docs: sphinixfy gcov.txt and move to dev-tools

No textual changes beyond formatting.

Cc: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/gcov.txt → Documentation/dev-tools/gcov.rst

 Using gcov with the Linux kernel
 ================================
 
-1. Introduction
-2. Preparation
-3. Customization
-4. Files
-5. Modules
-6. Separated build and test machines
-7. Troubleshooting
-Appendix A: sample script: gather_on_build.sh
-Appendix B: sample script: gather_on_test.sh
-
-
-1. Introduction
-===============
-
 gcov profiling kernel support enables the use of GCC's coverage testing
-tool gcov [1] with the Linux kernel. Coverage data of a running kernel
+tool gcov_ with the Linux kernel. Coverage data of a running kernel
 is exported in gcov-compatible format via the "gcov" debugfs directory.
 To get coverage data for a specific file, change to the kernel build
-directory and use gcov with the -o option as follows (requires root):
+directory and use gcov with the ``-o`` option as follows (requires root)::
 
-# cd /tmp/linux-out
-# gcov -o /sys/kernel/debug/gcov/tmp/linux-out/kernel spinlock.c
+    # cd /tmp/linux-out
+    # gcov -o /sys/kernel/debug/gcov/tmp/linux-out/kernel spinlock.c
 
 This will create source code files annotated with execution counts
 in the current directory. In addition, graphical gcov front-ends such
-as lcov [2] can be used to automate the process of collecting data
+as lcov_ can be used to automate the process of collecting data
 for the entire kernel and provide coverage overviews in HTML format.
 
 Possible uses:
@@ -36,25 +22,23 @@ Possible uses:
 * minimizing kernel configurations (do I need this option if the
   associated code is never run?)
 
---
-
-[1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
-[2] http://ltp.sourceforge.net/coverage/lcov.php
+.. _gcov: http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
+.. _lcov: http://ltp.sourceforge.net/coverage/lcov.php
 
 
-2. Preparation
-==============
+Preparation
+-----------
 
-Configure the kernel with:
+Configure the kernel with::
 
         CONFIG_DEBUG_FS=y
         CONFIG_GCOV_KERNEL=y
 
-select the gcc's gcov format, default is autodetect based on gcc version:
+select the gcc's gcov format, default is autodetect based on gcc version::
 
         CONFIG_GCOV_FORMAT_AUTODETECT=y
 
-and to get coverage data for the entire kernel:
+and to get coverage data for the entire kernel::
 
         CONFIG_GCOV_PROFILE_ALL=y
 
@@ -63,58 +47,62 @@ larger and run slower. Also CONFIG_GCOV_PROFILE_ALL may not be supported
 on all architectures.
 
 Profiling data will only become accessible once debugfs has been
-mounted:
+mounted::
 
         mount -t debugfs none /sys/kernel/debug
 
 
-3. Customization
-================
+Customization
+-------------
 
 To enable profiling for specific files or directories, add a line
 similar to the following to the respective kernel Makefile:
 
-        For a single file (e.g. main.o):
+- For a single file (e.g. main.o)::
+
 	GCOV_PROFILE_main.o := y
 
-        For all files in one directory:
+- For all files in one directory::
+
 	GCOV_PROFILE := y
 
 To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
-is specified, use:
+is specified, use::
 
 	GCOV_PROFILE_main.o := n
-        and:
+
+and::
+
 	GCOV_PROFILE := n
 
 Only files which are linked to the main kernel image or are compiled as
 kernel modules are supported by this mechanism.
 
 
-4. Files
-========
+Files
+-----
 
 The gcov kernel support creates the following files in debugfs:
 
-        /sys/kernel/debug/gcov
+``/sys/kernel/debug/gcov``
 	Parent directory for all gcov-related files.
 
-        /sys/kernel/debug/gcov/reset
+``/sys/kernel/debug/gcov/reset``
 	Global reset file: resets all coverage data to zero when
         written to.
 
-        /sys/kernel/debug/gcov/path/to/compile/dir/file.gcda
+``/sys/kernel/debug/gcov/path/to/compile/dir/file.gcda``
 	The actual gcov data file as understood by the gcov
         tool. Resets file coverage data to zero when written to.
 
