linux-kernel - Re: [tip: objtool/core] objtool: Function to get the name of a CPU feature

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Message-ID: <cf0ecf1e-6d7c-4d5e-8f8a-27446b801c94@oracle.com>
Date: Mon, 24 Nov 2025 17:43:04 +0100
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Borislav Petkov <bp@...en8.de>, Peter Zijlstra <peterz@...radead.org>
Cc: alexandre.chartre@...cle.com, linux-kernel@...r.kernel.org,
        linux-tip-commits@...r.kernel.org,
        Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org
Subject: Re: [tip: objtool/core] objtool: Function to get the name of a CPU
 feature


On 11/24/25 13:26, Borislav Petkov wrote:
> On Mon, Nov 24, 2025 at 12:59:42PM +0100, Peter Zijlstra wrote:
>> On Mon, Nov 24, 2025 at 10:44:01AM -0000, tip-bot2 for Alexandre Chartre wrote:
>>> The following commit has been merged into the objtool/core branch of tip:
>>>
>>> Commit-ID:     afff4e5820e9a0d609740a83c366f3f0335db342
>>> Gitweb:        https://git.kernel.org/tip/afff4e5820e9a0d609740a83c366f3f0335db342
>>> Author:        Alexandre Chartre <alexandre.chartre@...cle.com>
>>> AuthorDate:    Fri, 21 Nov 2025 10:53:36 +01:00
>>> Committer:     Peter Zijlstra <peterz@...radead.org>
>>> CommitterDate: Mon, 24 Nov 2025 11:35:06 +01:00
>>>
>>> objtool: Function to get the name of a CPU feature
> 
> Also, this commit name needs a verb.

Ok, then:

objtool: Add function to get the name of a CPU feature

>> Boris just reported that this doesn't work on mawk, since it uses a GNU
>> awk extension (3rd argument for match()).
>>
>> Could you please look at writing this in strict POSIX awk?
> 
> The fail is:
> 
> awk: ../arch/x86/tools/gen-cpu-feature-names-x86.awk: line 20: syntax error at or near ,
> awk: ../arch/x86/tools/gen-cpu-feature-names-x86.awk: line 23: syntax error at or near }
> awk: ../arch/x86/tools/gen-cpu-feature-names-x86.awk: line 26: syntax error at or near ,
> awk: ../arch/x86/tools/gen-cpu-feature-names-x86.awk: line 29: syntax error at or near }
> make[5]: *** [arch/x86/Build:21: /root/kernel/linux/tools/objtool/arch/x86/lib/cpu-feature-names.c] Error 2
> make[5]: *** Deleting file '/root/kernel/linux/tools/objtool/arch/x86/lib/cpu-feature-names.c'
> make[4]: *** [/root/kernel/linux/tools/build/Makefile.build:142: arch/x86] Error 2
> make[4]: *** Waiting for unfinished jobs....
> make[3]: *** [Makefile:104: /root/kernel/linux/tools/objtool/objtool-in.o] Error 2
> make[2]: *** [Makefile:73: objtool] Error 2
> make[1]: *** [/root/kernel/linux/Makefile:1449: tools/objtool] Error 2
> make: *** [Makefile:248: __sub-make] Error 2
> 
> ls -al /usr/bin/awk
> lrwxrwxrwx 1 root root 21 Feb 19  2021 /usr/bin/awk -> /etc/alternatives/awk
> ls -al /etc/alternatives/awk
> lrwxrwxrwx 1 root root 13 Feb 19  2021 /etc/alternatives/awk -> /usr/bin/mawk
>

Here is a fix. It works with gawk and mawk:

diff --git a/tools/arch/x86/tools/gen-cpu-feature-names-x86.awk b/tools/arch/x86/tools/gen-cpu-feature-names-x86.awk
index 1b1c1d84225c2..cc4c7a3e6c2e2 100644
--- a/tools/arch/x86/tools/gen-cpu-feature-names-x86.awk
+++ b/tools/arch/x86/tools/gen-cpu-feature-names-x86.awk
@@ -12,19 +12,20 @@ BEGIN {
         print
         print "static const char *cpu_feature_names[(NCAPINTS+NBUGINTS)*32] = {"
  
-       feature_expr = "(X86_FEATURE_[A-Z0-9_]+)\\s+\\(([0-9*+ ]+)\\)"
-       debug_expr = "(X86_BUG_[A-Z0-9_]+)\\s+X86_BUG\\(([0-9*+ ]+)\\)"
+       value_expr = "\\([0-9*+ ]+\\)"
  }
  
  /^#define X86_FEATURE_/ {
-       if (match($0, feature_expr, m)) {
-               print "\t[" m[2] "] = \"" m[1] "\","
+       if (match($0, value_expr)) {
+               value = substr($0, RSTART + 1, RLENGTH - 2)
+               print "\t[" value "] = \"" $2 "\","
         }
  }
  
  /^#define X86_BUG_/ {
-       if (match($0, debug_expr, m)) {
-               print "\t[NCAPINTS*32+(" m[2] ")] = \"" m[1] "\","
+       if (match($0, value_expr)) {
+               value = substr($0, RSTART + 1, RLENGTH - 2)
+               print "\t[NCAPINTS*32+(" value ")] = \"" $2 "\","
         }
  }
  
I am going to send the updated patch.

Rgds,

alex.