Date:   Tue, 21 Dec 2021 17:40:10 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Leo Yan <leo.yan@linaro.org>
Cc:     carsten.haitzler@foss.arm.com, linux-kernel@vger.kernel.org,
        coresight@lists.linaro.org, suzuki.poulose@arm.com,
        mathieu.poirier@linaro.org, mike.leach@linaro.org,
        inux-perf-users@vger.kernel.org
Subject: Re: [PATCH 04/12] perf test: Add beginning of test infra + test to
 exercise coresight
Message-ID: <YcI7qrNz47iIhzYM@kernel.org>
References: <20211215160403.69264-1-carsten.haitzler@foss.arm.com>
 <20211215160403.69264-4-carsten.haitzler@foss.arm.com>
 <20211221150349.GB41974@leoy-ThinkPad-X240s>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20211221150349.GB41974@leoy-ThinkPad-X240s>
Precedence: bulk

Em Tue, Dec 21, 2021 at 11:03:49PM +0800, Leo Yan escreveu:
> Hi Carsten,
> 
> On Wed, Dec 15, 2021 at 04:03:55PM +0000, carsten.haitzler@foss.arm.com wrote:
> > From: Carsten Haitzler <carsten.haitzler@arm.com>
> > 
> > This adds the initial test harness to run perf record and examine the
> > resuling output when coresight is enabled on arm64 and check the
> > resulting quality of the output as part of perf test.
> > 
> > Signed-off-by: Carsten Haitzler <carsten.haitzler@arm.com>
> > ---
> >  MAINTAINERS                                   |   3 +
> >  tools/perf/Makefile.perf                      |  14 +-
> >  .../tests/shell/coresight_asm_pure_loop.sh    |  18 +++
> >  tools/perf/tests/shell/lib/coresight.sh       | 130 ++++++++++++++++++
> >  tools/perf/tests/shell/tools/Makefile         |  26 ++++
> >  .../perf/tests/shell/tools/coresight/Makefile |  27 ++++
> >  .../shell/tools/coresight/Makefile.miniconfig |  23 ++++
> >  .../tools/coresight/asm_pure_loop/Makefile    |  30 ++++
> >  .../coresight/asm_pure_loop/asm_pure_loop.S   |  28 ++++
> >  9 files changed, 297 insertions(+), 2 deletions(-)
> >  create mode 100755 tools/perf/tests/shell/coresight_asm_pure_loop.sh
> >  create mode 100644 tools/perf/tests/shell/lib/coresight.sh
> >  create mode 100644 tools/perf/tests/shell/tools/Makefile
> >  create mode 100644 tools/perf/tests/shell/tools/coresight/Makefile
> >  create mode 100644 tools/perf/tests/shell/tools/coresight/Makefile.miniconfig
> >  create mode 100644 tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile
> >  create mode 100644 tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S
> 
> The folder naming is okay for me, but it is cyclic with the format:
> "tools/.../tools/".  So I am wandering if below two pathes are better?
> 
>   tools/perf/tests/shell/prog/coresight/
>   or
>   tools/perf/tests/shell/coresight/

The later, its descriptive enough, I think, and the shortest variant so
far.

- Arnaldo
 
> I'd like to leave this question for Arnaldo / Jiri for the folder
> layout.
