linux-kernel - Re: [RFC PATCH 32/77] dtc-parser: Introduce last_header

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260119151145.2f67139e@bootlin.com>
Date: Mon, 19 Jan 2026 15:11:45 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: David Gibson <david@...son.dropbear.id.au>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Ayush Singh <ayush@...gleboard.org>,
 Geert Uytterhoeven <geert@...ux-m68k.org>,
 devicetree-compiler@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree-spec@...r.kernel.org, Hui Pu
 <hui.pu@...ealthcare.com>, Ian Ray <ian.ray@...ealthcare.com>, Luca
 Ceresoli <luca.ceresoli@...tlin.com>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>
Subject: Re: [RFC PATCH 32/77] dtc-parser: Introduce last_header_flags

On Thu, 15 Jan 2026 17:31:24 +1100
David Gibson <david@...son.dropbear.id.au> wrote:

> On Mon, Jan 12, 2026 at 03:19:22PM +0100, Herve Codina wrote:
> > The parser needs to get header flags value in different places.
> > 
> > It relies on the fact that the rule used to parse the dts file is always
> >   headers memreserves devicetree
> > 
> > With that only rule to parse the file, it uses '$<flags>-1' construct to
> > get the flags value.
> > 
> > With the future introduction of import symbols parsing, this rule will
> > change and the parser couldn't rely anymore on '$<flags>-1' to get flags
> > value. Indeed, import symbols parsing will add a new optional symbol in
> > this rule leading to two possible rules (with and without the new
> > symbol) to parse the source file.
> > 
> > Introduce the last_header_flags variable to explicitly keep track of
> > flags while also being agnostic of the rule structure and use this new
> > variable instead of '$<flags>-1'.  
> 
> I'm not sure this approach is safe: I'm not sure bison guarantees that
> semantic rules will always be executed in the same order, so using
> global variables is risky.

if rules were not executed in the same order '$<flags>-1' construct would
not work.

The problem is not the order. I don't think the order will change. The
problem is related to the number of items on stack.

With import symbols, that the stack will be:
  header memreserved devicetree
or
  header memreserved importsyms devicetree

Using '$-1' will no more be possible. Indeed, '$-1' from the devicetree
rule will reference 'header' in one case and 'memreserved' in the other
case.

Without a global variable, I don't know how to reference 'header' (or flags
value) in all cases.

Any better ideas are welcome.

Best regards,
Hervé