PATCH: Tweaks to ARM SymbianOS configuration

PATCH: Tweaks to ARM SymbianOS configuration

[Mark Mitchell]

This patch makes several changes for ARM SymbianOS:

1) Paul Brook accidentally changed the SymbianOS configuration to use
   RELA, but like other ARM targets, SymbianOS uses REL.

2) SymbianOS needs several magic symbols defined to mark the
   beginnings and ends of various segments.  There are GNU
   equivalents, but the SymbianOS runtime has to work with multiple
   toolchains, so we need to provide the same names they're using
   elsewhere.

3) SymbianOS wants .plt at the end of the text sgement; their kernel
   depends on this.

4) On SymbianOS, .init_array and friends can be read-only; there are
   no relocations actually applied at runtime, due to the SymbianOS
   DLL model.

OK to apply?

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com

2005-01-23  Mark Mitchell  <mark@codesourcery.com>

	* elf32-arm.c (elf_backend_default_use_rela_p): Define to zero for
	SymbianOS. 

005-01-23  Mark Mitchell  <mark@codesourcery.com>

	* emulparams/armsymbian.sh (OTHER_READONLY_SECTIONS): Define, so
	as to include .ARM.exidx$${Base,Limit}.
	* ld/scripttempl/armbpabi.sc: Move .plt to end of text segment.
	Define IMAGE$$ER_RO$${Base,Limit} and SHT$$INIT_ARRAY$${Base,Limit}.
	Put .init_array, .fini_array, etc. into the read-only data
	segment. 

Index: bfd/elf32-arm.c
===================================================================
RCS file: /cvs/src/src/bfd/elf32-arm.c,v
retrieving revision 1.16
diff -c -5 -p -r1.16 elf32-arm.c
*** bfd/elf32-arm.c	11 Jan 2005 09:32:46 -0000	1.16
--- bfd/elf32-arm.c	23 Jan 2005 18:54:32 -0000
*************** elf32_arm_symbian_modify_segment_map (bf
*** 5915,5924 ****
  #undef elf_backend_may_use_rel_p
  #define elf_backend_may_use_rel_p   1
  #undef elf_backend_may_use_rela_p
  #define elf_backend_may_use_rela_p  0
  #undef elf_backend_default_use_rela_p
! #define elf_backend_default_use_rela_p 1
  #undef elf_backend_rela_normal
  #define elf_backend_rela_normal     0
  
  #include "elf32-target.h"
--- 5915,5924 ----
  #undef elf_backend_may_use_rel_p
  #define elf_backend_may_use_rel_p   1
  #undef elf_backend_may_use_rela_p
  #define elf_backend_may_use_rela_p  0
  #undef elf_backend_default_use_rela_p
! #define elf_backend_default_use_rela_p 0
  #undef elf_backend_rela_normal
  #define elf_backend_rela_normal     0
  
  #include "elf32-target.h"
Index: ld/emulparams/armsymbian.sh
===================================================================
RCS file: /cvs/src/src/ld/emulparams/armsymbian.sh,v
retrieving revision 1.5
diff -c -5 -p -r1.5 armsymbian.sh
*** ld/emulparams/armsymbian.sh	26 Oct 2004 18:41:52 -0000	1.5
--- ld/emulparams/armsymbian.sh	23 Jan 2005 18:55:05 -0000
*************** LITTLE_OUTPUT_FORMAT="$OUTPUT_FORMAT"
*** 7,15 ****
--- 7,25 ----
  TARGET1_IS_REL=1
  TARGET2_TYPE=abs
  # On BPABI systems, program headers should not be mapped.
  EMBEDDED=yes
  
