ION BUFFER SHARING UTILITY
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==========================
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File: ion_test.sh : Utility to test ION driver buffer sharing mechanism.
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Author: Pintu Kumar <pintu.ping@gmail.com>
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Introduction:
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-------------
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This is a test utility to verify ION buffer sharing in user space
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between 2 independent processes.
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It uses unix domain socket (with SCM_RIGHTS) as IPC to transfer an FD to
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another process to share the same buffer.
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This utility demonstrates how ION buffer sharing can be implemented between
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two user space processes, using various heap types.
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The following heap types are supported by ION driver.
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ION_HEAP_TYPE_SYSTEM (0)
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ION_HEAP_TYPE_SYSTEM_CONTIG (1)
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ION_HEAP_TYPE_CARVEOUT (2)
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ION_HEAP_TYPE_CHUNK (3)
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ION_HEAP_TYPE_DMA (4)
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By default only the SYSTEM and SYSTEM_CONTIG heaps are supported.
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Each heap is associated with the respective heap id.
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This utility is designed in the form of client/server program.
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The server part (ionapp_export) is the exporter of the buffer.
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It is responsible for creating an ION client, allocating the buffer based on
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the heap id, writing some data to this buffer and then exporting the FD
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(associated with this buffer) to another process using socket IPC.
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This FD is called as buffer FD (which is different than the ION client FD).
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The client part (ionapp_import) is the importer of the buffer.
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It retrives the FD from the socket data and installs into its address space.
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This new FD internally points to the same kernel buffer.
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So first it reads the data that is stored in this buffer and prints it.
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Then it writes the different size of data (it could be different data) to the
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same buffer.
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Finally the buffer FD must be closed by both the exporter and importer.
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Thus the same kernel buffer is shared among two user space processes using
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ION driver and only one time allocation.
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Prerequisite:
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-------------
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This utility works only if /dev/ion interface is present.
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The following configs needs to be enabled in kernel to include ion driver.
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CONFIG_ANDROID=y
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CONFIG_STAGING=y
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CONFIG_ION=y
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CONFIG_ION_SYSTEM_HEAP=y
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This utility requires to be run as root user.
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Compile and test:
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-----------------
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This utility is made to be run as part of kselftest framework in kernel.
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To compile and run using kselftest you can simply do the following from the
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kernel top directory.
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linux$ make TARGETS=android kselftest
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Or you can also use:
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linux$ make -C tools/testing/selftests TARGETS=android run_tests
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Using the selftest it can directly execute the ion_test.sh script to test the
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buffer sharing using ion system heap.
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Currently the heap size is hard coded as just 10 bytes inside this script.
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You need to be a root user to run under selftest.
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You can also compile and test manually using the following steps:
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ion$ make
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These will generate 2 executable: ionapp_export, ionapp_import
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Now you can run the export and import manually by specifying the heap type
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and the heap size.
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You can also directly execute the shell script to run the test automatically.
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Simply use the following command to run the test.
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ion$ sudo ./ion_test.sh
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Test Results:
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-------------
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The utility is verified on Ubuntu-32 bit system with Linux Kernel 4.14.
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Here is the snapshot of the test result using kselftest.
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linux# make TARGETS=android kselftest
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heap_type: 0, heap_size: 10
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--------------------------------------
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heap type: 0
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heap id: 1
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heap name: ion_system_heap
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--------------------------------------
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Fill buffer content:
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0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd
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Sharing fd: 6, Client fd: 5
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<ion_close_buffer_fd>: buffer release successfully....
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Received buffer fd: 4
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Read buffer content:
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0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0x0 0x0 0x0 0x0 0x0 0x0
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0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0
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Fill buffer content:
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0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd
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0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd 0xfd
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0xfd 0xfd
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<ion_close_buffer_fd>: buffer release successfully....
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ion_test.sh: heap_type: 0 - [PASS]
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ion_test.sh: done
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