src/arch/arm/linux/fs_workload.cc - public/gem5 - Git at Google

 /*
  * Copyright (c) 2010-2013, 2016, 2020 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Copyright (c) 2002-2006 The Regents of The University of Michigan
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met: redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer;
  * redistributions in binary form must reproduce the above copyright
  * notice, this list of conditions and the following disclaimer in the
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "arch/arm/linux/fs_workload.hh"

 #include "arch/arm/linux/atag.hh"
 #include "arch/arm/system.hh"
 #include "arch/arm/utility.hh"
 #include "arch/generic/linux/threadinfo.hh"
 #include "base/loader/dtb_file.hh"
 #include "base/loader/object_file.hh"
 #include "base/loader/symtab.hh"
 #include "cpu/base.hh"
 #include "cpu/pc_event.hh"
 #include "cpu/thread_context.hh"
 #include "debug/Loader.hh"
 #include "kern/linux/events.hh"
 #include "kern/linux/helpers.hh"
 #include "kern/system_events.hh"
 #include "mem/physical.hh"
 #include "sim/stat_control.hh"

 namespace gem5
 {

 using namespace linux;

 namespace ArmISA
 {

 FsLinux::FsLinux(const Params &p) : ArmISA::FsWorkload(p),
     enableContextSwitchStatsDump(p.enable_context_switch_stats_dump)
 {}

 void
 FsLinux::initState()
 {
     ArmISA::FsWorkload::initState();

     // Load symbols at physical address, we might not want
     // to do this permanently, for but early bootup work
     // it is helpful.
     if (params().early_kernel_symbols) {
         auto phys_globals = kernelObj->symtab().globals()->mask(_loadAddrMask);
         kernelSymtab.insert(*phys_globals);
         loader::debugSymbolTable.insert(*phys_globals);
     }

     // Setup boot data structure
     // Check if the kernel image has a symbol that tells us it supports
     // device trees.
     bool kernel_has_fdt_support =
         kernelSymtab.find("unflatten_device_tree") != kernelSymtab.end();
     bool dtb_file_specified = params().dtb_filename != "";

     if (kernel_has_fdt_support && dtb_file_specified) {
         // Kernel supports flattened device tree and dtb file specified.
         // Using Device Tree Blob to describe system configuration.
         inform("Loading DTB file: %s at address %#x\n", params().dtb_filename,
                 params().dtb_addr);

         auto *dtb_file = new loader::DtbFile(params().dtb_filename);

         if (!dtb_file->addBootCmdLine(
                     commandLine.c_str(), commandLine.size())) {
             warn("couldn't append bootargs to DTB file: %s\n",
                  params().dtb_filename);
         }

         dtb_file->buildImage().offset(params().dtb_addr)
             .write(system->physProxy);
         delete dtb_file;
     } else {
         // Using ATAGS
         // Warn if the kernel supports FDT and we haven't specified one
         if (kernel_has_fdt_support) {
             assert(!dtb_file_specified);
             warn("Kernel supports device tree, but no DTB file specified\n");
         }
         // Warn if the kernel doesn't support FDT and we have specified one
         if (dtb_file_specified) {
             assert(!kernel_has_fdt_support);
             warn("DTB file specified, but no device tree support in kernel\n");
         }

         AtagCore ac;
         ac.flags(1); // read-only
         ac.pagesize(8192);
         ac.rootdev(0);

         AddrRangeList atagRanges = system->getPhysMem().getConfAddrRanges();
         fatal_if(atagRanges.size() != 1,
                  "Expected a single ATAG memory entry but got %d",
                  atagRanges.size());
         AtagMem am;
         am.memSize(atagRanges.begin()->size());
         am.memStart(atagRanges.begin()->start());

         AtagCmdline ad;
         ad.cmdline(commandLine);

         DPRINTF(Loader, "boot command line %d bytes: %s\n",
                 ad.size() << 2, commandLine);

