Introduction

This page describes how to build and run LTTng(with limited functionality) on Xilnx Zynq Linux.

Overview

The LTTng(Linux Trace Toolkit - next generation) project aims at efficient tracing tools for Linux. LTTng consists of kernel tracer and user tracer, and as a part of project, there are multiple viewers to show and analyze traces. LTTng can trace a lot of kernel functions such as memory, scheduling, filesystem, network, and more.

Requirements

Required modules for LTTng for Xilinx Zynq Linux
  • Xilinx Zynq Linux : Zynq Linux with tracepoints feature(CONFIG_TRACEPOINTS) on
  • LTTng modules : kernel modules for LTTng
  • LTTng tools : userspace daemons and tools
  • userspace rcu : userspace rcu library used by LTTng tools
  • libpopt : used by LTTng tools
Note:
  • Following instructions might need some changes depending on Xilinx Linux Kernel versions.
  • Other kernel options(syscall_tracepoint, perf_events, event_tracing, kprobes, kretprobes) may be turned on to utilize more LTTng features
  • LTTng from this page is running on ramdisk, and /tmp directory is used for build prefix and running path.
  • Userspace tracing(UST) is disabled from LTTng tools due to its dependencies to other libraries

Building Process

Build Directory Hierachy

lttng-build-root /
| - linux-xlnx : Xilinx Zynq Linux for LTTng
| - lttng-modules-xlnx : LTTng kernel modules for Xilinx Zynq linux
| - kos : generated LTTng kernel modules
| - popt-1.16-xlnx : libpopt for LLTng tools
| - userspace-rcu-xlnx : userspace rcu library for LLTng tools
| - lttng-tools-xlnx : LTTng tools

/tmp/<YOUR_LTTNG_ROOT> : the build root directory where all created binaries are placed. (YOUR_LTTNG_ROOT=username-lttng-root for this page)

Building Xilinx Zynq Linux for LTTng

The kernel can be downloaded from Xilinx git,
build > git clone git://github.com/Xilinx/linux-xlnx.git linux-xlnx
build > cd linux-xlnx
The following changes have to be applied,
diff --git a/arch/arm/configs/xilinx_zynq_defconfig b/arch/arm/configs/xilinx_zynq_defconfig
index 58c226e..e9c069c 100644
--- a/arch/arm/configs/xilinx_zynq_defconfig
+++ b/arch/arm/configs/xilinx_zynq_defconfig
@@ -30,7 +30,8 @@ CONFIG_BUILDTIME_EXTABLE_SORT=y
 CONFIG_EXPERIMENTAL=y
 CONFIG_INIT_ENV_ARG_LIMIT=32
 CONFIG_CROSS_COMPILE=""
-CONFIG_LOCALVERSION="-xilinx"
+CONFIG_LOCALVERSION="-xilinx-lttng"
+CONFIG_TRACEPOINTS=y
 CONFIG_LOCALVERSION_AUTO=y
 CONFIG_HAVE_KERNEL_GZIP=y
 CONFIG_HAVE_KERNEL_LZMA=y
diff --git a/arch/arm/mach-zynq/Kconfig b/arch/arm/mach-zynq/Kconfig
index 96e1668..7a557c3 100644
--- a/arch/arm/mach-zynq/Kconfig
+++ b/arch/arm/mach-zynq/Kconfig
@@ -54,3 +54,10 @@ config XILINX_AXIPCIE
 endmenu
 
 endif
+
+config TRACEPOINTS
+       bool "Tracepoints for lttng modules"
+       default y
+       help
+         Enable tracepoints for lttng modules
+
 
Then, the kernel can be configured properly for LTTng using the command below,
build > make ARCH=arm xilinx_zynq_defconfig
Build the kernel by following command,
build > make ARCH=arm uImage UIMAGE_LOADADDR=0x8000
The generated uImage(in arch/arm/boot/) needs to be downloaded into the target ZC702 hardware to run LTTng.
Return to the build root,
build > cd ..

