linux/kernel/gcov/clang.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2019 Google, Inc.
 * modified from kernel/gcov/gcc_4_7.c
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 *
 * LLVM uses profiling data that's deliberately similar to GCC, but has a
 * very different way of exporting that data.  LLVM calls llvm_gcov_init() once
 * per module, and provides a couple of callbacks that we can use to ask for
 * more data.
 *
 * We care about the "writeout" callback, which in turn calls back into
 * compiler-rt/this module to dump all the gathered coverage data to disk:
 *
 *    llvm_gcda_start_file()
 *      llvm_gcda_emit_function()
 *      llvm_gcda_emit_arcs()
 *      llvm_gcda_emit_function()
 *      llvm_gcda_emit_arcs()
 *      [... repeats for each function ...]
 *    llvm_gcda_summary_info()
 *    llvm_gcda_end_file()
 *
 * This design is much more stateless and unstructured than gcc's, and is
 * intended to run at process exit.  This forces us to keep some local state
 * about which module we're dealing with at the moment.  On the other hand, it
 * also means we don't depend as much on how LLVM represents profiling data
 * internally.
 *
 * See LLVM's lib/Transforms/Instrumentation/GCOVProfiling.cpp for more
 * details on how this works, particularly GCOVProfiler::emitProfileArcs(),
 * GCOVProfiler::insertCounterWriteout(), and
 * GCOVProfiler::insertFlush().
 */

#define pr_fmt(fmt) …

#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/printk.h>
#include <linux/ratelimit.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include "gcov.h"

llvm_gcov_callback;

struct gcov_info { … };

struct gcov_fn_info { … };

static struct gcov_info *current_info;

static LIST_HEAD(clang_gcov_list);

void llvm_gcov_init(llvm_gcov_callback writeout, llvm_gcov_callback flush)
{ … }
EXPORT_SYMBOL(…);

void llvm_gcda_start_file(const char *orig_filename, u32 version, u32 checksum)
{ … }
EXPORT_SYMBOL(…);

void llvm_gcda_emit_function(u32 ident, u32 func_checksum, u32 cfg_checksum)
{ … }
EXPORT_SYMBOL(…);

void llvm_gcda_emit_arcs(u32 num_counters, u64 *counters)
{ … }
EXPORT_SYMBOL(…);

void llvm_gcda_summary_info(void)
{ … }
EXPORT_SYMBOL(…);

void llvm_gcda_end_file(void)
{ … }
EXPORT_SYMBOL(…);

/**
 * gcov_info_filename - return info filename
 * @info: profiling data set
 */
const char *gcov_info_filename(struct gcov_info *info)
{ … }

/**
 * gcov_info_version - return info version
 * @info: profiling data set
 */
unsigned int gcov_info_version(struct gcov_info *info)
{ … }

/**
 * gcov_info_next - return next profiling data set
 * @info: profiling data set
 *
 * Returns next gcov_info following @info or first gcov_info in the chain if
 * @info is %NULL.
 */
struct gcov_info *gcov_info_next(struct gcov_info *info)
{ … }

/**
 * gcov_info_link - link/add profiling data set to the list
 * @info: profiling data set
 */
void gcov_info_link(struct gcov_info *info)
{ … }

/**
 * gcov_info_unlink - unlink/remove profiling data set from the list
 * @prev: previous profiling data set
 * @info: profiling data set
 */
void gcov_info_unlink(struct gcov_info *prev, struct gcov_info *info)
{ … }

/**
 * gcov_info_within_module - check if a profiling data set belongs to a module
 * @info: profiling data set
 * @mod: module
 *
 * Returns true if profiling data belongs module, false otherwise.
 */
bool gcov_info_within_module(struct gcov_info *info, struct module *mod)
{ … }

/* Symbolic links to be created for each profiling data file. */
const struct gcov_link gcov_link[] = …;

/**
 * gcov_info_reset - reset profiling data to zero
 * @info: profiling data set
 */
void gcov_info_reset(struct gcov_info *info)
{ … }

/**
 * gcov_info_is_compatible - check if profiling data can be added
 * @info1: first profiling data set
 * @info2: second profiling data set
 *
 * Returns non-zero if profiling data can be added, zero otherwise.
 */
int gcov_info_is_compatible(struct gcov_info *info1, struct gcov_info *info2)
{ … }

/**
 * gcov_info_add - add up profiling data
 * @dest: profiling data set to which data is added
 * @source: profiling data set which is added
 *
 * Adds profiling counts of @source to @dest.
 */
void gcov_info_add(struct gcov_info *dst, struct gcov_info *src)
{ … }

static struct gcov_fn_info *gcov_fn_info_dup(struct gcov_fn_info *fn)
{ … }

/**
 * gcov_info_dup - duplicate profiling data set
 * @info: profiling data set to duplicate
 *
 * Return newly allocated duplicate on success, %NULL on error.
 */
struct gcov_info *gcov_info_dup(struct gcov_info *info)
{ … }

/**
 * gcov_info_free - release memory for profiling data set duplicate
 * @info: profiling data set duplicate to free
 */
void gcov_info_free(struct gcov_info *info)
{ … }

/**
 * convert_to_gcda - convert profiling data set to gcda file format
 * @buffer: the buffer to store file data or %NULL if no data should be stored
 * @info: profiling data set to be converted
 *
 * Returns the number of bytes that were/would have been stored into the buffer.
 */
size_t convert_to_gcda(char *buffer, struct gcov_info *info)
{ … }