[Fuchsia] Move allocation of PA_HND identifiers into LaunchOptions.
Mojo's PlatformChannel implemented its own mechanism to allocate PA_HND
identifiers, and used the PA_USER0 namespace. Separately we had some
callers expecting to use statically-defined PA_USER0 identifiers to pass
application-specific handles, creating potential for clashes.
For features like base::FieldTrialList we also need a mechanism to pass
a handle to a child process at startup, for which we'd ideally have a
well-known path location in the FDIO namespace supplied to the child.
Since FDIO namespaces do not yet support non-file/directory handles, we
need a safe way to allocate an id that the FieldTrial implementation can
pass via the command-line, similarly to Mojo.
We add an AddHandleToTransfer() helper that appends a handle to a
handles-to-transfer vector with a unique id, and returns the id, and add
comments to clarify that PA_USER1 is used for these ids, leaving
PA_USER0 (and others) free for application use.
Bug: 909851
Change-Id: If9b8ffaf98155f72cc7a52e5ef0c51ef19048d66
Reviewed-on: https://chromium-review.googlesource.com/c/1354398
Reviewed-by: Kevin Marshall <[email protected]>
Reviewed-by: Sergey Ulanov <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Commit-Queue: Wez <[email protected]>
Cr-Commit-Position: refs/heads/master@{#612899}diff --git a/base/process/launch.h b/base/process/launch.h
index 31c6ba6..61db1bcc 100644
--- a/base/process/launch.h
+++ b/base/process/launch.h
@@ -199,8 +199,17 @@
// PA_HND() macro. The child retrieves the handle
// |zx_take_startup_handle(id)|. The supplied handles are consumed by
// LaunchProcess() even on failure.
+ // Note that PA_USER1 ids are reserved for use by AddHandleToTransfer(), below
+ // and by convention PA_USER0 is reserved for use by the embedding
+ // application.
HandlesToTransferVector handles_to_transfer;
+ // Allocates a unique id for |handle| in |handles_to_transfer|, inserts it,
+ // and returns the generated id.
+ static uint32_t AddHandleToTransfer(
+ HandlesToTransferVector* handles_to_transfer,
+ zx_handle_t handle);
+
// Specifies which basic capabilities to grant to the child process.
// By default the child process will receive the caller's complete namespace,
// access to the current base::fuchsia::DefaultJob(), handles for stdio and
