[PATCH v3 2/7] binder: add functions to copy to/from binder buffers

From: Todd Kjos
Date: Fri Feb 08 2019 - 13:35:44 EST

Avoid vm_area when copying to or from binder buffers.
Instead, new copy functions are added that copy from
kernel space to binder buffer space. These use
kmap_atomic() and kunmap_atomic() to create temporary
mappings and then memcpy() is used to copy within
that page.

Also, kmap_atomic() / kunmap_atomic() use the appropriate
cache flushing to support VIVT cache architectures.
Allow binder to build if CPU_CACHE_VIVT is defined.

Several uses of the new functions are added here. More
to follow in subsequent patches.

Signed-off-by: Todd Kjos <tkjos@xxxxxxxxxx>
---
v2: remove casts as suggested by Dan Carpenter

drivers/android/Kconfig | 2 +-
drivers/android/binder.c | 119 +++++++++++++++++++++------------
drivers/android/binder_alloc.c | 59 ++++++++++++++++
drivers/android/binder_alloc.h | 12 ++++
4 files changed, 147 insertions(+), 45 deletions(-)

diff --git a/drivers/android/Kconfig b/drivers/android/Kconfig
index 4c190f8d1f4c6..6fdf2abe4598a 100644
--- a/drivers/android/Kconfig
+++ b/drivers/android/Kconfig
@@ -10,7 +10,7 @@ if ANDROID

config ANDROID_BINDER_IPC
bool "Android Binder IPC Driver"
- depends on MMU && !CPU_CACHE_VIVT
+ depends on MMU
default n
---help---
Binder is used in Android for both communication between processes,
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index ab0b3eec363bc..74d0c1ff874e2 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2244,14 +2244,22 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
off_end = (void *)off_start + buffer->offsets_size;
for (offp = off_start; offp < off_end; offp++) {
struct binder_object_header *hdr;
- size_t object_size = binder_validate_object(buffer, *offp);
-
+ size_t object_size;
+ binder_size_t object_offset;
+ binder_size_t buffer_offset = (uintptr_t)offp -
+ (uintptr_t)buffer->data;
+
+ binder_alloc_copy_from_buffer(&proc->alloc, &object_offset,
+ buffer, buffer_offset,
+ sizeof(object_offset));
+ object_size = binder_validate_object(buffer, object_offset);
if (object_size == 0) {
pr_err("transaction release %d bad object at offset %lld, size %zd\n",
- debug_id, (u64)*offp, buffer->data_size);
+ debug_id, (u64)object_offset, buffer->data_size);
continue;
}
- hdr = (struct binder_object_header *)(buffer->data + *offp);
+ hdr = (struct binder_object_header *)
+ (buffer->data + object_offset);
switch (hdr->type) {
case BINDER_TYPE_BINDER:
case BINDER_TYPE_WEAK_BINDER: {
@@ -2359,8 +2367,20 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
continue;
}
fd_array = (u32 *)(parent_buffer + (uintptr_t)fda->parent_offset);
- for (fd_index = 0; fd_index < fda->num_fds; fd_index++)
- binder_deferred_fd_close(fd_array[fd_index]);
+ for (fd_index = 0; fd_index < fda->num_fds;
+ fd_index++) {
+ u32 fd;
+ binder_size_t offset =
+ (uintptr_t)&fd_array[fd_index] -
+ (uintptr_t)buffer->data;
+
+ binder_alloc_copy_from_buffer(&proc->alloc,
+ &fd,
+ buffer,
+ offset,
+ sizeof(fd));
+ binder_deferred_fd_close(fd);
+ }
} break;
default:
pr_err("transaction release %d bad object type %x\n",
@@ -2496,7 +2516,7 @@ static int binder_translate_handle(struct flat_binder_object *fp,
return ret;
}

-static int binder_translate_fd(u32 *fdp,
+static int binder_translate_fd(u32 fd, binder_size_t fd_offset,
struct binder_transaction *t,
struct binder_thread *thread,
struct binder_transaction *in_reply_to)
@@ -2507,7 +2527,6 @@ static int binder_translate_fd(u32 *fdp,
struct file *file;
int ret = 0;
bool target_allows_fd;
- int fd = *fdp;

if (in_reply_to)
target_allows_fd = !!(in_reply_to->flags & TF_ACCEPT_FDS);
@@ -2546,7 +2565,7 @@ static int binder_translate_fd(u32 *fdp,
goto err_alloc;
}
fixup->file = file;
- fixup->offset = (uintptr_t)fdp - (uintptr_t)t->buffer->data;
+ fixup->offset = fd_offset;
trace_binder_transaction_fd_send(t, fd, fixup->offset);
list_add_tail(&fixup->fixup_entry, &t->fd_fixups);

