ipc: Define shmem utilities for Linux and Android

src/xrt/ipc/CMakeLists.txt

@@ -24,6 +24,8 @@ proto_gen(${CMAKE_CURRENT_BINARY_DIR}/ipc_server_generated.c)
 
 set(IPC_COMMON_SOURCES
 	${CMAKE_CURRENT_BINARY_DIR}/ipc_protocol_generated.h
+	ipc_shmem.c
+	ipc_shmem.h
 	ipc_utils.c
 	ipc_utils.h)
 ###

src/xrt/ipc/ipc_shmem.c

@@ -0,0 +1,116 @@
+// Copyright 2020, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  IPC shared memory helpers
+ * @author Ryan Pavlik <ryan.pavlik@collabora.com>
+ * @author Pete Black <pblack@collabora.com>
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @ingroup ipc_internal
+ */
+
+#include <xrt/xrt_config_os.h>
+
+#include "ipc_shmem.h"
+
+#if defined(XRT_OS_UNIX)
+#include <sys/mman.h>
+#include <unistd.h>
+#endif
+
+#if defined(XRT_OS_ANDROID)
+#include <android/sharedmem.h>
+#elif defined(XRT_OS_UNIX)
+// non-android unix
+#include <sys/stat.h>
+#include <fcntl.h>
+#endif
+
+#if defined(XRT_OS_ANDROID)
+
+#if __ANDROID_API__ < 26
+#error "Android API level 26 or higher needed for ASharedMemory_create"
+#endif
+xrt_result_t
+
+ipc_shmem_create(size_t size, xrt_shmem_handle_t *out_handle, void **out_map)
+{
+
+	int fd = ASharedMemory_create("monado", size);
+	if (fd < 0) {
+		return XRT_ERROR_IPC_FAILURE;
+	}
+	xrt_result_t result = ipc_shmem_map(fd, size, out_map);
+	if (result != XRT_SUCCESS) {
+		close(fd);
+		return result;
+	}
+	*out_handle = fd;
+	return XRT_SUCCESS;
+}
+
+#elif defined(XRT_OS_UNIX)
+
+#define MONADO_SHMEM_NAME "/monado_shm"
+// Impl for non-Android Unix.
+xrt_result_t
+ipc_shmem_create(size_t size, xrt_shmem_handle_t *out_handle, void **out_map)
+{
+	*out_handle = -1;
+	int fd =
+	    shm_open(MONADO_SHMEM_NAME, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
+	if (fd < 0) {
+		return XRT_ERROR_IPC_FAILURE;
+	}
+
+	if (ftruncate(fd, size) < 0) {
+		close(fd);
+		return XRT_ERROR_IPC_FAILURE;
+	}
+	xrt_result_t result = ipc_shmem_map(fd, size, out_map);
+	if (result != XRT_SUCCESS) {
+		close(fd);
+		return result;
+	}
+
+	// Don't need the name entry anymore, we can share the FD.
+	shm_unlink(MONADO_SHMEM_NAME);
+	*out_handle = fd;
+	return XRT_SUCCESS;
+}
+
+#else
+#error "OS not yet supported"
+#endif
+
+#if defined(XRT_OS_UNIX)
+void
+ipc_shmem_destroy(xrt_shmem_handle_t *handle_ptr)
+{
+	if (handle_ptr == NULL) {
+		return;
+	}
+	xrt_shmem_handle_t handle = *handle_ptr;
+	if (handle < 0) {
+		return;
+	}
+	close(handle);
+	*handle_ptr = -1;
+}
+
+xrt_result_t
+ipc_shmem_map(xrt_shmem_handle_t handle, size_t size, void **out_map)
+{
+
+	const int access = PROT_READ | PROT_WRITE;
+	const int flags = MAP_SHARED;
+	void *ptr = mmap(NULL, size, access, flags, handle, 0);
+	if (ptr == NULL) {
+		return XRT_ERROR_IPC_FAILURE;
+	}
+	*out_map = ptr;
+	return XRT_SUCCESS;
+}
+#else
+#error "OS not yet supported"
+#endif

src/xrt/ipc/ipc_shmem.h

@@ -0,0 +1,70 @@
+// Copyright 2020, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief  Shared memory helpers
+ * @author Ryan Pavlik <ryan.pavlik@collabora.com>
+ * @ingroup ipc_internal
+ */
+
+#pragma once
+
+#include <xrt/xrt_handles.h>
+#include <xrt/xrt_results.h>
+
+#include <stddef.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*!
+ * @class xrt_shmem_handle_t
+ * @brief Generic typedef for platform-specific shared memory handle.
+ */
+/*!
+ * Create and map a shared memory region.
+ *
+ * @param[in] size Desired size of region
+ * @param[in,out] out_handle Pointer to the handle to populate. Receives the
+ * handle if this succeeds, or the invalid value if it fails.
+ * @param[in,out] out_map Pointer to the pointer to populate with the mapping of
+ * this shared memory region. On failure, contents are undefined.
+ *
+ * @public @memberof xrt_shmem_handle_t
+ */
+xrt_result_t
+ipc_shmem_create(size_t size, xrt_shmem_handle_t *out_handle, void **out_map);
+
+/*!
+ * Map a shared memory region.
+ *
+ * @param[in] handle Handle for region
+ * @param[in] size Size of region
+ * @param[in,out] out_map Pointer to the pointer to populate with the mapping of
+ * this shared memory region.
+ *
+ * @public @memberof xrt_shmem_handle_t
+ */
+xrt_result_t
+ipc_shmem_map(xrt_shmem_handle_t handle, size_t size, void **out_map);
+
+/*!
+ * Destroy a handle to a shared memory region.
+ *
+ * This probably does not destroy the underlying region, if other references to
+ * it (in this process or others) are still open.
+ *
+ * @param[in,out] handle_ptr Pointer to the handle to destroy - will be checked
+ * for validity, destroyed, and cleared.
+ *
+ * @public @memberof xrt_shmem_handle_t
+ */
+void
+ipc_shmem_destroy(xrt_shmem_handle_t *handle_ptr);
+
+#ifdef __cplusplus
+}
+#endif

src/xrt/ipc/meson.build

@@ -9,6 +9,8 @@ ipc_include = include_directories('.')
 prog_python = import('python').find_installation('python3')
 
 common_sources = [
+	'ipc_shmem.c',
+	'ipc_shmem.h',
 	'ipc_utils.c',
 	'ipc_utils.h',
 ]
@@ -44,7 +46,7 @@ lib_ipc_client = static_library(
 	include_directories: [
 		xrt_include,
 	],
-	dependencies: [aux]
+	dependencies: [aux, rt]
 )