Building LTTng Kernel Modules
The source code can be downloaded by the following command
build > wget https://lttng.org/files/lttng-modules/lttng-modules-2.1.1.tar.bz2
build > tar -xf lttng-modules-2.1.1.tar.bz2
build > cd lttng-modules-2.1.1
For later Linux kernels(3.9 or later), some headers have been changed, so a following change should be applied.
--- /instrumentation/events/lttng-module/sched.h
<span style="font-family: arial,helvetica,sans-serif; line-height: 1.5;">@@ -5,6 +5,7 @@</span>
 #define _TRACE_SCHED_H
 
 #include <linux/sched.h>
+#include <linux/sched/rt.h>
 #include <linux/tracepoint.h>
 
 #ifndef _TRACE_SCHED_DEF_
 
A following change has to be applied, otherwise a huge system call table is included in lttng_tracer.ko which results in vmalloc allocation failure on runtime.
--- /instrumentation/syscalls/headers/arm-32-syscalls-2.6.38_integers_override.h
@@ -2,7 +2,6 @@
 
 #define OVERRIDE_TABLE_32_sys_arm_fadvise64_64
 #define OVERRIDE_TABLE_32_sys_sync_file_range2
-#define OVERRIDE_TABLE_32_sys_set_tls
 
 #ifndef CREATE_SYSCALL_TABLE
 
@@ -38,18 +37,6 @@ SC_TRACE_EVENT(sys_sync_file_range2,
        TP_printk()
 )
 
-SC_TRACE_EVENT(sys_set_tls,
-       TP_PROTO(unsigned int tid, unsigned long tls),
-       TP_ARGS(tid, tls),
-       TP_STRUCT__entry(
-               __field(unsigned int, tid)
-               __field_hex(unsigned int, tls)),
-       TP_fast_assign(
-               tp_assign(tid, tid)
-               tp_assign(tls, tls)),
-       TP_printk()
-)
-
 #else  /* CREATE_SYSCALL_TABLE */
 
 #define OVVERRIDE_TABLE_32_sys_mmap
@@ -59,9 +46,6 @@ TRACE_SYSCALL_TABLE(sys_mmap, sys_mmap, 90, 6)
 TRACE_SYSCALL_TABLE(sys_arm_fadvise64_64, sys_arm_fadvise64_64, 270, 4)
 #define OVERRIDE_TABLE_32_sys_sync_file_range2
 TRACE_SYSCALL_TABLE(sys_sync_file_range2, sys_sync_file_range2, 341, 4)
-#define OVERRIDE_TABLE_32_sys_set_tls
-TRACE_SYSCALL_TABLE(sys_set_tls, sys_set_tls, 0xf0005, 2)
-
 
 #endif /* CREATE_SYSCALL_TABLE */
KERNELDIR should be set to the Linux kernel directory used above, and the LTTng modules can be build as following,
build > make KERNELDIR=lttng-build-root/linux-xlnx ARCH=arm
Since ramdisk doesn't have proper directories for kernel modules, collect all LTTng kernel modules into one directory,
build > mkdir lttng-build-root/kos
build > find . -name "*.ko" -exec cp -i {} lttng-build-root/kos/. \;
Return to the build root,
build > cd ..

Building libpopt for LTTng Tools
libpopt and userspace rcu should be built before building LTTng tools.
libpopt can be downloaded from the following link,
build > wget http://rpm5.org/files/popt/popt-1.16.tar.gz
build > tar -xf popt-1.16.tar.gz
build > cd popt-1.16
libpopt needs to be configured and installed as following,
build > ./configure --prefix=/tmp/username-lttng-root/ --host=arm-xilinx-linux-gnueabi
build > make install
Return to the build root,
build > cd ..

Building userspace rcu library for LTTng tools
Userspace rcu can be downloaded using the command show below
build > wget https://lttng.org/files/urcu/userspace-rcu-0.7.6.tar.bz2
build > tar -xf userspace-rcu-0.7.6.tar.bz2
build > cd userspace-rcu-0.7.6
Userspace rcu needs to be configured in the similar way to libpopt,
build > ./configure --prefix=/tmp/username-lttng-root/ --host=arm-xilinx-linux-gnueabi
Following changes should be applied to config.h to correct the configuration. (this is a workaround)
+++ config.h
 
@@ -45,7 +45,7 @@
/* Define to 1 if your system has a GNU libc compatible `malloc' function, and
to 0 otherwise. */
-#define HAVE_MALLOC 0
+#define HAVE_MALLOC 1
/* Define to 1 if you have the <memory.h> header file. */
#define HAVE_MEMORY_H 1
@@ -136,7 +136,7 @@
#endif
/* Define to rpl_malloc if the replacement function should be used. */
-#define malloc rpl_malloc
+/*#define malloc rpl_malloc*/
/* Define to `int' if <sys/types.h> does not define. */
/* #undef pid_t */
Now, userspace rcu can be built and installed simply using following,
build > make install
Return to the build root,
build > cd ..