+ # As for armelf.sh, but add the SymbianOS-specific
+ # .ARM.exidx$${Base,Limit} symbols.
+ OTHER_READONLY_SECTIONS="
+   .ARM.extab ${RELOCATING-0} : { *(.ARM.extab${RELOCATING+* .gnu.linkonce.armextab.*}) }
+   ${RELOCATING+ .ARM.exidx\$\$Base = . ; }
+   ${RELOCATING+ __exidx_start = .; }
+   .ARM.exidx ${RELOCATING-0} : { *(.ARM.exidx${RELOCATING+* .gnu.linkonce.armexidx.*}) }
+   ${RELOCATING+ __exidx_end = .; }
+   ${RELOCATING+ .ARM.exidx\$\$Limit = . ; }"
+ 
  # This value should match ELF_MAXPAGESIZE in BFD.  Otherwise, elf.c
  # will not place read-write sections in a separate ELF segment from
  # the read-only sections.
  MAXPAGESIZE=0x8000
Index: ld/scripttempl/armbpabi.sc
===================================================================
RCS file: /cvs/src/src/ld/scripttempl/armbpabi.sc,v
retrieving revision 1.3
diff -c -5 -p -r1.3 armbpabi.sc
*** ld/scripttempl/armbpabi.sc	26 Oct 2004 18:41:52 -0000	1.3
--- ld/scripttempl/armbpabi.sc	23 Jan 2005 18:55:20 -0000
*************** ${RELOCATING- /* For some reason, the So
*** 135,145 ****
    bug.  But for now assigning the zero vmas works.  */}
  
  SECTIONS
  {
    /* Read-only sections, merged into text segment: */
!   ${CREATE_SHLIB-${CREATE_PIE-${RELOCATING+PROVIDE (__executable_start = ${TEXT_START_ADDR}); . = ${TEXT_BASE_ADDRESS};}}}
    ${CREATE_SHLIB+${RELOCATING+. = ${SHLIB_BASE_ADDRESS};}}
    ${CREATE_PIE+${RELOCATING+. = ${SHLIB_BASE_ADDRESS};}}
    ${INITIAL_READONLY_SECTIONS}
  
  EOF
--- 135,148 ----
    bug.  But for now assigning the zero vmas works.  */}
  
  SECTIONS
  {
    /* Read-only sections, merged into text segment: */
!   ${CREATE_SHLIB-${CREATE_PIE-${RELOCATING+PROVIDE (__executable_start = ${TEXT_START_ADDR});}}}
!   /* SymbianOS uses this symbol.  */
!   ${CREATE_SHLIB-${CREATE_PIE-${RELOCATING+PROVIDE (Image\$\$ER_RO\$\$Base = ${TEXT_START_ADDR});}}} 
!   ${CREATE_SHLIB-${CREATE_PIE-${RELOCATING+ . = ${TEXT_BASE_ADDRESS};}}}
    ${CREATE_SHLIB+${RELOCATING+. = ${SHLIB_BASE_ADDRESS};}}
    ${CREATE_PIE+${RELOCATING+. = ${SHLIB_BASE_ADDRESS};}}
    ${INITIAL_READONLY_SECTIONS}
  
  EOF
*************** cat <<EOF
*** 148,159 ****
    { 
      ${RELOCATING+${INIT_START}}
      KEEP (*(.init))
      ${RELOCATING+${INIT_END}}
    } =${NOP-0}
- 
-   ${DATA_PLT-${BSS_PLT-${PLT}}}
    .text         ${RELOCATING-0} :
    {
      ${RELOCATING+${TEXT_START_SYMBOLS}}
      *(.text .stub${RELOCATING+ .text.* .gnu.linkonce.t.*})
      KEEP (*(.text.*personality*))
--- 151,160 ----
*************** cat <<EOF
*** 165,199 ****
    {
      ${RELOCATING+${FINI_START}}
      KEEP (*(.fini))
      ${RELOCATING+${FINI_END}}
    } =${NOP-0}
    ${RELOCATING+PROVIDE (__etext = .);}
    ${RELOCATING+PROVIDE (_etext = .);}
    ${RELOCATING+PROVIDE (etext = .);}
    ${WRITABLE_RODATA-${RODATA}}
    .rodata1      ${RELOCATING-0} : { *(.rodata1) }
    ${CREATE_SHLIB-${SDATA2}}
    ${CREATE_SHLIB-${SBSS2}}
-   ${OTHER_READONLY_SECTIONS}
-   .eh_frame_hdr : { *(.eh_frame_hdr) }
-   .eh_frame     ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.eh_frame)) }
-   .gcc_except_table ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
- 
-   /* Adjust the address for the data segment.  We want to adjust up to
-      the same address within the page on the next page up.  */
-   ${CREATE_SHLIB-${CREATE_PIE-${RELOCATING+. = ${DATA_ADDR};}}}
-   ${CREATE_SHLIB+${RELOCATING+. = ${SHLIB_DATA_ADDR};}}
-   ${CREATE_PIE+${RELOCATING+. = ${SHLIB_DATA_ADDR};}}
- 
-   /* Exception handling  */
-   .eh_frame     ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.eh_frame)) }
-   .gcc_except_table ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
  
