
+
+int iov_iter_npages(const struct iov_iter *i, int maxpages)
+{
+ if (i->type & ITER_BVEC)
+ return iov_iter_npages_bvec(i, maxpages);
+ else
+ return iov_iter_npages_iovec(i, maxpages);
+}
+EXPORT_SYMBOL(iov_iter_npages);
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-04 13:25:56 +0000