         AtagNone an;

         uint32_t size = ac.size() + am.size() + ad.size() + an.size();
         uint32_t offset = 0;
         uint8_t *boot_data = new uint8_t[size << 2];

         offset += ac.copyOut(boot_data + offset);
         offset += am.copyOut(boot_data + offset);
         offset += ad.copyOut(boot_data + offset);
         offset += an.copyOut(boot_data + offset);

         DPRINTF(Loader, "Boot atags was %d bytes in total\n", size << 2);
         DDUMP(Loader, boot_data, size << 2);

         system->physProxy.writeBlob(params().dtb_addr,
                                     boot_data, size << 2);

         delete[] boot_data;
     }

     if (getArch() == loader::Arm64) {
         // We inform the bootloader of the kernel entry point. This was added
         // originally done because the entry offset changed in kernel v5.8.
         // Previously the bootloader just used a hardcoded address.
         for (auto *tc: system->threads) {
             tc->setIntReg(0, params().dtb_addr);
             tc->setIntReg(5, params().cpu_release_addr);
         }
     } else {
         // Kernel boot requirements to set up r0, r1 and r2 in ARMv7
         for (auto *tc: system->threads) {
             tc->setIntReg(0, 0);
             tc->setIntReg(1, params().machine_type);
             tc->setIntReg(2, params().dtb_addr);
         }
     }
 }

 FsLinux::~FsLinux()
 {
     delete debugPrintk;
     delete skipUDelay;
     delete skipConstUDelay;
     delete kernelOops;
     delete kernelPanic;

     delete dumpStats;
 }

 void
 FsLinux::startup()
 {
     FsWorkload::startup();

     if (enableContextSwitchStatsDump) {
         if (getArch() == loader::Arm64)
             dumpStats = addKernelFuncEvent<DumpStats64>("__switch_to");
         else
             dumpStats = addKernelFuncEvent<DumpStats>("__switch_to");

         panic_if(!dumpStats, "dumpStats not created!");

         std::string task_filename = "tasks.txt";
         taskFile = simout.create(name() + "." + task_filename);

         for (auto *tc: system->threads) {
             uint32_t pid = tc->getCpuPtr()->getPid();
             if (pid != BaseCPU::invldPid) {
                 mapPid(tc, pid);
                 tc->getCpuPtr()->taskId(taskMap[pid]);
             }
         }
     }

     const std::string dmesg_output = name() + ".dmesg";
     if (params().panic_on_panic) {
         kernelPanic = addKernelFuncEventOrPanic<linux::KernelPanic>(
             "panic", "Kernel panic in simulated kernel", dmesg_output);
     } else {
         kernelPanic = addKernelFuncEventOrPanic<linux::DmesgDump>(
             "panic", "Kernel panic in simulated kernel", dmesg_output);
     }

     if (params().panic_on_oops) {
         kernelOops = addKernelFuncEventOrPanic<linux::KernelPanic>(
             "oops_exit", "Kernel oops in guest", dmesg_output);
     } else {
         kernelOops = addKernelFuncEventOrPanic<linux::DmesgDump>(
             "oops_exit", "Kernel oops in guest", dmesg_output);
     }

     // With ARM udelay() is #defined to __udelay
     // newer kernels use __loop_udelay and __loop_const_udelay symbols
     skipUDelay = addSkipFunc<SkipUDelay>(
         "__loop_udelay", "__udelay", 1000, 0);
     if (!skipUDelay) {
         skipUDelay = addSkipFuncOrPanic<SkipUDelay>(
                 "__udelay", "__udelay", 1000, 0);
     }

     // constant arguments to udelay() have some precomputation done ahead of
     // time. Constant comes from code.
     skipConstUDelay = addSkipFunc<SkipUDelay>(
         "__loop_const_udelay", "__const_udelay", 1000, 107374);
     if (!skipConstUDelay) {
         skipConstUDelay = addSkipFuncOrPanic<SkipUDelay>(
             "__const_udelay", "__const_udelay", 1000, 107374);
     }

     debugPrintk = addSkipFunc<DebugPrintk>("dprintk");
 }

 void
 FsLinux::mapPid(ThreadContext *tc, uint32_t pid)
 {
     // Create a new unique identifier for this pid
     std::map<uint32_t, uint32_t>::iterator itr = taskMap.find(pid);
     if (itr == taskMap.end()) {
         uint32_t map_size = taskMap.size();
         if (map_size > context_switch_task_id::MaxNormalTaskId + 1) {
             warn_once("Error out of identifiers for cache occupancy stats");
             taskMap[pid] = context_switch_task_id::Unknown;
         } else {
             taskMap[pid] = map_size;
         }
     }
 }

 void
 FsLinux::dumpDmesg()
 {
     linux::dumpDmesg(system->threads[0], std::cout);
 }

