[PATCH] PR ld/21529: Use a linker script to limit output with the test case (was: Re: PR21529, internal error in linker.c)

["Maciej W. Rozycki" <macro at imgtec dot com>]

Complement commit d9409498813c ("Add a testcase for PR ld/21529") and 
use a linker script to prevent an inter-segment gap arranged by the 
default linker script associated with some targets such as `rx-elf':

$ ld -e main -o tmpdir/dump-elf tmpdir/pr21529.o
$ readelf -l tmpdir/dump-elf
Elf file type is EXEC (Executable file)
Entry point 0x10000004
There are 2 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg 
Align
  LOAD           0x001000 0x10000000 0x10000000 0x00008 0x00008 R E 
0x1000
  LOAD           0x001ffc 0xbffffffc 0xbffffffc 0x00004 0x00004 RW  
0x1000

 Section to Segment mapping:
  Segment Sections...
   00     .text
   01     .stack
$ 

and converted to padding with the use of the binary BFD for output from 
producing unreasonably large files.

	ld/
	* testsuite/ld-unique/pr21529.ld: New test linker script.
	* testsuite/ld-unique/pr21529.d: Use it.
---
On Wed, 7 Jun 2017, Alan Modra wrote:

> > I checked in this to add a testcase.
> 
> Thanks, but various targets fail this testcase due to ld not
> supporting binary output.  With the following, we're left with:
> 
> avr-elf  +FAIL: ld-unique/pr21529
> iq2000-elf  +FAIL: ld-unique/pr21529
> mips64-linux  +FAIL: ld-unique/pr21529
> mipsel-linux-gnu  +FAIL: ld-unique/pr21529
> mipsisa32el-linux  +FAIL: ld-unique/pr21529
> mips-linux  +FAIL: ld-unique/pr21529
> mipstx39-elf  +FAIL: ld-unique/pr21529
> rx-elf  +FAIL: ld-unique/pr21529
> 
> The avr and mips fails are segfaults due to accessing ELF data
> structures that aren't present when linking to binary.  The iq2000 and
> rx fails are timeouts when dumping an enormous binary output.  All of
> the fails I see are real bugs so shouldn't be hidden by xfail.  I'm
> leaving it to the target maintainers to fix..

 At least the `rx-elf' failure is not a bug of any kind, but rather 
resource exhaustion and the dump requested eventually completes.  The raw 
binary produced corresponds to what would be:

Elf file type is EXEC (Executable file)
Entry point 0x10000004
There are 2 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x001000 0x10000000 0x10000000 0x00008 0x00008 R E 0x1000
  LOAD           0x001ffc 0xbffffffc 0xbffffffc 0x00004 0x00004 RW  0x1000

 Section to Segment mapping:
  Segment Sections...
   00     .text
   01     .stack

if linked with the ELF output format.  Of course what LD produces with the 
binary output format is a sparse file:

$ stat tmpdir/dump
  File: `tmpdir/dump'
  Size: 2952790016      Blocks: 16         IO Block: 65536  regular file
[...]
$ 

however a subsequent `objdump -a' from that file is not and takes several 
GiB of actual storage and also time to produce:

$ stat tmpdir/dump.out
  File: `tmpdir/dump.out'
  Size: 11811160129     Blocks: 23068680   IO Block: 65536  regular file
[...]
$ 

I think it is unreasonable and also unnecessary for this test case to have 
such a large file produced, so can we have a reasonable linker script 
involved, such as:

SECTIONS
{
  .text : { *(.text) }
  /DISCARD/ : { *(*) }
}

so that we do not trip on individual targets' peculiarities?

 No regressions in testing and `rx-elf' is now all-pass.  OK for trunk and 
2.29?

  Maciej

binutils-ld-test-pr21529-script.diff
---
 ld/testsuite/ld-unique/pr21529.d  |    2 +-
 ld/testsuite/ld-unique/pr21529.ld |    5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

Index: binutils/ld/testsuite/ld-unique/pr21529.d
===================================================================
--- binutils.orig/ld/testsuite/ld-unique/pr21529.d	2017-07-07 00:25:03.000000000 +0100
+++ binutils/ld/testsuite/ld-unique/pr21529.d	2017-07-13 14:27:05.629216883 +0100
@@ -1,4 +1,4 @@
-#ld: --oformat binary -e main
+#ld: --oformat binary -T pr21529.ld -e main
 #objdump: -s -b binary
 #xfail: aarch64*-*-* arm*-*-* hppa-*-* ia64-*-* nds32*-*-* score-*-*
 
Index: binutils/ld/testsuite/ld-unique/pr21529.ld
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-unique/pr21529.ld	2017-07-13 04:21:31.223687000 +0100
@@ -0,0 +1,5 @@
+SECTIONS
+{
+  .text : { *(.text) }
+  /DISCARD/ : { *(*) }
+}