> 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 13f9a84a617e..d46e8469c467 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -1894,6 +1894,9 @@ F:	tools/perf/arch/arm/util/auxtrace.c
> >  F:	tools/perf/arch/arm/util/cs-etm.c
> >  F:	tools/perf/arch/arm/util/cs-etm.h
> >  F:	tools/perf/arch/arm/util/pmu.c
> > +F:	tools/perf/tests/shell/coresight_*
> > +F:	tools/perf/tests/shell/tools/Makefile
> > +F:	tools/perf/tests/shell/tools/coresight/*
> >  F:	tools/perf/util/cs-etm-decoder/*
> >  F:	tools/perf/util/cs-etm.*
> >  
> > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > index 80522bcfafe0..26467a2c71f4 100644
> > --- a/tools/perf/Makefile.perf
> > +++ b/tools/perf/Makefile.perf
> > @@ -630,7 +630,15 @@ sync_file_range_tbls := $(srctree)/tools/perf/trace/beauty/sync_file_range.sh
> >  $(sync_file_range_arrays): $(linux_uapi_dir)/fs.h $(sync_file_range_tbls)
> >  	$(Q)$(SHELL) '$(sync_file_range_tbls)' $(linux_uapi_dir) > $@
> >  
> > -all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS)
> > +TESTS_TOOLS_DIR := $(srctree)/tools/perf/tests/shell/tools
> > +
> > +tests-tools-targets: FORCE
> > +	$(Q)$(MAKE) -C $(TESTS_TOOLS_DIR)
> > +
> > +tests-tools-targets-clean:
> > +	$(Q)$(MAKE) -C $(TESTS_TOOLS_DIR) clean
> > +
> > +all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS) tests-tools-targets
> >  
> >  # Create python binding output directory if not already present
> >  _dummy := $(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
> > @@ -1020,6 +1028,7 @@ install-tests: all install-gtk
> >  		$(INSTALL) tests/shell/*.sh '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell'; \
> >  		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/lib'; \
> >  		$(INSTALL) tests/shell/lib/*.sh '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/lib'
> > +	$(Q)$(MAKE) -C tests/shell/tools install-tests
> >  
> >  install-bin: install-tools install-tests install-traceevent-plugins
> >  
> > @@ -1088,7 +1097,7 @@ endif # BUILD_BPF_SKEL
> >  bpf-skel-clean:
> >  	$(call QUIET_CLEAN, bpf-skel) $(RM) -r $(SKEL_TMP_OUT) $(SKELETONS)
> >  
> > -clean:: $(LIBTRACEEVENT)-clean $(LIBAPI)-clean $(LIBBPF)-clean $(LIBSUBCMD)-clean $(LIBPERF)-clean fixdep-clean python-clean bpf-skel-clean
> > +clean:: $(LIBTRACEEVENT)-clean $(LIBAPI)-clean $(LIBBPF)-clean $(LIBSUBCMD)-clean $(LIBPERF)-clean fixdep-clean python-clean bpf-skel-clean tests-tools-targets-clean
> >  	$(call QUIET_CLEAN, core-objs)  $(RM) $(LIBPERF_A) $(OUTPUT)perf-archive $(OUTPUT)perf-with-kcore $(OUTPUT)perf-iostat $(LANG_BINDINGS)
> >  	$(Q)find $(if $(OUTPUT),$(OUTPUT),.) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
> >  	$(Q)$(RM) $(OUTPUT).config-detected
> > @@ -1155,5 +1164,6 @@ FORCE:
> >  .PHONY: shell_compatibility_test please_set_SHELL_PATH_to_a_more_modern_shell
> >  .PHONY: $(GIT-HEAD-PHONY) TAGS tags cscope FORCE prepare
> >  .PHONY: libtraceevent_plugins archheaders
> > +.PHONY: $(TESTS_TOOLS_TARGETS)
> >  
> >  endif # force_fixdep
> > diff --git a/tools/perf/tests/shell/coresight_asm_pure_loop.sh b/tools/perf/tests/shell/coresight_asm_pure_loop.sh
> > new file mode 100755
> > index 000000000000..542d4a37e349
> > --- /dev/null
> > +++ b/tools/perf/tests/shell/coresight_asm_pure_loop.sh
> > @@ -0,0 +1,18 @@
> > +#!/bin/sh -e
> > +# Coresight / ASM Pure Loop
> > +
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Carsten Haitzler <carsten.haitzler@arm.com>, 2021
> > +
> > +TEST="asm_pure_loop"
> > +. $(dirname $0)/lib/coresight.sh
> > +ARGS=""
> > +DATV="out"
> > +DATA="$DATD/perf-$TEST-$DATV.data"
> > +
> > +perf record $PERFRECOPT -o "$DATA" "$BIN" $ARGS
> 
> Is $ARGS redundant and can be removed?
