Re: [PATCH 2/3] perf arm64: Generate system call table from asm/unistd.h

[Hendrik Brueckner <brueckner@linux.ibm.com>]

Hi Kim,

On Tue, Jul 03, 2018 at 12:32:28PM -0500, Kim Phillips wrote:
> This should speed up accessing new system calls introduced with the
> kernel rather than waiting for libaudit updates to include them.
> 
> Using the existing other arch scripts resulted in this error:
> 
> tools/perf/arch/arm64/entry/syscalls//mksyscalltbl: 25: printf: __NR3264_ftruncate: expected numeric value
> 
> because, unlike other arches, asm-generic's unistd.h does things like:
> 
>  #define __NR_ftruncate __NR3264_ftruncate
> 
> Turning the scripts printf's %d into a %s resulted in this in the
> generated syscalls.c file:
> 
>     static const char *syscalltbl_arm64[] = {
>             [__NR3264_ftruncate] = "ftruncate",
> 
> So we use the host C compiler to fold the macros, and print them out
> from within a temporary C program, in order to get the correct output:
> 
>     static const char *syscalltbl_arm64[] = {
>             [46] = "ftruncate",
> 
> Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Thomas Richter <tmricht@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Signed-off-by: Kim Phillips <kim.phillips@arm.com>
> ---
>  tools/perf/arch/arm64/Makefile                | 21 ++++++++
>  .../arch/arm64/entry/syscalls/mksyscalltbl    | 54 +++++++++++++++++++
>  2 files changed, 75 insertions(+)
>  create mode 100755 tools/perf/arch/arm64/entry/syscalls/mksyscalltbl
> 
> diff --git a/tools/perf/arch/arm64/Makefile b/tools/perf/arch/arm64/Makefile
> index 91de4860faad..85fdf4949db3 100644
> --- a/tools/perf/arch/arm64/Makefile
> +++ b/tools/perf/arch/arm64/Makefile
> @@ -4,3 +4,24 @@ PERF_HAVE_DWARF_REGS := 1
>  endif
>  PERF_HAVE_JITDUMP := 1
>  PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET := 1
> +
> +#
> +# Syscall table generation for perf
> +#
> +
> +out    := $(OUTPUT)arch/arm64/include/generated/asm
> +header := $(out)/syscalls.c
> +sysdef := $(srctree)/tools/arch/arm64/include/uapi/asm/unistd.h
> +sysprf := $(srctree)/tools/perf/arch/arm64/entry/syscalls/
> +systbl := $(sysprf)/mksyscalltbl
> +
> +# Create output directory if not already present
> +_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +
> +$(header): $(sysdef) $(systbl)
> +	$(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(sysdef) > $@
> +
> +clean::
> +	$(call QUIET_CLEAN, arm64) $(RM) $(header)
> +
> +archheaders: $(header)
> diff --git a/tools/perf/arch/arm64/entry/syscalls/mksyscalltbl b/tools/perf/arch/arm64/entry/syscalls/mksyscalltbl
> new file mode 100755
> index 000000000000..1148302b7194
> --- /dev/null
> +++ b/tools/perf/arch/arm64/entry/syscalls/mksyscalltbl
> @@ -0,0 +1,54 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Generate system call table for perf. Derived from
> +# powerpc script.
> +#
> +# Copyright IBM Corp. 2017
> +# Author(s):  Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
> +# Changed by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
> +# Changed by: Kim Phillips <kim.phillips@arm.com>
> +
> +gcc=$1
> +hostcc=$2
> +input=$3
> +
> +if ! test -r $input; then
> +	echo "Could not read input file" >&2
> +	exit 1
> +fi
> +
> +create_table_from_c()
> +{
> +	local last_sc

For the sake of completion, also add the "sc" and "nr" local variables.

> +
> +	create_table_base=`mktemp -u /tmp/create-table-XXX`

- The -u is considered to be unsafe. But from below, I think you require
  this for the .c/.x file.  Alternatively, you could create the file
  (and prefer using more X for the template) and append to it.  Or pipe
  the C code to the $hostcc command, e.g.,
	$hostcc -o $create_table_base -x c -
  which would require a single temp file that would be overwritten by gcc.

> +	echo "#include <stdio.h>" > ${create_table_base}.c
> +	echo "#include \"$input\"" >> ${create_table_base}.c
> +
> +	echo "int main(int argc, char *argv[])" >> ${create_table_base}.c
> +	echo "{" >> ${create_table_base}.c

As alternative to these echos, use

cat >> ${create_table_base}.c <<-EoHEADER
	#include <stdio.h>
	#include "$input"
	int main(int argc, char *argv[])
	{
EoHeader

which is at least for larger portions a bit more readable.

> +	while read sc nr; do
> +		echo "	printf(\"\\\t[%d] = \\\"$sc\\\",\\\n\", __NR_$sc);" >> ${create_table_base}.c
> +		last_sc=$sc
> +	done
> +	echo "	printf(\"#define SYSCALLTBL_ARM64_MAX_ID %d\\\n\", __NR_$last_sc);" >> ${create_table_base}.c
> +	echo "}" >> ${create_table_base}.c
> +
> +	$hostcc -o ${create_table_base}.x ${create_table_base}.c
> +	${create_table_base}.x
> +}
> +
> +create_table()
> +{
> +	echo "static const char *syscalltbl_arm64[] = {"
> +	create_table_from_c
> +	echo '};'
> +
> +	$RM -f ${create_table_base}.[cx]

The $RM is obtained from the (make) environment.  I would prefer using rm here
to be able to run as standalone.

> +}
> +
> +$gcc -E -dM -x c  $input	       \
> +	|sed -ne 's/^#define __NR_//p' \
> +	|sort -t' ' -k2 -nu	       \
> +	|create_table
> -- 
> 2.17.1
> 
Kind regards,
  Hendrik

-- 
Hendrik Brueckner
brueckner@linux.ibm.com           | IBM Deutschland Research & Development GmbH
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