monado/src/xrt/ipc/ipc_shmem.c

// 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