> 
> > +perf_dump_aux_verify "$DATA" 2601 334 334
> 
> These three magic numbers "2601 334 334" would be hard to understand.
> One way is the code can dynamically calculate these values based on the
> loop times (the loop is is predefined in asm_pure_loop.S), or it's
> good to give explanation in comments for these values.
> 
> > +
> > +err=$?
> > +exit $err
> > diff --git a/tools/perf/tests/shell/lib/coresight.sh b/tools/perf/tests/shell/lib/coresight.sh
> > new file mode 100644
> > index 000000000000..cd6c1283e6f5
> > --- /dev/null
> > +++ b/tools/perf/tests/shell/lib/coresight.sh
> > @@ -0,0 +1,130 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Carsten Haitzler <carsten.haitzler@arm.com>, 2021
> > +
> > +# This is sourced from a driver script so no need for #!/bin... etc. at the
> > +# top - the assumption below is that it runs as part of sourcing after the
> > +# test sets up some basic env vars to say what it is.
> > +
> > +# perf record options for the perf tests to use
> > +PERFRECMEM="-m ,128M"
> 
> We must use 128Mb for the AUX trace buffer?  The big buffer size is
> not friendly for embedded system.
> 
> > +PERFRECOPT="$PERFRECMEM -e cs_etm//u"
> > +
> > +# These tests need to be run as root or coresight won't allow large buffers
> > +# and will not collect proper data
> > +UID=`id -u`
> > +if test "$UID" -ne 0; then
> > +	echo "Not running as root... skip"
> > +	exit 2
> > +fi
> > +
> > +TOOLS=$(dirname $0)/tools
> > +DIR="$TOOLS/coresight/$TEST"
> > +BIN="$DIR/$TEST"
> > +# If the test tool/binary does not exist and is executable then skip the test
> > +if ! test -x "$BIN"; then exit 2; fi
> > +DATD="."
> 
> It's blur to set DATD and STATD to ".".  If the user doesn't specify
> the envs, it's not clear it will point to which folder.
> 
> > +# If the data dir env is set then make the data dir use that instead of ./
> > +if test -n "$PERF_TEST_CORESIGHT_DATADIR"; then
> > +	DATD="$PERF_TEST_CORESIGHT_DATADIR";
> > +fi
> > +# If the stat dir env is set then make the data dir use that instead of ./
> > +STATD="."
> > +if test -n "$PERF_TEST_CORESIGHT_STATDIR"; then
> > +	STATD="$PERF_TEST_CORESIGHT_STATDIR";
> > +fi
> > +
> > +# Called if the test fails - error code 2
> > +err() {
> > +	echo "$1"
> > +	exit 1
> > +}
> > +
> > +# Check that some statistics from our perf
> > +check_val_min() {
> > +	STATF="$4"
> > +	if test "$2" -lt "$3"; then
> > +		echo ", FAILED" >> "$STATF"
> > +		err "Sanity check number of $1 is too low ($2 < $3)"
> > +	fi
> > +}
> > +
> > +perf_dump_aux_verify() {
> > +	# Some basic checking that the AUX chunk contains some sensible data
> > +	# to see that we are recording something and at least a minimum
> > +	# amount of it. We should almost always see F3 atoms in just about
> > +	# anything but certainly we will see some trace info and async atom
> > +	# chunks.