!   /* Thread Local Storage sections  */
!   .tdata	${RELOCATING-0} : { *(.tdata${RELOCATING+ .tdata.* .gnu.linkonce.td.*}) }
!   .tbss		${RELOCATING-0} : { *(.tbss${RELOCATING+ .tbss.* .gnu.linkonce.tb.*})${RELOCATING+ *(.tcommon)} }
  
    /* Ensure the __preinit_array_start label is properly aligned.  We
       could instead move the label definition inside the section, but
       the linker would then create the section even if it turns out to
       be empty, which isn't pretty.  */
--- 166,191 ----
    {
      ${RELOCATING+${FINI_START}}
      KEEP (*(.fini))
      ${RELOCATING+${FINI_END}}
    } =${NOP-0}
+   /* The SymbianOS kernel requires that the PLT go at the end of the
+      text section.  */
+   ${DATA_PLT-${BSS_PLT-${PLT}}}
    ${RELOCATING+PROVIDE (__etext = .);}
    ${RELOCATING+PROVIDE (_etext = .);}
    ${RELOCATING+PROVIDE (etext = .);}
+   /* SymbianOS uses this symbol.  */
+   ${RELOCATING+PROVIDE (Image\$\$ER_RO\$\$Limit = .);}
    ${WRITABLE_RODATA-${RODATA}}
    .rodata1      ${RELOCATING-0} : { *(.rodata1) }
    ${CREATE_SHLIB-${SDATA2}}
    ${CREATE_SHLIB-${SBSS2}}
  
!   /* On SymbianOS, put  .init_array and friends in the read-only
!      segment; there is no runtime relocation applied to these
!      arrays.  */
  
    /* Ensure the __preinit_array_start label is properly aligned.  We
       could instead move the label definition inside the section, but
       the linker would then create the section even if it turns out to
       be empty, which isn't pretty.  */
*************** cat <<EOF
*** 201,217 ****
--- 193,232 ----
    ${RELOCATING+${CREATE_SHLIB-PROVIDE (__preinit_array_start = .);}}
    .preinit_array   ${RELOCATING-0} : { *(.preinit_array) }
    ${RELOCATING+${CREATE_SHLIB-PROVIDE (__preinit_array_end = .);}}
  
    ${RELOCATING+${CREATE_SHLIB-PROVIDE (__init_array_start = .);}}
+   /* SymbianOS uses this symbol.  */
+   ${RELOCATING+${CREATE_SHLIB-PROVIDE (SHT\$\$INIT_ARRAY\$\$Base = .);}}
    .init_array   ${RELOCATING-0} : { *(.init_array) }
+   /* SymbianOS uses this symbol.  */
+   ${RELOCATING+${CREATE_SHLIB-PROVIDE (SHT\$\$INIT_ARRAY\$\$Limit = .);}}
    ${RELOCATING+${CREATE_SHLIB-PROVIDE (__init_array_end = .);}}
  
    ${RELOCATING+${CREATE_SHLIB-PROVIDE (__fini_array_start = .);}}
    .fini_array   ${RELOCATING-0} : { *(.fini_array) }
    ${RELOCATING+${CREATE_SHLIB-PROVIDE (__fini_array_end = .);}}
  