 /**
  * Extracts the information used by the DumpStatsPCEvent by reading the
  * thread_info pointer passed to __switch_to() in 32 bit ARM Linux
  *
  *  r0 = task_struct of the previously running process
  *  r1 = thread_info of the previously running process
  *  r2 = thread_info of the next process to run
  */
 void
 DumpStats::getTaskDetails(ThreadContext *tc, uint32_t &pid,
     uint32_t &tgid, std::string &next_task_str, int32_t &mm) {

     linux::ThreadInfo ti(tc);
     Addr task_descriptor = tc->readIntReg(2);
     pid = ti.curTaskPID(task_descriptor);
     tgid = ti.curTaskTGID(task_descriptor);
     next_task_str = ti.curTaskName(task_descriptor);

     // Streamline treats pid == -1 as the kernel process.
     // Also pid == 0 implies idle process (except during Linux boot)
     mm = ti.curTaskMm(task_descriptor);
 }

 /**
  * Extracts the information used by the DumpStatsPCEvent64 by reading the
  * task_struct pointer passed to __switch_to() in 64 bit ARM Linux
  *
  *  r0 = task_struct of the previously running process
  *  r1 = task_struct of next process to run
  */
 void
 DumpStats64::getTaskDetails(ThreadContext *tc, uint32_t &pid,
     uint32_t &tgid, std::string &next_task_str, int32_t &mm) {

     linux::ThreadInfo ti(tc);
     Addr task_struct = tc->readIntReg(1);
     pid = ti.curTaskPIDFromTaskStruct(task_struct);
     tgid = ti.curTaskTGIDFromTaskStruct(task_struct);
     next_task_str = ti.curTaskNameFromTaskStruct(task_struct);

     // Streamline treats pid == -1 as the kernel process.
     // Also pid == 0 implies idle process (except during Linux boot)
     mm = ti.curTaskMmFromTaskStruct(task_struct);
 }

 /** This function is called whenever the the kernel function
  *  "__switch_to" is called to change running tasks.
  */
 void
 DumpStats::process(ThreadContext *tc)
 {
     uint32_t pid = 0;
     uint32_t tgid = 0;
     std::string next_task_str;
     int32_t mm = 0;

     getTaskDetails(tc, pid, tgid, next_task_str, mm);

     bool is_kernel = (mm == 0);
     if (is_kernel && (pid != 0)) {
         pid = -1;
         tgid = -1;
         next_task_str = "kernel";
     }

     FsLinux* wl = dynamic_cast<FsLinux *>(tc->getSystemPtr()->workload);
     panic_if(!wl, "System workload is not ARM Linux!");
     std::map<uint32_t, uint32_t>& taskMap = wl->taskMap;

     // Create a new unique identifier for this pid
     wl->mapPid(tc, pid);

     // Set cpu task id, output process info, and dump stats
     tc->getCpuPtr()->taskId(taskMap[pid]);
     tc->getCpuPtr()->setPid(pid);

     OutputStream* taskFile = wl->taskFile;

     // Task file is read by cache occupancy plotting script or
     // Streamline conversion script.
     ccprintf(*(taskFile->stream()),
              "tick=%lld %d cpu_id=%d next_pid=%d next_tgid=%d next_task=%s\n",
              curTick(), taskMap[pid], tc->cpuId(), (int)pid, (int)tgid,
              next_task_str);
     taskFile->stream()->flush();

     // Dump and reset statistics
     statistics::schedStatEvent(true, true, curTick(), 0);
 }