@@ -2598,8 +2617,17 @@ static int binder_translate_fd_array(struct binder_fd_array_object *fda,
return -EINVAL;
}
for (fdi = 0; fdi < fda->num_fds; fdi++) {
- int ret = binder_translate_fd(&fd_array[fdi], t, thread,
- in_reply_to);
+ u32 fd;
+ int ret;
+ binder_size_t offset =
+ (uintptr_t)&fd_array[fdi] -
+ (uintptr_t)t->buffer->data;
+
+ binder_alloc_copy_from_buffer(&target_proc->alloc,
+ &fd, t->buffer,
+ offset, sizeof(fd));
+ ret = binder_translate_fd(fd, offset, t, thread,
+ in_reply_to);
if (ret < 0)
return ret;
}
@@ -3066,7 +3094,9 @@ static void binder_transaction(struct binder_proc *proc,

t->security_ctx = (uintptr_t)kptr +
binder_alloc_get_user_buffer_offset(&target_proc->alloc);
- memcpy(kptr, secctx, secctx_sz);
+ binder_alloc_copy_to_buffer(&target_proc->alloc,
+ t->buffer, buf_offset,
+ secctx, secctx_sz);
security_release_secctx(secctx, secctx_sz);
secctx = NULL;
}
@@ -3128,11 +3158,21 @@ static void binder_transaction(struct binder_proc *proc,
off_min = 0;
for (; offp < off_end; offp++) {
struct binder_object_header *hdr;
- size_t object_size = binder_validate_object(t->buffer, *offp);
-
- if (object_size == 0 || *offp < off_min) {
+ size_t object_size;
+ binder_size_t object_offset;
+ binder_size_t buffer_offset =
+ (uintptr_t)offp - (uintptr_t)t->buffer->data;
+
+ binder_alloc_copy_from_buffer(&target_proc->alloc,
+ &object_offset,
+ t->buffer,
+ buffer_offset,
+ sizeof(object_offset));
+ object_size = binder_validate_object(t->buffer, object_offset);
+ if (object_size == 0 || object_offset < off_min) {
binder_user_error("%d:%d got transaction with invalid offset (%lld, min %lld max %lld) or object.\n",
- proc->pid, thread->pid, (u64)*offp,
+ proc->pid, thread->pid,
+ (u64)object_offset,
(u64)off_min,
(u64)t->buffer->data_size);
return_error = BR_FAILED_REPLY;
@@ -3141,8 +3181,9 @@ static void binder_transaction(struct binder_proc *proc,
goto err_bad_offset;
}

- hdr = (struct binder_object_header *)(t->buffer->data + *offp);
- off_min = *offp + object_size;
+ hdr = (struct binder_object_header *)
+ (t->buffer->data + object_offset);
+ off_min = object_offset + object_size;
switch (hdr->type) {
case BINDER_TYPE_BINDER:
case BINDER_TYPE_WEAK_BINDER: {
@@ -3173,8 +3214,10 @@ static void binder_transaction(struct binder_proc *proc,

case BINDER_TYPE_FD: {
struct binder_fd_object *fp = to_binder_fd_object(hdr);
- int ret = binder_translate_fd(&fp->fd, t, thread,
- in_reply_to);
+ binder_size_t fd_offset = object_offset +
+ (uintptr_t)&fp->fd - (uintptr_t)fp;
+ int ret = binder_translate_fd(fp->fd, fd_offset, t,
+ thread, in_reply_to);

if (ret < 0) {
return_error = BR_FAILED_REPLY;
@@ -3967,6 +4010,7 @@ static int binder_wait_for_work(struct binder_thread *thread,

/**
* binder_apply_fd_fixups() - finish fd translation
+ * @proc: binder_proc associated @t->buffer
* @t: binder transaction with list of fd fixups
*
* Now that we are in the context of the transaction target
@@ -3978,14 +4022,14 @@ static int binder_wait_for_work(struct binder_thread *thread,
* fput'ing files that have not been processed and ksys_close'ing
* any fds that have already been allocated.
*/
-static int binder_apply_fd_fixups(struct binder_transaction *t)
+static int binder_apply_fd_fixups(struct binder_proc *proc,
+ struct binder_transaction *t)
{
struct binder_txn_fd_fixup *fixup, *tmp;
int ret = 0;

list_for_each_entry(fixup, &t->fd_fixups, fixup_entry) {
int fd = get_unused_fd_flags(O_CLOEXEC);
- u32 *fdp;