> > +	DUMP="$DATD/perf-tmp-aux-dump.txt"
> > +	perf report --stdio --dump -i "$1" | \
> > +		grep -o -e I_ATOM_F3 -e I_ASYNC -e I_TRACE_INFO > "$DUMP"
> > +	# Simply count how many of these atoms we find to see that we are
> > +	# producing a reasonable amount of data - exact checks are not sane
> > +	# as this is a lossy  process where we may lose some blocks and the
> > +	# compiler may produce different code depending on the compiler and
> > +	# optimization options, so this is rough  just to see if we're
> > +	# either missing almost all the data or all of it
> > +	ATOM_F3_NUM=`grep I_ATOM_F3 "$DUMP" | wc -l`
> > +	ATOM_ASYNC_NUM=`grep I_ASYNC "$DUMP" | wc -l`
> > +	ATOM_TRACE_INFO_NUM=`grep I_TRACE_INFO "$DUMP" | wc -l`
> > +	rm -f "$DUMP"
> > +
> > +	# Arguments provide minimums for a pass
> > +	CHECK_F3_MIN="$2"
> > +	CHECK_ASYNC_MIN="$3"
> > +	CHECK_TRACE_INFO_MIN="$4"
> > +
> > +	# Write out statistics, so over time you can track results to see if
> > +	# there is a pattern - for example we have less "noisy" results that
> > +	# produce more consistent amounts of data each run, to see if over
> > +	# time any techinques to  minimize data loss are having an effect or
> > +	# not
> > +	STATF="$STATD/stats-$TEST-$DATV.csv"
> > +	if ! test -f "$STATF"; then
> > +		echo "ATOM F3 Count, Minimum, ATOM ASYNC Count, Minimum, TRACE INFO Count, Minimum" > "$STATF"
> > +	fi
> > +	echo -n "$ATOM_F3_NUM, $CHECK_F3_MIN, $ATOM_ASYNC_NUM, $CHECK_ASYNC_MIN, $ATOM_TRACE_INFO_NUM, $CHECK_TRACE_INFO_MIN" >> "$STATF"
> > +
> > +	# Actually check to see if we passed or failed.
> > +	check_val_min "ATOM_F3" "$ATOM_F3_NUM" "$CHECK_F3_MIN" "$STATF"
> > +	check_val_min "ASYNC" "$ATOM_ASYNC_NUM" "$CHECK_ASYNC_MIN" "$STATF"
> > +	check_val_min "TRACE_INFO" "$ATOM_TRACE_INFO_NUM" "$CHECK_TRACE_INFO_MIN" "$STATF"
> > +	echo ", Ok" >> "$STATF"
> > +}
> > +
> > +perf_dump_aux_tid_verify() {
> 
> This function is not used in the test contained in this patch.
> 
> > +	# Specifically crafted test will produce a list of Tread ID's to
> > +	# stdout that need to be checked to  see that they have had trace
> > +	# info collected in AUX blocks in the perf data. This will go
> > +	# through all the TID's that are listed as CID=0xabcdef and see
> > +	# that all the Thread IDs the test tool reports are  in the perf
> > +	# data AUX chunks
> > +
> > +	# The TID test tools will print a TID per stdout line that are being
> > +	# tested
> > +	TIDS=`cat "$2"`
> > +	# Scan the perf report to find the TIDs that are actually CID in hex
> > +	# and build a list of the ones found
> > +	FOUND_TIDS=`perf report --stdio --dump -i "$1" | \
> > +			grep -o "CID=0x[0-9a-z]\+" | sed 's/CID=//g' | \
> > +			uniq | sort | uniq`
> > +
> > +	# Iterate over the list of TIDs that the test says it has and find
> > +	# them in the TIDs found in the perf report
> > +	MISSING=""
> > +	for TID2 in $TIDS; do
> > +		FOUND=""
> > +		for TIDHEX in $FOUND_TIDS; do
> > +			TID=`printf "%i" $TIDHEX`
> > +			if test "$TID" -eq "$TID2"; then
> > +				FOUND="y"
> > +				break
> > +			fi
> > +		done
> > +		if test -z "$FOUND"; then
> > +			MISSING="$MISSING $TID"
> > +		fi
> > +	done
> > +	if test -n "$MISSING"; then
> > +		err "Thread IDs $MISSING not found in perf AUX data"
> > +	fi
> > +}
> > diff --git a/tools/perf/tests/shell/tools/Makefile b/tools/perf/tests/shell/tools/Makefile
> > new file mode 100644
> > index 000000000000..c7ada20922fd
> > --- /dev/null
> > +++ b/tools/perf/tests/shell/tools/Makefile
> > @@ -0,0 +1,26 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +# Carsten Haitzler <carsten.haitzler@arm.com>, 2021
> > +include ../../../../../tools/scripts/Makefile.include
> > +include ../../../../../tools/scripts/Makefile.arch
> > +include ../../../../../tools/scripts/utilities.mak
> 
> To be honest, I don't understand well for perf's build and config
> system.  Seems to me, a good example for building program is jevents.