+   ${OTHER_READONLY_SECTIONS}
+   .eh_frame_hdr : { *(.eh_frame_hdr) }
+   .eh_frame     ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.eh_frame)) }
+   .gcc_except_table ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
+ 
+   /* Adjust the address for the data segment.  We want to adjust up to
+      the same address within the page on the next page up.  */
+   ${CREATE_SHLIB-${CREATE_PIE-${RELOCATING+. = ${DATA_ADDR};}}}
+   ${CREATE_SHLIB+${RELOCATING+. = ${SHLIB_DATA_ADDR};}}
+   ${CREATE_PIE+${RELOCATING+. = ${SHLIB_DATA_ADDR};}}
+ 
+   /* Exception handling  */
+   .eh_frame     ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.eh_frame)) }
+   .gcc_except_table ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
+ 
+   /* Thread Local Storage sections  */
+   .tdata	${RELOCATING-0} : { *(.tdata${RELOCATING+ .tdata.* .gnu.linkonce.td.*}) }
+   .tbss		${RELOCATING-0} : { *(.tbss${RELOCATING+ .tbss.* .gnu.linkonce.tb.*})${RELOCATING+ *(.tcommon)} }
+ 
    ${RELOCATING+${CTOR}}
    ${RELOCATING+${DTOR}}
    .jcr          ${RELOCATING-0} : { KEEP (*(.jcr)) }
  
    ${RELOCATING+${DATARELRO}}

Re: PATCH: Tweaks to ARM SymbianOS configuration

[Daniel Jacobowitz]

On Sun, Jan 23, 2005 at 11:09:07AM -0800, Mark Mitchell wrote:
> Index: ld/scripttempl/armbpabi.sc
> ===================================================================
> RCS file: /cvs/src/src/ld/scripttempl/armbpabi.sc,v
> retrieving revision 1.3
> diff -c -5 -p -r1.3 armbpabi.sc
> *** ld/scripttempl/armbpabi.sc	26 Oct 2004 18:41:52 -0000	1.3
> --- ld/scripttempl/armbpabi.sc	23 Jan 2005 18:55:20 -0000


...


> !   /* SymbianOS uses this symbol.  */

Should these changes by in a Symbian-specific file, or are they really
applicable to all BPABI targets?

-- 
Daniel Jacobowitz

Re: PATCH: Tweaks to ARM SymbianOS configuration

[Daniel Jacobowitz]

On Sun, Jan 23, 2005 at 11:27:32AM -0800, Mark Mitchell wrote:
> Daniel Jacobowitz wrote:
> 
> >>!   /* SymbianOS uses this symbol.  */
> >
> >
> >Should these changes by in a Symbian-specific file, or are they really
> >applicable to all BPABI targets?
> 
> I inentionally punted on that issue because Symbian has raised that 
> issue for discussion by the ARM ABI group.  The BPABI doesn't presently 
> specify these symbols, but Symbian is requesting that it should.  ARM's 
> toolchain generates these symbols, which is why SymbianOS depends on 
> them; it's very likely that other BPABI platforms (PalmOS) do, but I 
> have no direct evidence one way or the other.

OK, that makes sense.  What about the other changes, for instance, in
placement of .plt?

-- 
Daniel Jacobowitz

Re: PATCH: Tweaks to ARM SymbianOS configuration

[Mark Mitchell]

Daniel Jacobowitz wrote:

>>!   /* SymbianOS uses this symbol.  */
> 
> 
> Should these changes by in a Symbian-specific file, or are they really
> applicable to all BPABI targets?

I inentionally punted on that issue because Symbian has raised that 
issue for discussion by the ARM ABI group.  The BPABI doesn't presently 
specify these symbols, but Symbian is requesting that it should.  ARM's 
toolchain generates these symbols, which is why SymbianOS depends on 
them; it's very likely that other BPABI platforms (PalmOS) do, but I 
have no direct evidence one way or the other.

Also, there's a ton of stuff in that linker script that's just copied 
from generic GNU ELF, but really need not be there on BPABI platforms. 
I'm not sure exactly how to handle that; we could aggressively rip it 
out, but then we might rip out too much.  I can't quite decide whether 
it's better to be like the generic ELF configuration (so that it's easy 
to add things in both places) or better to be minimal (so that it's easy 
to understand the BPABI script).

