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android: binder: support for file-descriptor arrays.

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This patch introduces a new binder_fd_array object,
that allows us to support one or more file descriptors
embedded in a buffer that is scatter-gathered.

Change-Id: I647a53cf0d905c7be0dfd9333806982def68dd74
Signed-off-by: Martijn Coenen <maco@google.com>
This commit is contained in:
Martijn Coenen
2016-10-18 13:58:55 +02:00
committed by Martijn Coenen
parent dd9bc4f9f1
commit e124de3827
2 changed files with 165 additions and 0 deletions
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28
include/uapi/linux/android/binder.h
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@@ -33,6 +33,7 @@ enum {
BINDER_TYPE_HANDLE = B_PACK_CHARS('s', 'h', '*', B_TYPE_LARGE),
BINDER_TYPE_WEAK_HANDLE = B_PACK_CHARS('w', 'h', '*', B_TYPE_LARGE),
BINDER_TYPE_FD = B_PACK_CHARS('f', 'd', '*', B_TYPE_LARGE),
BINDER_TYPE_FDA = B_PACK_CHARS('f', 'd', 'a', B_TYPE_LARGE),
BINDER_TYPE_PTR = B_PACK_CHARS('p', 't', '*', B_TYPE_LARGE),
};
@@ -129,6 +130,33 @@ enum {
BINDER_BUFFER_FLAG_HAS_PARENT = 0x01,
};
/* struct binder_fd_array_object - object describing an array of fds in a buffer
* @hdr: common header structure
* @num_fds: number of file descriptors in the buffer
* @parent: index in offset array to buffer holding the fd array
* @parent_offset: start offset of fd array in the buffer
*
* A binder_fd_array object represents an array of file
* descriptors embedded in a binder_buffer_object. It is
* different from a regular binder_buffer_object because it
* describes a list of file descriptors to fix up, not an opaque
* blob of memory, and hence the kernel needs to treat it differently.
*
* An example of how this would be used is with Android's
* native_handle_t object, which is a struct with a list of integers
* and a list of file descriptors. The native_handle_t struct itself
* will be represented by a struct binder_buffer_objct, whereas the
* embedded list of file descriptors is represented by a
* struct binder_fd_array_object with that binder_buffer_object as
* a parent.
*/
struct binder_fd_array_object {
struct binder_object_header hdr;
binder_size_t num_fds;
binder_size_t parent;
binder_size_t parent_offset;
};
/*
* On 64-bit platforms where user code may run in 32-bits the driver must
* translate the buffer (and local binder) addresses appropriately.