[PATCH v2] elf: Don't set .note.GNU-stack type to SHT_NOTE

[Michael Matz]

Hello,

On Tue, 13 Jan 2026, Jan Beulich wrote:

> >>>>> in linker scripts. I really wonder why
> >>>>> no-one has cared to respond to the patch when it was still uncommitted ...

Because at least me came to this particular inbox only today, after 
vacation and suchlike :)

> > 1. The meaning of the SHT_NOTE section is determined by the contents of
> > the section, not by section names.
> 
> The meaning of .note.GNU-stack has been tied to its name, no matter what
> the section type (and it was never meant to have any contents).
> 
> > 2. The sh_flags field of the SHT_NOTE section has no impact on the meaning of
> > the section.
> 
> Generally not, but whichever type it has - .note.GNU-stack is special.
> 
> Also, what wording in the spec do you derive this from?
> 
> > 3. SHT_NOTE sections are mapped to the PT_NOTE segment.
> 
> Again, whichever type it has - .note.GNU-stack has been special.
> 
> > .note.GNU-stack section is none of the above.  From day one, .note.GNU-stack
> > has been a SHT_PROGBITS section.   It is simply wrong to set it to SHT_NOTE.
> 
> Well, to me it simply was wrong (from day one) to make it SHT_PROGBITS
> (or to name it the way it is named).

What was wrong from the beginning was its name.  But as you rightly point 
out, it is the name that gives it its semantics, so we can't change that 
anymore.

It's type cannot be SHT_NOTE, because as H.J. rightly points out sections 
of such type (irrespective of name) are to conform to a certain format of 
contents.  In particular it _must_ contain a header, which .note.GNU-stack 
doesn't.

So, when it was introduced, and as it never had contents, there would have 
been two correct section types: SHT_PROGBITS and SHT_NOBITS.  PROGBITS was 
chosen, there's doesn't seem to be any argument in to favor one over the 
other.

So, while I sympathize with the want to align the sections name pattern 
matching .note.* with its type, it simply cannot be done.  The name cannot 
be changed for compatibility, and the type cannot by SHT_NOTE for 
correctness.  The only way I see would be to completely phase out 
.note.GNU-stack and replace it by some other marker than a section.

> Furthermore, if we were to stick to SHT_PROGBITS (i.e. my change to be
> reverted), what would be your alternative proposal to address the
> linker script issue (which is what all of this started from)?

First match wins, hence .note.GNU-stack must be special cased before a 
.note.* catchall, if anything needs to be done at all.

> > Readelf should at least issue a warning for an empty SHT_NOTE which
> > indicates a user error.
> 
> I disagree; there's no "user error" there.

An empty SHT_NOTE section would be an error, if such was generated by a 
user it would indeed be a user error.  SHT_NOTE section must contain 12 
bytes at least: namesz, descsz and type, each 32bits.


Ciao,
Michael.