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>

3 files changed, 257 insertions, 257 deletions

diff --git a/Documentation/dev-tools/gcov.rst b/Documentation/dev-tools/gcov.rst
new file mode 100644
index 000000000000..19eedfea8800
--- /dev/null
+++ b/Documentation/dev-tools/gcov.rst
@@ -0,0 +1,256 @@
+Using gcov with the Linux kernel
+================================
+
+gcov profiling kernel support enables the use of GCC's coverage testing
+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)::
+
+    # 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_ can be used to automate the process of collecting data
+for the entire kernel and provide coverage overviews in HTML format.
+
+Possible uses:
+
+* debugging (has this line been reached at all?)
+* test improvement (how do I change my test to cover these lines?)
+* minimizing kernel configurations (do I need this option if the
+  associated code is never run?)
+
+.. _gcov: http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
+.. _lcov: http://ltp.sourceforge.net/coverage/lcov.php
+
+
+Preparation
+-----------
+
+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::
+
+        CONFIG_GCOV_FORMAT_AUTODETECT=y
+
+and to get coverage data for the entire kernel::
+
+        CONFIG_GCOV_PROFILE_ALL=y
+
+Note that kernels compiled with profiling flags will be significantly
+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::
+
+        mount -t debugfs none /sys/kernel/debug
+
+
+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)::
+
+	GCOV_PROFILE_main.o := y
+
+- For all files in one directory::
+
+	GCOV_PROFILE := y
+
+To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
+is specified, use::
+
+	GCOV_PROFILE_main.o := n
+
+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.
+
+
+Files
+-----
+
+The gcov kernel support creates the following files in debugfs:
+
+``/sys/kernel/debug/gcov``
+	Parent directory for all gcov-related files.
+
+``/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``
+	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``
+	Symbolic link to a static data file required by the gcov
+        tool. This file is generated by gcc when compiling with
+        option ``-ftest-coverage``.
+
+
+Modules
+-------
+
+Kernel modules may contain cleanup code which is only run during
+module unload time. The gcov mechanism provides a means to collect
+coverage data for such code by keeping a copy of the data associated
+with the unloaded module. This data remains available through debugfs.
+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::
+
+        gcov_persist=0
+
+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.
+
+
+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
+cases where the kernel runs on a separate machine, special preparations
+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:
+
+    from the source tree:
+      - all C source files + headers
+
+    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).
+
+b) gcov is run on the BUILD machine
+
+    The following files need to be copied after each test case from test
+    to build machine:
+
+    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.
+
+    Example directory setup on the build machine::
+
+      /tmp/linux:    kernel source tree
+      /tmp/out:      kernel build directory as specified by make O=
+      /tmp/coverage: location of the files copied from the test machine
+
+      [user@build] cd /tmp/out
+      [user@build] gcov -o /tmp/coverage/tmp/out/init main.c
+
+
+Troubleshooting
+---------------
+
+Problem
+    Compilation aborts during linker step.
+
+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
+    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
+    may not correctly copy files from sysfs.
+
+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
+
+    KSRC=$1
+    KOBJ=$2
+    DEST=$3
+
+    if [ -z "$KSRC" ] || [ -z "$KOBJ" ] || [ -z "$DEST" ]; then
+      echo "Usage: $0 <ksrc directory> <kobj directory> <output.tar.gz>" >&2
+      exit 1
+    fi
+
+    KSRC=$(cd $KSRC; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
+    KOBJ=$(cd $KOBJ; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
+
+    find $KSRC $KOBJ \( -name '*.gcno' -o -name '*.[ch]' -o -type l \) -a \
+                     -perm /u+r,g+r | tar cfz $DEST -P -T -
+
+    if [ $? -eq 0 ] ; then
+      echo "$DEST successfully created, copy to test system and unpack with:"
+      echo "  tar xfz $DEST -P"
+    else
+      echo "Could not create file $DEST"
+    fi
+
+
+Appendix B: gather_on_test.sh
+-----------------------------
+
+Sample script to gather coverage data files on the test machine
+(see 6b)::
+
+    #!/bin/bash -e
+
+    DEST=$1
+    GCDA=/sys/kernel/debug/gcov
+
+    if [ -z "$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"
diff --git a/Documentation/dev-tools/tools.rst b/Documentation/dev-tools/tools.rst
index 9dcd0236a1ff..404d044c8518 100644
--- a/Documentation/dev-tools/tools.rst
+++ b/Documentation/dev-tools/tools.rst
@@ -17,3 +17,4 @@ whole; patches welcome!