 } // namespace ArmISA
 } // namespace gem5
	/*
	* Copyright (c) 2010-2013, 2016, 2020 ARM Limited
	* All rights reserved
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Copyright (c) 2002-2006 The Regents of The University of Michigan
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met: redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer;
	* redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "arch/arm/linux/fs_workload.hh"

	#include "arch/arm/linux/atag.hh"
	#include "arch/arm/system.hh"
	#include "arch/arm/utility.hh"
	#include "arch/generic/linux/threadinfo.hh"
	#include "base/loader/dtb_file.hh"
	#include "base/loader/object_file.hh"
	#include "base/loader/symtab.hh"
	#include "cpu/base.hh"
	#include "cpu/pc_event.hh"
	#include "cpu/thread_context.hh"
	#include "debug/Loader.hh"
	#include "kern/linux/events.hh"
	#include "kern/linux/helpers.hh"
	#include "kern/system_events.hh"
	#include "mem/physical.hh"
	#include "sim/stat_control.hh"

	namespace gem5
	{

	using namespace linux;

	namespace ArmISA
	{

	FsLinux::FsLinux(const Params &p) : ArmISA::FsWorkload(p),
	enableContextSwitchStatsDump(p.enable_context_switch_stats_dump)
	{}

	void
	FsLinux::initState()
	{
	ArmISA::FsWorkload::initState();

	// Load symbols at physical address, we might not want
	// to do this permanently, for but early bootup work
	// it is helpful.
	if (params().early_kernel_symbols) {
	auto phys_globals = kernelObj->symtab().globals()->mask(_loadAddrMask);
	kernelSymtab.insert(*phys_globals);
	loader::debugSymbolTable.insert(*phys_globals);
	}

	// Setup boot data structure
	// Check if the kernel image has a symbol that tells us it supports
	// device trees.
	bool kernel_has_fdt_support =
	kernelSymtab.find("unflatten_device_tree") != kernelSymtab.end();
	bool dtb_file_specified = params().dtb_filename != "";

	if (kernel_has_fdt_support && dtb_file_specified) {
	// Kernel supports flattened device tree and dtb file specified.
	// Using Device Tree Blob to describe system configuration.
	inform("Loading DTB file: %s at address %#x\n", params().dtb_filename,
	params().dtb_addr);

	auto *dtb_file = new loader::DtbFile(params().dtb_filename);

	if (!dtb_file->addBootCmdLine(
	commandLine.c_str(), commandLine.size())) {
	warn("couldn't append bootargs to DTB file: %s\n",
	params().dtb_filename);
	}

	dtb_file->buildImage().offset(params().dtb_addr)
	.write(system->physProxy);
	delete dtb_file;
	} else {
	// Using ATAGS
	// Warn if the kernel supports FDT and we haven't specified one
	if (kernel_has_fdt_support) {
	assert(!dtb_file_specified);
	warn("Kernel supports device tree, but no DTB file specified\n");
	}
	// Warn if the kernel doesn't support FDT and we have specified one
	if (dtb_file_specified) {
	assert(!kernel_has_fdt_support);
	warn("DTB file specified, but no device tree support in kernel\n");
	}

	AtagCore ac;
	ac.flags(1); // read-only
	ac.pagesize(8192);
	ac.rootdev(0);

	AddrRangeList atagRanges = system->getPhysMem().getConfAddrRanges();
	fatal_if(atagRanges.size() != 1,
	"Expected a single ATAG memory entry but got %d",
	atagRanges.size());
	AtagMem am;
	am.memSize(atagRanges.begin()->size());
	am.memStart(atagRanges.begin()->start());

	AtagCmdline ad;
	ad.cmdline(commandLine);

	DPRINTF(Loader, "boot command line %d bytes: %s\n",
	ad.size() << 2, commandLine);

	AtagNone an;

	uint32_t size = ac.size() + am.size() + ad.size() + an.size();
	uint32_t offset = 0;
	uint8_t *boot_data = new uint8_t[size << 2];

	offset += ac.copyOut(boot_data + offset);
	offset += am.copyOut(boot_data + offset);
	offset += ad.copyOut(boot_data + offset);
	offset += an.copyOut(boot_data + offset);