-- 
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304

Re: PATCH: Tweaks to ARM SymbianOS configuration

[Mark Mitchell]

Daniel Jacobowitz wrote:
> On Sun, Jan 23, 2005 at 11:27:32AM -0800, Mark Mitchell wrote:
> 
>>Daniel Jacobowitz wrote:
>>
>>
>>>>!   /* SymbianOS uses this symbol.  */
>>>
>>>
>>>Should these changes by in a Symbian-specific file, or are they really
>>>applicable to all BPABI targets?
>>
>>I inentionally punted on that issue because Symbian has raised that 
>>issue for discussion by the ARM ABI group.  The BPABI doesn't presently 
>>specify these symbols, but Symbian is requesting that it should.  ARM's 
>>toolchain generates these symbols, which is why SymbianOS depends on 
>>them; it's very likely that other BPABI platforms (PalmOS) do, but I 
>>have no direct evidence one way or the other.
> 
> 
> OK, that makes sense.  What about the other changes, for instance, in
> placement of .plt?

I think that change is harmless on other platforms, and avoiding 
additional (already hairy) conditionalization seemed worthwhile.  I 
don't mind parameterizing either the symbols or the section order if 
people think that's important; it just seemed like undue complication to me.

-- 
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304

Re: PATCH: Tweaks to ARM SymbianOS configuration

[Daniel Jacobowitz]

On Sun, Jan 23, 2005 at 12:07:06PM -0800, Mark Mitchell wrote:
> Daniel Jacobowitz wrote:
> >On Sun, Jan 23, 2005 at 11:27:32AM -0800, Mark Mitchell wrote:
> >
> >>Daniel Jacobowitz wrote:
> >>
> >>
> >>>>!   /* SymbianOS uses this symbol.  */
> >>>
> >>>
> >>>Should these changes by in a Symbian-specific file, or are they really
> >>>applicable to all BPABI targets?
> >>
> >>I inentionally punted on that issue because Symbian has raised that 
> >>issue for discussion by the ARM ABI group.  The BPABI doesn't presently 
> >>specify these symbols, but Symbian is requesting that it should.  ARM's 
> >>toolchain generates these symbols, which is why SymbianOS depends on 
> >>them; it's very likely that other BPABI platforms (PalmOS) do, but I 
> >>have no direct evidence one way or the other.
> >
> >
> >OK, that makes sense.  What about the other changes, for instance, in
> >placement of .plt?
> 
> I think that change is harmless on other platforms, and avoiding 
> additional (already hairy) conditionalization seemed worthwhile.  I 
> don't mind parameterizing either the symbols or the section order if 
> people think that's important; it just seemed like undue complication to me.

Fine by me then.

-- 
Daniel Jacobowitz

Re: PATCH: Tweaks to ARM SymbianOS configuration

[Mark Mitchell]

Daniel Jacobowitz wrote:

>>I think that change is harmless on other platforms, and avoiding 
>>additional (already hairy) conditionalization seemed worthwhile.  I 
>>don't mind parameterizing either the symbols or the section order if 
>>people think that's important; it just seemed like undue complication to me.
> 
> 
> Fine by me then.

Cool.  Thanks for the review!

(Sadly, however, I don't think you're able to approve my patch...)

-- 
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304

Re: PATCH: Tweaks to ARM SymbianOS configuration

[Nick Clifton]

Hi Mark,

> 2005-01-23  Mark Mitchell  <mark@codesourcery.com>
> 
> 	* elf32-arm.c (elf_backend_default_use_rela_p): Define to zero for
> 	SymbianOS. 
> 
> 005-01-23  Mark Mitchell  <mark@codesourcery.com>
> 
> 	* emulparams/armsymbian.sh (OTHER_READONLY_SECTIONS): Define, so
> 	as to include .ARM.exidx$${Base,Limit}.
> 	* ld/scripttempl/armbpabi.sc: Move .plt to end of text segment.
> 	Define IMAGE$$ER_RO$${Base,Limit} and SHT$$INIT_ARRAY$${Base,Limit}.
> 	Put .init_array, .fini_array, etc. into the read-only data
> 	segment. 

Approved - please apply.

Cheers
   Nick