> 
> Please take a look for the code:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Makefile.perf#n667
> 
> If follow the same method with jevents for building test programs,
> I can see one benefit is we don't need to create a Makefile, on the
> other hand, we can reuse the perf's build system and simply create a
> Build file under the folder tools/perf/tests/shell/.../coresight/.
> 
> > +
> > +SUBDIRS = \
> > +	coresight
> > +
> > +all: $(SUBDIRS)
> > +$(SUBDIRS):
> > +	$(Q)$(MAKE) -C $@
> > +
> > +INSTALLDIRS = $(SUBDIRS:%=install-%)
> > +
> > +install-tests: all $(INSTALLDIRS)
> > +$(INSTALLDIRS):
> > +	$(Q)$(MAKE) -C $(@:install-%=%) install-tests
> > +
> > +CLEANDIRS = $(SUBDIRS:%=clean-%)
> > +
> > +clean: $(CLEANDIRS)
> > +$(CLEANDIRS):
> > +	$(Q)$(MAKE) -C $(@:clean-%=%) O=$(OUTPUT) clean >/dev/null
> > +
> > +.PHONY: all clean install-tests $(SUBDIRS) $(CLEANDIRS) $(INSTALLDIRS)
> > diff --git a/tools/perf/tests/shell/tools/coresight/Makefile b/tools/perf/tests/shell/tools/coresight/Makefile
> > new file mode 100644
> > index 000000000000..723006ea827c
> > --- /dev/null
> > +++ b/tools/perf/tests/shell/tools/coresight/Makefile
> > @@ -0,0 +1,27 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +# Carsten Haitzler <carsten.haitzler@arm.com>, 2021
> > +include ../../../../../../tools/scripts/Makefile.include
> > +include ../../../../../../tools/scripts/Makefile.arch
> > +include ../../../../../../tools/scripts/utilities.mak
> > +
> > +SUBDIRS = \
> > +	asm_pure_loop
> > +
> > +all: $(SUBDIRS)
> > +$(SUBDIRS):
> > +	$(Q)$(MAKE) -C $@
> > +
> > +INSTALLDIRS = $(SUBDIRS:%=install-%)
> > +
> > +install-tests: $(INSTALLDIRS)
> > +$(INSTALLDIRS):
> > +	$(Q)$(MAKE) -C $(@:install-%=%) install-tests
> > +
> > +CLEANDIRS = $(SUBDIRS:%=clean-%)
> > +
> > +clean: $(CLEANDIRS)
> > +$(CLEANDIRS):
> > +	$(Q)$(MAKE) -C $(@:clean-%=%) clean >/dev/null
> > +
> > +.PHONY: all clean $(SUBDIRS) $(CLEANDIRS) $(INSTALLDIRS)
> > +
> > diff --git a/tools/perf/tests/shell/tools/coresight/Makefile.miniconfig b/tools/perf/tests/shell/tools/coresight/Makefile.miniconfig
> > new file mode 100644
> > index 000000000000..cedd26c6a0eb
> > --- /dev/null
> > +++ b/tools/perf/tests/shell/tools/coresight/Makefile.miniconfig
> > @@ -0,0 +1,23 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +# Carsten Haitzler <carsten.haitzler@arm.com>, 2021
> > +
> > +ifndef DESTDIR
> > +prefix ?= $(HOME)
> > +endif
> > +
> > +DESTDIR_SQ = $(subst ','\'',$(DESTDIR))
> > +perfexecdir = libexec/perf-core
> > +perfexec_instdir = $(perfexecdir)
> > +
> > +ifneq ($(filter /%,$(firstword $(perfexecdir))),)
> > +perfexec_instdir = $(perfexecdir)
> > +else
> > +perfexec_instdir = $(prefix)/$(perfexecdir)
> > +endif
> > +
> > +perfexec_instdir_SQ = $(subst ','\'',$(perfexec_instdir))
> > +INSTALL = install
> > +
> > +include ../../../../../../scripts/Makefile.include
> > +include ../../../../../../scripts/Makefile.arch
> > +include ../../../../../../scripts/utilities.mak
> 
> As suggested above, if we refer the building method of jevent, I think
> this Makefile.miniconfig is not needed anymore.