	DPRINTF(Loader, "Boot atags was %d bytes in total\n", size << 2);
	DDUMP(Loader, boot_data, size << 2);

	system->physProxy.writeBlob(params().dtb_addr,
	boot_data, size << 2);

	delete[] boot_data;
	}

	if (getArch() == loader::Arm64) {
	// We inform the bootloader of the kernel entry point. This was added
	// originally done because the entry offset changed in kernel v5.8.
	// Previously the bootloader just used a hardcoded address.
	for (auto *tc: system->threads) {
	tc->setIntReg(0, params().dtb_addr);
	tc->setIntReg(5, params().cpu_release_addr);
	}
	} else {
	// Kernel boot requirements to set up r0, r1 and r2 in ARMv7
	for (auto *tc: system->threads) {
	tc->setIntReg(0, 0);
	tc->setIntReg(1, params().machine_type);
	tc->setIntReg(2, params().dtb_addr);
	}
	}
	}

	FsLinux::~FsLinux()
	{
	delete debugPrintk;
	delete skipUDelay;
	delete skipConstUDelay;
	delete kernelOops;
	delete kernelPanic;

	delete dumpStats;
	}

	void
	FsLinux::startup()
	{
	FsWorkload::startup();

	if (enableContextSwitchStatsDump) {
	if (getArch() == loader::Arm64)
	dumpStats = addKernelFuncEvent<DumpStats64>("__switch_to");
	else
	dumpStats = addKernelFuncEvent<DumpStats>("__switch_to");

	panic_if(!dumpStats, "dumpStats not created!");

	std::string task_filename = "tasks.txt";
	taskFile = simout.create(name() + "." + task_filename);

	for (auto *tc: system->threads) {
	uint32_t pid = tc->getCpuPtr()->getPid();
	if (pid != BaseCPU::invldPid) {
	mapPid(tc, pid);
	tc->getCpuPtr()->taskId(taskMap[pid]);
	}
	}
	}

	const std::string dmesg_output = name() + ".dmesg";
	if (params().panic_on_panic) {
	kernelPanic = addKernelFuncEventOrPanic<linux::KernelPanic>(
	"panic", "Kernel panic in simulated kernel", dmesg_output);
	} else {
	kernelPanic = addKernelFuncEventOrPanic<linux::DmesgDump>(
	"panic", "Kernel panic in simulated kernel", dmesg_output);
	}

	if (params().panic_on_oops) {
	kernelOops = addKernelFuncEventOrPanic<linux::KernelPanic>(
	"oops_exit", "Kernel oops in guest", dmesg_output);
	} else {
	kernelOops = addKernelFuncEventOrPanic<linux::DmesgDump>(
	"oops_exit", "Kernel oops in guest", dmesg_output);
	}

	// With ARM udelay() is #defined to __udelay
	// newer kernels use __loop_udelay and __loop_const_udelay symbols
	skipUDelay = addSkipFunc<SkipUDelay>(
	"__loop_udelay", "__udelay", 1000, 0);
	if (!skipUDelay) {
	skipUDelay = addSkipFuncOrPanic<SkipUDelay>(
	"__udelay", "__udelay", 1000, 0);
	}

	// constant arguments to udelay() have some precomputation done ahead of
	// time. Constant comes from code.
	skipConstUDelay = addSkipFunc<SkipUDelay>(
	"__loop_const_udelay", "__const_udelay", 1000, 107374);
	if (!skipConstUDelay) {
	skipConstUDelay = addSkipFuncOrPanic<SkipUDelay>(
	"__const_udelay", "__const_udelay", 1000, 107374);
	}

	debugPrintk = addSkipFunc<DebugPrintk>("dprintk");
	}

	void
	FsLinux::mapPid(ThreadContext *tc, uint32_t pid)
	{
	// Create a new unique identifier for this pid
	std::map<uint32_t, uint32_t>::iterator itr = taskMap.find(pid);
	if (itr == taskMap.end()) {
	uint32_t map_size = taskMap.size();
	if (map_size > context_switch_task_id::MaxNormalTaskId + 1) {
	warn_once("Error out of identifiers for cache occupancy stats");
	taskMap[pid] = context_switch_task_id::Unknown;
	} else {
	taskMap[pid] = map_size;
	}
	}
	}

	void
	FsLinux::dumpDmesg()
	{
	linux::dumpDmesg(system->threads[0], std::cout);
	}

