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Add processing of code coverage for optee core #4192

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Add processing of code coverage for optee core #4192

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Commits on Nov 2, 2020

  1. core: add configuration flags for gcov 

    This patch adds the flags to configure the use of gcov:
 - CFG_CORE_GCOV_SUPPORT: enable the coverage for the core
 - CFG_TA_GCOV_SUPPORT: enable the coverage for TAs

If any of them is enabled, CFG_GCOV_SUPPORT is enabled

These flags are exported to the devkit.

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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    lenormandfranck committed Nov 2, 2020
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  2. compil: Fix link error TEE_RAM_VA_SIZE is too small 

    For imx 6 qnd 7 targets, the build fails because TEE_RAM_VA_SIZE
is too small. This patch increase it from 512ko to 2 Mo when coverage
is enabled.

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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    lenormandfranck committed Nov 2, 2020
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  3. libgcov: Add library adding the gcov support 

    The code coverage is a metric measuring the lines of code
executed in a code base during execution.
If the code coverage is generated after a test suite is
ran, it will give the coverage of code tested by the
test suite. It gives the possibility to identify the code
which is not tested.

The gcov code coverage is supported by different compiler:
 - GCC (gcc.gnu.org/onlinedocs/gcc/Gcov.html)
 - clang compiler (clang.llvm.org/docs/SourceBasedCodeCoverage.html)
It allows to analyze which part of the code is executed.
The interface with a specific implementation of gcov is defined
usign the structure gcov_impl_t.

The library implements the symbol required for gcov:
 - __gcov_init: called by each coverage unit
 - __gcov_merge_add
 - __gcov_exit
The calls to these symbols are redirected to the implementation
for the compiler used.

The library role is to transform the coverage data in program
memory to a valid gcov data file. For this it interacts with:
 - user/TA: Control (Reset or Dump) the coverage data
 - Function to store data: Send the data to it for storage in REE FS

In order to retrieve the coverage (*.gcda) for a specific UC,
it is recommended to do the following actions:
 - clear the coverage
 - perform the UC
 - save the coverage

Note: The core and the TAs are linked against different instances
of the libgcov. The libgcov of the core can be controlled by the
gcov PTA. The TA instances are controlled calling the libgcov API.

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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    lenormandfranck committed Nov 2, 2020
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  4. libgcov: Add implementation of gcov for GCC 

    The compiler GCC implements gcov code coverage and this patch
adds the support to handle the structure in memory generated
by the compiler. It also handles the transformation of the
structure in memory into gcov data files.

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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    lenormandfranck committed Nov 2, 2020
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  5. core: Add writer of coverage data to REE FS 

    The coverage data are generated during execution, in order to
exploit it, the data can be stored to REE FS in clear text
which is done by the writer.

The writer receives the data to store and call the dedicated
RPC to instruct the TEE client to store it in REE FS.

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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  6. pta: gcov: Add gcov pta 

    The PTA has two main purposes:
 - Control the code coverage of the core:
   - PTA_CMD_GCOV_GET_VERSION
   - PTA_CMD_GCOV_CORE_RESET
   - PTA_CMD_GCOV_CORE_DUMP_ALL
 - Write code coverage data from a TA (called by libgcov)
   - PTA_CMD_GCOV_DUMP

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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    lenormandfranck committed Nov 2, 2020
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  7. core: Add support for code coverage compilation 

    The code coverage is performed at runtime by keeping in memory
structures holding the releveant data:

In order to generate the code coverage, two steps are required:
 - Instruct the compiler to generate coverage information structure
   and functions to initialize them: flag --coverage.
 - Call the constructors added to initialize the coverage information
   and register them to the libgcov (modification of boot.c)

When an object file (.o) is created with code coverage support, a note
(.gcno) file is created with it. The note file contains informations
used when creating the code coverage report.

The support of code coverage in compiled code increases its size (~15%)
and the compilation time (~25%).

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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    lenormandfranck committed Nov 2, 2020
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  8. coverage.py: Add script to process code coverage 

    This script ease the generation of code coverage report. A report
is based on a codebase, note files (generated at compilation) and
data files (generated at runtime).
The report is generated using lcov and present the code coverage as
a percentage of lines executed compared to the total number of lines
in the codebase.

The script will copy all the note and data files in a temporary
directory allowing to reuse the generated artifact and checks that
the note and data file are correctly organised (the files must be
in the same directory).

The script also allow to generate an html output using genhtml and
to view it.

Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
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    lenormandfranck committed Nov 2, 2020
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