    coccinelle
    sparse
    kcov
+   gcov
diff --git a/Documentation/gcov.txt b/Documentation/gcov.txt
deleted file mode 100644
index 7b727783db7e..000000000000
--- a/Documentation/gcov.txt
+++ /dev/null
@@ -1,257 +0,0 @@
-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
-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):
-
-# 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
-for the entire kernel and provide coverage overviews in HTML format.
-
-Possible uses:
-
-* debugging (has this line been reached at all?)
-* test improvement (how do I change my test to cover these lines?)
-* 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
-
-
-2. Preparation
-==============
-
-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:
-
-        CONFIG_GCOV_FORMAT_AUTODETECT=y
-
-and to get coverage data for the entire kernel:
-
-        CONFIG_GCOV_PROFILE_ALL=y
-
-Note that kernels compiled with profiling flags will be significantly
-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:
-
-        mount -t debugfs none /sys/kernel/debug
-
-
-3. 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):
-                GCOV_PROFILE_main.o := y
-
-        For all files in one directory:
-                GCOV_PROFILE := y
-
-To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
-is specified, use:
-
-                GCOV_PROFILE_main.o := n
-        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
-========
-
-The gcov kernel support creates the following files in debugfs:
-
-        /sys/kernel/debug/gcov
-                Parent directory for all gcov-related files.
-
-        /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
-                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
-                Symbolic link to a static data file required by the gcov
-                tool. This file is generated by gcc when compiling with
-                option -ftest-coverage.
-
-
-5. Modules
-==========
-
-Kernel modules may contain cleanup code which is only run during
-module unload time. The gcov mechanism provides a means to collect
-coverage data for such code by keeping a copy of the data associated
-with the unloaded module. This data remains available through debugfs.
-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:
-
-        gcov_persist=0
-
-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
-====================================
-
-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
-cases where the kernel runs on a separate machine, special preparations
-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:
-
-from the source tree:
-  - all C source files + headers
-
-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).
-
-b) gcov is run on the BUILD machine
-
-The following files need to be copied after each test case from test
-to build machine:
-
-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.
-
-Example directory setup on the build machine:
-
-  /tmp/linux:    kernel source tree
-  /tmp/out:      kernel build directory as specified by make O=
-  /tmp/coverage: location of the files copied from the test machine
-
-  [user@build] cd /tmp/out
-  [user@build] gcov -o /tmp/coverage/tmp/out/init main.c
-
-
-7. Troubleshooting
-==================
-
-Problem:  Compilation aborts during linker step.
-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
-          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
-          may not correctly copy files from sysfs.
-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
-
-KSRC=$1
-KOBJ=$2
-DEST=$3
-
-if [ -z "$KSRC" ] || [ -z "$KOBJ" ] || [ -z "$DEST" ]; then
-  echo "Usage: $0 <ksrc directory> <kobj directory> <output.tar.gz>" >&2
-  exit 1
-fi
-
-KSRC=$(cd $KSRC; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
-KOBJ=$(cd $KOBJ; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
-
-find $KSRC $KOBJ \( -name '*.gcno' -o -name '*.[ch]' -o -type l \) -a \
-                 -perm /u+r,g+r | tar cfz $DEST -P -T -
-
-if [ $? -eq 0 ] ; then
-  echo "$DEST successfully created, copy to test system and unpack with:"
-  echo "  tar xfz $DEST -P"
-else
-  echo "Could not create file $DEST"
-fi
-
-
-Appendix B: gather_on_test.sh
-=============================
-
-Sample script to gather coverage data files on the test machine
-(see 6b):
-
-#!/bin/bash -e
-
-DEST=$1
-GCDA=/sys/kernel/debug/gcov
-
-if [ -z "$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"