	/**
	* Extracts the information used by the DumpStatsPCEvent by reading the
	* thread_info pointer passed to __switch_to() in 32 bit ARM Linux
	*
	* r0 = task_struct of the previously running process
	* r1 = thread_info of the previously running process
	* r2 = thread_info of the next process to run
	*/
	void
	DumpStats::getTaskDetails(ThreadContext *tc, uint32_t &pid,
	uint32_t &tgid, std::string &next_task_str, int32_t &mm) {

	linux::ThreadInfo ti(tc);
	Addr task_descriptor = tc->readIntReg(2);
	pid = ti.curTaskPID(task_descriptor);
	tgid = ti.curTaskTGID(task_descriptor);
	next_task_str = ti.curTaskName(task_descriptor);

	// Streamline treats pid == -1 as the kernel process.
	// Also pid == 0 implies idle process (except during Linux boot)
	mm = ti.curTaskMm(task_descriptor);
	}

	/**
	* Extracts the information used by the DumpStatsPCEvent64 by reading the
	* task_struct pointer passed to __switch_to() in 64 bit ARM Linux
	*
	* r0 = task_struct of the previously running process
	* r1 = task_struct of next process to run
	*/
	void
	DumpStats64::getTaskDetails(ThreadContext *tc, uint32_t &pid,
	uint32_t &tgid, std::string &next_task_str, int32_t &mm) {

	linux::ThreadInfo ti(tc);
	Addr task_struct = tc->readIntReg(1);
	pid = ti.curTaskPIDFromTaskStruct(task_struct);
	tgid = ti.curTaskTGIDFromTaskStruct(task_struct);
	next_task_str = ti.curTaskNameFromTaskStruct(task_struct);

	// Streamline treats pid == -1 as the kernel process.
	// Also pid == 0 implies idle process (except during Linux boot)
	mm = ti.curTaskMmFromTaskStruct(task_struct);
	}

	/** This function is called whenever the the kernel function
	* "__switch_to" is called to change running tasks.
	*/
	void
	DumpStats::process(ThreadContext *tc)
	{
	uint32_t pid = 0;
	uint32_t tgid = 0;
	std::string next_task_str;
	int32_t mm = 0;

	getTaskDetails(tc, pid, tgid, next_task_str, mm);

	bool is_kernel = (mm == 0);
	if (is_kernel && (pid != 0)) {
	pid = -1;
	tgid = -1;
	next_task_str = "kernel";
	}

	FsLinux* wl = dynamic_cast<FsLinux *>(tc->getSystemPtr()->workload);
	panic_if(!wl, "System workload is not ARM Linux!");
	std::map<uint32_t, uint32_t>& taskMap = wl->taskMap;

	// Create a new unique identifier for this pid
	wl->mapPid(tc, pid);

	// Set cpu task id, output process info, and dump stats
	tc->getCpuPtr()->taskId(taskMap[pid]);
	tc->getCpuPtr()->setPid(pid);

	OutputStream* taskFile = wl->taskFile;

	// Task file is read by cache occupancy plotting script or
	// Streamline conversion script.
	ccprintf(*(taskFile->stream()),
	"tick=%lld %d cpu_id=%d next_pid=%d next_tgid=%d next_task=%s\n",
	curTick(), taskMap[pid], tc->cpuId(), (int)pid, (int)tgid,
	next_task_str);
	taskFile->stream()->flush();

	// Dump and reset statistics
	statistics::schedStatEvent(true, true, curTick(), 0);
	}

	} // namespace ArmISA
	} // namespace gem5