-        /sys/kernel/debug/gcov/path/to/compile/dir/file.gcno
+``/sys/kernel/debug/gcov/path/to/compile/dir/file.gcno``
 	Symbolic link to a static data file required by the gcov
         tool. This file is generated by gcc when compiling with
-                option -ftest-coverage.
+        option ``-ftest-coverage``.
 
 
-5. Modules
-==========
+Modules
+-------
 
 Kernel modules may contain cleanup code which is only run during
 module unload time. The gcov mechanism provides a means to collect
@@ -124,7 +112,7 @@ Once the module is loaded again, the associated coverage counters are
 initialized with the data from its previous instantiation.
 
 This behavior can be deactivated by specifying the gcov_persist kernel
-parameter:
+parameter::
 
         gcov_persist=0
 
@@ -132,8 +120,8 @@ At run-time, a user can also choose to discard data for an unloaded
 module by writing to its data file or the global reset file.
 
 
-6. Separated build and test machines
-====================================
+Separated build and test machines
+---------------------------------
 
 The gcov kernel profiling infrastructure is designed to work out-of-the
 box for setups where kernels are built and run on the same machine. In
@@ -142,36 +130,36 @@ must be made, depending on where the gcov tool is used:
 
 a) gcov is run on the TEST machine
 
-The gcov tool version on the test machine must be compatible with the
-gcc version used for kernel build. Also the following files need to be
-copied from build to test machine:
+    The gcov tool version on the test machine must be compatible with the
+    gcc version used for kernel build. Also the following files need to be
+    copied from build to test machine:
 
-from the source tree:
+    from the source tree:
       - all C source files + headers
 
-from the build tree:
+    from the build tree:
       - all C source files + headers
       - all .gcda and .gcno files
       - all links to directories
 
-It is important to note that these files need to be placed into the
-exact same file system location on the test machine as on the build
-machine. If any of the path components is symbolic link, the actual
-directory needs to be used instead (due to make's CURDIR handling).
+    It is important to note that these files need to be placed into the
+    exact same file system location on the test machine as on the build
+    machine. If any of the path components is symbolic link, the actual
+    directory needs to be used instead (due to make's CURDIR handling).
 
 b) gcov is run on the BUILD machine
 
-The following files need to be copied after each test case from test
-to build machine:
+    The following files need to be copied after each test case from test
+    to build machine:
 
-from the gcov directory in sysfs:
+    from the gcov directory in sysfs:
       - all .gcda files
       - all links to .gcno files
 
-These files can be copied to any location on the build machine. gcov
-must then be called with the -o option pointing to that directory.
+    These files can be copied to any location on the build machine. gcov
+    must then be called with the -o option pointing to that directory.
 
-Example directory setup on the build machine:
+    Example directory setup on the build machine::
 
       /tmp/linux:    kernel source tree
       /tmp/out:      kernel build directory as specified by make O=
@@ -181,77 +169,88 @@ Example directory setup on the build machine:
       [user@build] gcov -o /tmp/coverage/tmp/out/init main.c
 
 
-7. Troubleshooting
-==================
+Troubleshooting
+---------------
+
+Problem
+    Compilation aborts during linker step.
 
-Problem:  Compilation aborts during linker step.
-Cause:    Profiling flags are specified for source files which are not
+Cause
+    Profiling flags are specified for source files which are not
     linked to the main kernel or which are linked by a custom
     linker procedure.
-Solution: Exclude affected source files from profiling by specifying
-          GCOV_PROFILE := n or GCOV_PROFILE_basename.o := n in the
+
+Solution
+    Exclude affected source files from profiling by specifying
+    ``GCOV_PROFILE := n`` or ``GCOV_PROFILE_basename.o := n`` in the
     corresponding Makefile.
 
-Problem:  Files copied from sysfs appear empty or incomplete.
-Cause:    Due to the way seq_file works, some tools such as cp or tar
+Problem
+    Files copied from sysfs appear empty or incomplete.
+
+Cause
+    Due to the way seq_file works, some tools such as cp or tar
     may not correctly copy files from sysfs.
-Solution: Use 'cat' to read .gcda files and 'cp -d' to copy links.
+
+Solution
+    Use ``cat``' to read ``.gcda`` files and ``cp -d`` to copy links.
     Alternatively use the mechanism shown in Appendix B.
 
