Moving _etext to after all read-only sections

[Jason R Thorpe <thorpej at zembu dot com>]

Something else caused me to notice this, but it seems like a bug
in any case.

In Binutils 2.9 and also in Binutils-current, _etext is placed
after .text but before .rodata, etc.  This is fine for normal
applications (the read-only sections are gathered together in
a single, contiguous read-only section from the point of view
of a program loader).  But for e.g. an operating system kernel,
this is problematic.  The kernel, while bootstrapping VM, only
really has the _etext symbol to work with if it wants to map
the text and read-only data of the kernel as read-only.  The
end result is that const data ends up being writable.

A simple patch to the 2.9 elf.sc fixes this... but it looks
like it might be more complicated in Binutils-current (what
is WRITABLE_RODATA anyhow? -- also I'm not completely clear
on the CREATE_SHLIB-SDATA2 and CREATE_SHLIB-SBSS2 stuff).

Does anyone have any thoughts as to the wisdom of this change?
It occurred to me as the obvious one (over e.g. adding a new
_ereadonly symbol, or something) because of the comment near
the beginning of the template:

  /* Read-only sections, merged into text segment: */

Index: elf.sc
===================================================================
RCS file: /cvsroot/gnusrc/gnu/dist/ld/scripttempl/elf.sc,v
retrieving revision 1.3
diff -c -r1.3 elf.sc
*** elf.sc	1999/02/02 20:27:21	1.3
--- elf.sc	2001/01/19 23:03:57
***************
*** 112,123 ****
      ${RELOCATING+*(.gnu.linkonce.t*)}
      ${RELOCATING+${OTHER_TEXT_SECTIONS}}
    } =${NOP-0}
-   ${RELOCATING+_etext = .;}
-   ${RELOCATING+PROVIDE (etext = .);}
    .fini    ${RELOCATING-0} : { *(.fini)    } =${NOP-0}
    .rodata  ${RELOCATING-0} : { *(.rodata) ${RELOCATING+*(.gnu.linkonce.r*)} }
    .rodata1 ${RELOCATING-0} : { *(.rodata1) }
    ${RELOCATING+${OTHER_READONLY_SECTIONS}}
  
    /* Adjust the address for the data segment.  We want to adjust up to
       the same address within the page on the next page up.  */
--- 112,123 ----
      ${RELOCATING+*(.gnu.linkonce.t*)}
      ${RELOCATING+${OTHER_TEXT_SECTIONS}}
    } =${NOP-0}
    .fini    ${RELOCATING-0} : { *(.fini)    } =${NOP-0}
    .rodata  ${RELOCATING-0} : { *(.rodata) ${RELOCATING+*(.gnu.linkonce.r*)} }
    .rodata1 ${RELOCATING-0} : { *(.rodata1) }
    ${RELOCATING+${OTHER_READONLY_SECTIONS}}
+   ${RELOCATING+_etext = .;}
+   ${RELOCATING+PROVIDE (etext = .);}
  
    /* Adjust the address for the data segment.  We want to adjust up to
       the same address within the page on the next page up.  */

-- 
        -- Jason R. Thorpe <thorpej@zembu.com>