Building LTTng Tools
Since all dependent libraries are built, LTTng tools can be built upon those. The source tree can be downloaded by the following command,
build > wget https://lttng.org/files/lttng-tools/lttng-tools-2.1.1.tar.bz2
build > tar -xf lttng-tools-2.1.1.tar.bz2
build > cd lttng-tools-2.1.1
LTTng tools should be configured following, and as mentioned earlier, userspace tracing(UST) needs to be disabled due to complex dependencies. -DXILINX_MOD is used for modifications
build > ./configure --prefix=/tmp/username-lttng-root/ --host=arm-xilinx-linux-gnueabi LDFLAGS=-L/tmp/username-lttng-root/lib CPPFLAGS="-I/tmp/username-lttng-root/include -DXILINX_MOD" --disable-lttng-ust
Because this LTTng on Zynq is running on the ramdisk, its running path has to be reconfigured, and that can be done with the following change,
+++ src/common/defaults.h
 
@@ -32,8 +32,13 @@
 /* Environment variable to set session daemon binary path. */
 #define DEFAULT_SESSIOND_PATH_ENV               "LTTNG_SESSIOND_PATH"
 
+#ifdef XILINX_MOD
+/* Default trace output directory name */
+#define DEFAULT_TRACE_DIR_NAME                  "/tmp/lttng-traces"
+#else
 /* Default trace output directory name */
 #define DEFAULT_TRACE_DIR_NAME                  "lttng-traces"
+#endif
 
 /* Default size of a hash table */
 #define DEFAULT_HT_SIZE                         4
@@ -77,7 +82,11 @@
 
 
 /* Default lttng run directory */
+#ifdef XILINX_MOD
+#define DEFAULT_LTTNG_RUNDIR                    "/tmp/lttng"
+#else
 #define DEFAULT_LTTNG_RUNDIR                    "/var/run/lttng"
+#endif
 #define DEFAULT_LTTNG_HOME_RUNDIR               "%s/.lttng"
 #define DEFAULT_LTTNG_SESSIOND_PIDFILE          "lttng-sessiond.pid"
Build and install LTTng tools using the following command,
build > make install
Return to the build root,
build > cd ..
Now all needed libraries and executable are built and installed in /tmp/<YOUR_LTTNG_ROOT>/. <YOUR_LTTNG_ROOT> directory should be placed in the /tmp/ on the target Zynq Linux.

Running Process

Running LTTng on Xilinx Zynq Linux

Make sure its the kernel built from previous steps by checking if its uname is '3.6.0-linux-xilinx-lttng-dirty',
zynq > uname -r
3.6.0-linux-xilinx-lttng-dirty
LTTng kernel modules need to be loaded in order to run LTTng tools. The modprobe directory should be created for not getting modprobe errors as a workaround. The proper directory can be created using the following command,
zynq > mkdir -p /lib/modules/$(uname -r)
Place all LTTng kernel modules in lttng-build/root/kos in the modprobe directory created above. Now LTTng tools can run without problem. More details operations can be found on the offical website(https://lttng.org/), and the simple operation will be described here as an example.
A LTTng session needs to be created,
zynq > /tmp/username-lttng-root/bin/lttng create <YOUR_SESSION>
Available kernel events can be listed by following,
zynq > /tmp/username-lttng-root/bin/lttng list -k
All kernel events can be enabled using the following command,
zynq > /tmp/username-lttng-root/bin/lttng enable-event -k -a
Tracing is started and stopped by commands shown below,
zynq > /tmp/username-lttng-root/bin/lttng start
zynq > /tmp/username-lttng-root/bin/lttng stop
The current LTTng session can be destroyed by following,
zynq > /tmp/username-lttng-root/bin/lttng destroy

Viewing LTTng Traces

All traces are stored in /tmp/lttng-traces/<YOUR_SESSION_DIR>, and traces can be viewed and analyzed using several viewers. For example, Eclipse with LTTng plugin can be downloaded and used as a LTTng viewer(https://lttng.org/eclipse). Detailed instructions for LTTng viewers are available on the official website(https://lttng.org/viewers)

External Link