> 
> > diff --git a/tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile
> > new file mode 100644
> > index 000000000000..10c5a60cb71c
> > --- /dev/null
> > +++ b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/Makefile
> > @@ -0,0 +1,30 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Carsten Haitzler <carsten.haitzler@arm.com>, 2021
> > +
> > +include ../Makefile.miniconfig
> > +
> > +BIN=asm_pure_loop
> > +LIB=
> > +
> > +all: $(BIN)
> > +
> > +$(BIN): $(BIN).S
> > +ifdef CORESIGHT
> > +ifeq ($(ARCH),arm64)
> > +	$(Q)$(CC) $(BIN).S -nostdlib -static -o $(BIN) $(LIB)
> > +endif
> > +endif
> > +
> > +install-tests: all
> > +ifdef CORESIGHT
> > +ifeq ($(ARCH),arm64)
> > +	$(call QUIET_INSTALL, tests) \
> > +		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/tools/$(BIN)'; \
> > +		$(INSTALL) $(BIN) '$(DESTDIR_SQ)$(perfexec_instdir_SQ)/tests/shell/tools/$(BIN)/$(BIN)'
> > +endif
> > +endif
> > +
> > +clean:
> > +	$(Q)$(RM) -f $(BIN)
> > +
> > +.PHONY: all clean install-tests
> > diff --git a/tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S
> > new file mode 100644
> > index 000000000000..262876451021
> > --- /dev/null
> > +++ b/tools/perf/tests/shell/tools/coresight/asm_pure_loop/asm_pure_loop.S
> > @@ -0,0 +1,28 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/* Tamas Zsoldos <tamas.zsoldos@arm.com>, 2021 */
> > +
> > +.globl _start
> > +_start:
> > +	mov	x0, 0x000fffff
> > +	mov	x1, xzr
> > +loop:
> > +	nop
> > +	nop
> > +	cbnz	x1, noskip
> > +	nop
> > +	nop
> > +	adrp	x2, skip
> > +	add 	x2, x2, :lo12:skip
> > +	br	x2
> > +	nop
> > +	nop
> > +noskip:
> > +	nop
> > +	nop
> > +skip:
> > +	sub	x0, x0, 1
> > +	cbnz	x0, loop
> > +
> > +	mov	x0, #0
> > +	mov	x8, #93 // __NR_exit syscall
> > +	svc	#0
> 
> I verified this code on Arm64 machine and it works!
> 
> I am a bit worry about the code for using the hard code number for
> system call.  Another option is to use the inline assembly
> in C code, I think you have considered for this approach, this might
> introduce noise for extra branch instructions during the testing,
> but it can allow us to program standard C program (and don't worry
> about the program exiting).
> 
> If you think using assembly code is better than inline assembly, it
> would be fine for me.  Eventually, the system call number is very
> seldomly to be changed.
> 
> Thanks,
> Leo

-- 

- Arnaldo