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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().
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190417225328.208129-1-trong@android.com
Signed-off-by: Greg Hackmann <ghackmann@android.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Tri Vo <trong@android.com>
Co-developed-by: Nick Desaulniers <ndesaulniers@google.com>
Co-developed-by: Tri Vo <trong@android.com>
Tested-by: Trilok Soni <tsoni@quicinc.com>
Tested-by: Prasad Sodagudi <psodagud@quicinc.com>
Tested-by: Tri Vo <trong@android.com>
Tested-by: Daniel Mentz <danielmentz@google.com>
Tested-by: Petri Gynther <pgynther@google.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
90 lines
2.2 KiB
C
90 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This code maintains a list of active profiling data structures.
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*
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* Copyright IBM Corp. 2009
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* Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
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*
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* Uses gcc-internal data definitions.
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* Based on the gcov-kernel patch by:
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* Hubertus Franke <frankeh@us.ibm.com>
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* Nigel Hinds <nhinds@us.ibm.com>
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* Rajan Ravindran <rajancr@us.ibm.com>
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* Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
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* Paul Larson
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*/
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#define pr_fmt(fmt) "gcov: " fmt
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/sched.h>
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#include "gcov.h"
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int gcov_events_enabled;
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DEFINE_MUTEX(gcov_lock);
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/**
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* gcov_enable_events - enable event reporting through gcov_event()
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*
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* Turn on reporting of profiling data load/unload-events through the
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* gcov_event() callback. Also replay all previous events once. This function
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* is needed because some events are potentially generated too early for the
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* callback implementation to handle them initially.
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*/
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void gcov_enable_events(void)
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{
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struct gcov_info *info = NULL;
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mutex_lock(&gcov_lock);
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gcov_events_enabled = 1;
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/* Perform event callback for previously registered entries. */
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while ((info = gcov_info_next(info))) {
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gcov_event(GCOV_ADD, info);
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cond_resched();
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}
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mutex_unlock(&gcov_lock);
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}
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#ifdef CONFIG_MODULES
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/* Update list and generate events when modules are unloaded. */
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static int gcov_module_notifier(struct notifier_block *nb, unsigned long event,
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void *data)
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{
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struct module *mod = data;
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struct gcov_info *info = NULL;
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struct gcov_info *prev = NULL;
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if (event != MODULE_STATE_GOING)
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return NOTIFY_OK;
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mutex_lock(&gcov_lock);
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/* Remove entries located in module from linked list. */
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while ((info = gcov_info_next(info))) {
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if (gcov_info_within_module(info, mod)) {
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gcov_info_unlink(prev, info);
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if (gcov_events_enabled)
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gcov_event(GCOV_REMOVE, info);
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} else
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prev = info;
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}
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mutex_unlock(&gcov_lock);
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return NOTIFY_OK;
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}
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static struct notifier_block gcov_nb = {
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.notifier_call = gcov_module_notifier,
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};
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static int __init gcov_init(void)
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{
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return register_module_notifier(&gcov_nb);
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}
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device_initcall(gcov_init);
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#endif /* CONFIG_MODULES */
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