if (fd < 0) {
binder_debug(BINDER_DEBUG_TRANSACTION,
@@ -4000,33 +4044,20 @@ static int binder_apply_fd_fixups(struct binder_transaction *t)
trace_binder_transaction_fd_recv(t, fd, fixup->offset);
fd_install(fd, fixup->file);
fixup->file = NULL;
- fdp = (u32 *)(t->buffer->data + fixup->offset);
- /*
- * This store can cause problems for CPUs with a
- * VIVT cache (eg ARMv5) since the cache cannot
- * detect virtual aliases to the same physical cacheline.
- * To support VIVT, this address and the user-space VA
- * would both need to be flushed. Since this kernel
- * VA is not constructed via page_to_virt(), we can't
- * use flush_dcache_page() on it, so we'd have to use
- * an internal function. If devices with VIVT ever
- * need to run Android, we'll either need to go back
- * to patching the translated fd from the sender side
- * (using the non-standard kernel functions), or rework
- * how the kernel uses the buffer to use page_to_virt()
- * addresses instead of allocating in our own vm area.
- *
- * For now, we disable compilation if CONFIG_CPU_CACHE_VIVT.
- */
- *fdp = fd;
+ binder_alloc_copy_to_buffer(&proc->alloc, t->buffer,
+ fixup->offset, &fd,
+ sizeof(u32));
}
list_for_each_entry_safe(fixup, tmp, &t->fd_fixups, fixup_entry) {
if (fixup->file) {
fput(fixup->file);
} else if (ret) {
- u32 *fdp = (u32 *)(t->buffer->data + fixup->offset);
+ u32 fd;

- binder_deferred_fd_close(*fdp);
+ binder_alloc_copy_from_buffer(&proc->alloc, &fd,
+ t->buffer, fixup->offset,
+ sizeof(fd));
+ binder_deferred_fd_close(fd);
}
list_del(&fixup->fixup_entry);
kfree(fixup);
@@ -4324,7 +4355,7 @@ static int binder_thread_read(struct binder_proc *proc,
trd->sender_pid = 0;
}

- ret = binder_apply_fd_fixups(t);
+ ret = binder_apply_fd_fixups(proc, t);
if (ret) {
struct binder_buffer *buffer = t->buffer;
bool oneway = !!(t->flags & TF_ONE_WAY);
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 94c0d85c4e75b..2eebff4be83e0 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1166,3 +1166,62 @@ binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
}
return 0;
}
+
+static void binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
+ bool to_buffer,
+ struct binder_buffer *buffer,
+ binder_size_t buffer_offset,
+ void *ptr,
+ size_t bytes)
+{
+ /* All copies must be 32-bit aligned and 32-bit size */
+ BUG_ON(!check_buffer(alloc, buffer, buffer_offset, bytes));
+
+ while (bytes) {
+ unsigned long size;
+ struct page *page;
+ pgoff_t pgoff;
+ void *tmpptr;
+ void *base_ptr;
+
+ page = binder_alloc_get_page(alloc, buffer,
+ buffer_offset, &pgoff);
+ size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
+ base_ptr = kmap_atomic(page);
+ tmpptr = base_ptr + pgoff;
+ if (to_buffer)
+ memcpy(tmpptr, ptr, size);
+ else
+ memcpy(ptr, tmpptr, size);
+ /*
+ * kunmap_atomic() takes care of flushing the cache
+ * if this device has VIVT cache arch
+ */
+ kunmap_atomic(base_ptr);
+ bytes -= size;
+ pgoff = 0;
+ ptr = ptr + size;
+ buffer_offset += size;
+ }
+}
+
+void binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
+ struct binder_buffer *buffer,
+ binder_size_t buffer_offset,
+ void *src,
+ size_t bytes)
+{
+ binder_alloc_do_buffer_copy(alloc, true, buffer, buffer_offset,
+ src, bytes);
+}
+
+void binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
+ void *dest,
+ struct binder_buffer *buffer,
+ binder_size_t buffer_offset,
+ size_t bytes)
+{
+ binder_alloc_do_buffer_copy(alloc, false, buffer, buffer_offset,
+ dest, bytes);
+}
+
diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index 995155f31dbd4..9d682b9d6c241 100644
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -191,5 +191,17 @@ binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
const void __user *from,
size_t bytes);

+void binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
+ struct binder_buffer *buffer,
+ binder_size_t buffer_offset,
+ void *src,
+ size_t bytes);
+
+void binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
+ void *dest,
+ struct binder_buffer *buffer,
+ binder_size_t buffer_offset,
+ size_t bytes);
+
#endif /* _LINUX_BINDER_ALLOC_H */

--
2.20.1.791.gb4d0f1c61a-goog