Re: [PATCH v6 26/30 (mawk fix)] objtool: Add function to get the name of a CPU feature

[Alexandre Chartre]

On 11/25/25 19:34, David Laight wrote:
> On Tue, 25 Nov 2025 15:43:10 +0100
> Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> wrote:
>
> > On 11/25/25 14:29, David Laight wrote:
> > > On Mon, 24 Nov 2025 17:48:55 +0100
> > > Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> wrote:
> > >    
> > > > Add a function to get the name of a CPU feature. The function is
> > > > architecture dependent and currently only implemented for x86. The
> > > > feature names are automatically generated from the cpufeatures.h
> > > > include file.
> > > >
> > > > Signed-off-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
> > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > > > Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > > > Link: https://patch.msgid.link/20251121095340.464045-27-alexandre.chartre@xxxxxxxxxx
> > > > ---
> > > >    .../x86/tools/gen-cpu-feature-names-x86.awk   | 34 +++++++++++++++++++
> > > >    tools/objtool/.gitignore                      |  1 +
> > > >    tools/objtool/Makefile                        |  1 +
> > > >    tools/objtool/arch/loongarch/special.c        |  5 +++
> > > >    tools/objtool/arch/powerpc/special.c          |  5 +++
> > > >    tools/objtool/arch/x86/Build                  | 10 ++++++
> > > >    tools/objtool/arch/x86/special.c              | 10 ++++++
> > > >    tools/objtool/include/objtool/special.h       |  2 ++
> > > >    8 files changed, 68 insertions(+)
> > > >    create mode 100644 tools/arch/x86/tools/gen-cpu-feature-names-x86.awk
> > > >
> > > > diff --git a/tools/arch/x86/tools/gen-cpu-feature-names-x86.awk b/tools/arch/x86/tools/gen-cpu-feature-names-x86.awk
> > > > new file mode 100644
> > > > index 0000000000000..cc4c7a3e6c2e2
> > > > --- /dev/null
> > > > +++ b/tools/arch/x86/tools/gen-cpu-feature-names-x86.awk
> > > > @@ -0,0 +1,34 @@
> > > > +#!/bin/awk -f
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +#
> > > > +# Copyright (c) 2025, Oracle and/or its affiliates.
> > > > +#
> > > > +# Usage: awk -f gen-cpu-feature-names-x86.awk cpufeatures.h > cpu-feature-names.c
> > > > +#
> > > > +
> > > > +BEGIN {
> > > > +	print "/* cpu feature name array generated from cpufeatures.h */"
> > > > +	print "/* Do not change this code. */"
> > > > +	print
> > > > +	print "static const char *cpu_feature_names[(NCAPINTS+NBUGINTS)*32] = {"
> > >
> > > Since this code is #include'd into a .c file the line above (and the final })
> > > can be in that source file.
> > > You only need to generate the initialisers here.
> >
> > Sure, I can do that.
> >
> > >    
> > > > +
> > > > +	value_expr = "\\([0-9*+ ]+\\)"
> > > > +}
> > > > +
> > > > +/^#define X86_FEATURE_/ {
> > > > +	if (match($0, value_expr)) {
> > > > +		value = substr($0, RSTART + 1, RLENGTH - 2)
> > > > +		print "\t[" value "] = \"" $2 "\","
> > > > +	}
> > >
> > > Can't you just do:
> > > 	print "\t[" $2 "] = \"" $2 "\","
> >
> >
> > I presume you mean:  print "\t[" $3 "] = \"" $2 "\","
>
> No $2 and $2, so it generates:
> 	[X86_FEATURE_RRSBA_CTRL] = "X86_FEATURE_RRSBA_CTRL",
>
> All the #defines are defined - so you might as well use them.
> I suggested this sed command that has the same effect:
> 	sed -n -E '/^#define (X86_(FEATURE|BUG)_([^	 ]*)).*/s//	[\1] = "\1",/p'
> which can be put directly into the makefile.
>
> It isn't as though the pattern match for lines has to be very selective.
> It just needs to be 'good enough' for the current file.

Yes, right! I initially wanted to not have to include cpufeatures.h so I used
the X86_FEATURE_* values directly. Then I added X86_BUG_* which required NCAPINTS
and so cpufeatures.h.

So. of course, sed is good enough. I will simplify this.

Thanks,

alex.