linux-hardening - Re: [PATCH v2 1/7] mangle: Introduce C typeinfo mangling API

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Message-ID: <202509041805.5C660B7B70@keescook>
Date: Thu, 4 Sep 2025 18:09:09 -0700
From: Kees Cook <kees@...nel.org>
To: Andrew Pinski <andrew.pinski@....qualcomm.com>
Cc: Qing Zhao <qing.zhao@...cle.com>, Andrew Pinski <pinskia@...il.com>,
	Richard Biener <rguenther@...e.de>,
	Joseph Myers <josmyers@...hat.com>, Jan Hubicka <hubicka@....cz>,
	Richard Earnshaw <richard.earnshaw@....com>,
	Richard Sandiford <richard.sandiford@....com>,
	Marcus Shawcroft <marcus.shawcroft@....com>,
	Kyrylo Tkachov <kyrylo.tkachov@....com>,
	Kito Cheng <kito.cheng@...il.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Andrew Waterman <andrew@...ive.com>,
	Jim Wilson <jim.wilson.gcc@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dan Li <ashimida.1990@...il.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Ramon de C Valle <rcvalle@...gle.com>,
	Joao Moreira <joao@...rdrivepizza.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Bill Wendling <morbo@...gle.com>, gcc-patches@....gnu.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 1/7] mangle: Introduce C typeinfo mangling API

On Thu, Sep 04, 2025 at 05:50:45PM -0700, Andrew Pinski wrote:
> On Thu, Sep 4, 2025 at 5:27 PM Kees Cook <kees@...nel.org> wrote:
> > +
> > +  /* Unknown builtin type - this should never happen in a well-formed C program.  */
> > +  debug_tree (type);
> > +  internal_error ("mangle: Unknown builtin type in function %qD - please report this as a bug",
> > +                  current_function_context);
> 
> This should NOT be internal_error but rather sorry.

Ah, heh. I switched to internal_error because you'd suggested it in
the last version. Maybe I misunderstood where I should be using sorry vs
internal_error.

> > +       if (!name && !TYPE_NAME (type))
> > +         {
> > +           static char anon_name[128];
> 
> I am not a fan of a static variable here. Why not just a stack variable?

Oh, whoops. I will fix that.

> > +         {
> > +           /* Always show diagnostic information for missing struct names.  */
> > +           debug_tree (type);
> > +           internal_error ("mangle: Missing case in struct name extraction - please report this as a bug");
> 
> Again sorry rather than internal_error.
> 
> I still think it would be better if the hashing and mangling be one
> step rather than 2 separate steps.
> Especially since this is only used for the hashing and will most
> likely only used there ever.

In this version the hashing happens immediately. No full string is built
unless the dumpfile is enabled.

-Kees

-- 
Kees Cook