Re: Unreviewed patches

["H. J. Lu" <hjl at lucon dot org>]

On Tue, Jun 03, 2003 at 04:45:21PM +0200, Jakub Jelinek wrote:
> On Mon, Jun 02, 2003 at 09:12:44PM -0700, H. J. Lu wrote:
> > On Mon, Jun 02, 2003 at 05:58:05PM -0700, Richard Henderson wrote:
> > > On Mon, Jun 02, 2003 at 12:40:40PM -0400, Jakub Jelinek wrote:
> > > > http://sources.redhat.com/ml/binutils/2003-05/msg00741.html
> > > 
> > > Since I think I suggested PT_GNU_STACK in the first place,
> > > I'm a bit biased, but I like this solution.  It's the least
> > > amount of work for the kernel in execing a new application
> > > short of having a dedicated ET_FLAGS bit (which we don't).
> > > 
> > > The patch is ok.
> > > 
> > 
> > I like the proposal. But I don't like the implementation.
> > I'd like to see a generic note section for properties of
> > a relocatable file. I will make a detailed suggestion
> > tomorrow.
> 
> The other are the ET_REL-only sections used to set the default value.
> Here, I don't understand if you want to keep the merged section in the
> binary/libraries or not and why is a generic section with lots of flags
> better than specialized section (I think ld has about the same amount
> of work with both variants).
> 

That is my point. There is not much more extra work. But we use it
to describe other unique properties.

I am enclosing my proposal here.


H.J.
----
I propose an optional property note section, .note.GNU-property, for relocatable files to describe some unique properties which linker has to take into account when processing the input files. The contents of this note section are:

	.section        .note.GNU-property
	.align          2
	.long           .L1 - .L0
	.long           .L3 - .L2
	.long           1
.L0:
	.asciz         "Compiler Vendor"
.L1:
	.align          2
.L2:
	.long		    gFlag (Generic flag)
	.long		    psFlag (Processor specific flag)
.L3:

gFlag and psFlag can be extended in pairs. The current valid bit in gFlag is

#define NT_GNU_EXEC_STACK	(0x1 << 0)

When this bit is set, it indicates that the input relocatable file contains code which requires executable stack.

If a linker supports the optional property note section, it should follow the rules below when processing the relocatable input for generating relocatable file, executable or shared library:

1. Relocatable files without this note section are considered as the NT_GNU_EXEC_STACK bit is set and as needing executable stack.
2. If any input relocatable files have the NT_GNU_EXEC_STACK bit set, a PT_GNU_STACK segment header should be created with PF_R|PF_W|PF_X.
3. If none of input relocatable files have the NT_GNU_EXEC_STACK bit set, a PT_GNU_STACK segment header should be created with PF_R|PF_W.
4. If all input relocatable files don't have this section, no PT_GNU_STACK segment header should be created.
5. The note section should be preserved in the output relocatable file if any input relocatable files have the note section. The NT_GNU_EXEC_STACK should be set if it is set in any input relocatable files.
6. The note section should be removed from the output when generating executable or shared library.