 
 Appendix A: gather_on_build.sh
-==============================
+------------------------------
 
 Sample script to gather coverage meta files on the build machine
-(see 6a):
-#!/bin/bash
+(see 6a)::
+
+    #!/bin/bash
 
-KSRC=$1
-KOBJ=$2
-DEST=$3
+    KSRC=$1
+    KOBJ=$2
+    DEST=$3
 
-if [ -z "$KSRC" ] || [ -z "$KOBJ" ] || [ -z "$DEST" ]; then
+    if [ -z "$KSRC" ] || [ -z "$KOBJ" ] || [ -z "$DEST" ]; then
       echo "Usage: $0 <ksrc directory> <kobj directory> <output.tar.gz>" >&2
       exit 1
-fi
+    fi
 
-KSRC=$(cd $KSRC; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
-KOBJ=$(cd $KOBJ; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
+    KSRC=$(cd $KSRC; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
+    KOBJ=$(cd $KOBJ; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
 
-find $KSRC $KOBJ \( -name '*.gcno' -o -name '*.[ch]' -o -type l \) -a \
+    find $KSRC $KOBJ \( -name '*.gcno' -o -name '*.[ch]' -o -type l \) -a \
                      -perm /u+r,g+r | tar cfz $DEST -P -T -
 
-if [ $? -eq 0 ] ; then
+    if [ $? -eq 0 ] ; then
       echo "$DEST successfully created, copy to test system and unpack with:"
       echo "  tar xfz $DEST -P"
-else
+    else
       echo "Could not create file $DEST"
-fi
+    fi
 
 
 Appendix B: gather_on_test.sh
-=============================
+-----------------------------
 
 Sample script to gather coverage data files on the test machine
-(see 6b):
+(see 6b)::
 
-#!/bin/bash -e
+    #!/bin/bash -e
 
-DEST=$1
-GCDA=/sys/kernel/debug/gcov
+    DEST=$1
+    GCDA=/sys/kernel/debug/gcov
 
-if [ -z "$DEST" ] ; then
+    if [ -z "$DEST" ] ; then
       echo "Usage: $0 <output.tar.gz>" >&2
       exit 1
-fi
-
-TEMPDIR=$(mktemp -d)
-echo Collecting data..
-find $GCDA -type d -exec mkdir -p $TEMPDIR/\{\} \;
-find $GCDA -name '*.gcda' -exec sh -c 'cat < $0 > '$TEMPDIR'/$0' {} \;
-find $GCDA -name '*.gcno' -exec sh -c 'cp -d $0 '$TEMPDIR'/$0' {} \;
-tar czf $DEST -C $TEMPDIR sys
-rm -rf $TEMPDIR
-
-echo "$DEST successfully created, copy to build system and unpack with:"
-echo "  tar xfz $DEST"
+    fi
+
+    TEMPDIR=$(mktemp -d)
+    echo Collecting data..
+    find $GCDA -type d -exec mkdir -p $TEMPDIR/\{\} \;
+    find $GCDA -name '*.gcda' -exec sh -c 'cat < $0 > '$TEMPDIR'/$0' {} \;
+    find $GCDA -name '*.gcno' -exec sh -c 'cp -d $0 '$TEMPDIR'/$0' {} \;
+    tar czf $DEST -C $TEMPDIR sys
+    rm -rf $TEMPDIR
+
+    echo "$DEST successfully created, copy to build system and unpack with:"
+    echo "  tar xfz $DEST"

Documentation/dev-tools/tools.rst

@@ -17,3 +17,4 @@ whole; patches welcome!
    coccinelle
    sparse
    kcov
+   gcov

MAINTAINERS

@@ -5118,7 +5118,7 @@ GCOV BASED KERNEL PROFILING
 M:	Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
 S:	Maintained
 F:	kernel/gcov/
-F:	Documentation/gcov.txt
+F:	Documentation/dev-tools/gcov.rst
 
 GDT SCSI DISK ARRAY CONTROLLER DRIVER
 M:	Achim Leubner <achim_leubner@adaptec.com>