[PATCH 2/2] PR ld/26288: Allow the use of `--just-symbols' with ET_EXEC input

Maciej W. Rozycki macro@wdc.com
Thu Jul 23 08:23:31 GMT 2020


Fix a regression from commit a87e1817a435 ("Have the linker fail if any 
attempt to link in an executable is made.") and do not reject ET_EXEC 
input supplied with the `--just-symbols' option.  Such use is legitimate 
as the file requested is not actually linked and only the symbols are 
extracted. Furthermore it is often the most useful application, as 
already observed in our documentation for the option, where it allows 
"to refer symbolically to absolute locations of memory defined in other 
programs."

Provide a set of tests for the use of ET_EXEC with `--just-symbols'.  
These are excluded however for SH/PE targets because they complain if a 
section's VMA is 0:

ld: zero vma section reloc detected: `.text' #0 f=32795
ld: zero vma section reloc detected: `.data' #1 f=291

and for x86_64/PE targets because they seem to hardwire the VMA:

 100000000 12000000 01000000 00000000 00000000  ................

	ld/
	PR ld/26288
	* ldelf.c (ldelf_after_open): Do not reject ET_EXEC input 
	supplied with `--just-symbols'.
	* testsuite/ld-misc/just-symbols.exp: New test script.
	* testsuite/ld-misc/just-symbols-1.dd: New test dump.
	* testsuite/ld-misc/just-symbols.ld: New test linker script.
	* testsuite/ld-misc/just-symbols-0.s: New test source.
	* testsuite/ld-misc/just-symbols-1.s: New test source.
---
Hi,

 Additionally the tests fail with a couple of targets, which appear to be 
genuine bugs in the handling of `--just-symbols', so I have let the 
failures through for the respective maintainers to investigate:

* arm-symbianelf:

Segmentation fault
FAIL: Object with --just-symbols test

* mipsel-ps2-elf:

./ld-new: tmpdir/just-symbols-1.o: linking 32-bit code with 64-bit code
./ld-new: failed to merge target specific data of file tmpdir/just-symbols-1.o
FAIL: Executable with --just-symbols test

* msp430-elf:

./ld-new: error: tmpdir/just-symbols-1.o uses MSP430X instructions but tmpdir/just-symbols-0 uses unknown
./ld-new: error: tmpdir/just-symbols-1.o uses the small code model whereas tmpdir/just-symbols-0 uses the unknown code model
./ld-new: error: tmpdir/just-symbols-1.o uses the small data model whereas tmpdir/just-symbols-0 uses the unknown data model
./ld-new: error: tmpdir/just-symbols-1.o uses the small code model but tmpdir/just-symbols-0 uses the unknown data model
./ld-new: failed to merge target specific data of file tmpdir/just-symbols-1.o
FAIL: Executable with --just-symbols test

* powerpc-beos, powerpc-ibm-aix5.2.0, rs6000-aix4.3.3, rs6000-aix5.1:

/mnt/mnt/sdb/binutils-test/binutils-test/powerpc-beos/ld/../binutils/objdump: section '.data' mentioned in a -j option, but not found in any input file

FAIL: Object with --just-symbols test

(naturally the section is there if `-h' is used with `objdump' rather than 
`-s').

  Maciej
---
 ld/ldelf.c                             |    3 +
 ld/testsuite/ld-misc/just-symbols-0.s  |    4 ++
 ld/testsuite/ld-misc/just-symbols-1.dd |    5 ++
 ld/testsuite/ld-misc/just-symbols-1.s  |    4 ++
 ld/testsuite/ld-misc/just-symbols.exp  |   57 +++++++++++++++++++++++++++++++++
 ld/testsuite/ld-misc/just-symbols.ld   |    7 ++++
 6 files changed, 79 insertions(+), 1 deletion(-)

binutils-ld-r-just-symbols-et-exec.diff
Index: binutils/ld/ldelf.c
===================================================================
--- binutils.orig/ld/ldelf.c
+++ binutils/ld/ldelf.c
@@ -1043,7 +1043,8 @@ ldelf_after_open (int use_libpath, int n
   /* Do not allow executable files to be used as inputs to the link.  */
   for (abfd = link_info.input_bfds; abfd; abfd = abfd->link.next)
     {
-      if (elf_tdata (abfd) != NULL
+      if (!bfd_input_just_syms (abfd)
+	  && elf_tdata (abfd) != NULL
 	  && elf_tdata (abfd)->elf_header != NULL
 	  /* FIXME: Maybe check for other non-supportable types as well ?  */
 	  && elf_tdata (abfd)->elf_header->e_type == ET_EXEC)
Index: binutils/ld/testsuite/ld-misc/just-symbols-0.s
===================================================================
--- /dev/null
+++ binutils/ld/testsuite/ld-misc/just-symbols-0.s
@@ -0,0 +1,4 @@
+	.data
+	.org	0x12
+	.globl	foo
+foo:
Index: binutils/ld/testsuite/ld-misc/just-symbols-1.dd
===================================================================
--- /dev/null
+++ binutils/ld/testsuite/ld-misc/just-symbols-1.dd
@@ -0,0 +1,5 @@
+.*: +file format .*
+
+Contents of section \.data:
+ [0-9a-f]+ (?:(:?12000000|00120000|00000012) 0{8}|0{8} 00000012) 0{8} 0{8} .*
+#pass
Index: binutils/ld/testsuite/ld-misc/just-symbols-1.s
===================================================================
--- /dev/null
+++ binutils/ld/testsuite/ld-misc/just-symbols-1.s
@@ -0,0 +1,4 @@
+	.data
+bar:
+	.dc.a	foo
+	.org	0x10
Index: binutils/ld/testsuite/ld-misc/just-symbols.exp
===================================================================
--- /dev/null
+++ binutils/ld/testsuite/ld-misc/just-symbols.exp
@@ -0,0 +1,57 @@
+# Expect script for ld --just-symbols tests.
+#   Copyright (C) 2020 Free Software Foundation, Inc.
+#
+# This file is part of the GNU Binutils.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+# MA 02110-1301, USA.
+#
+
+# SH/PE targets complain about zero VMA.
+# x86_64/PE targets hardcode VMA to 0x100000000.
+if { [istarget sh-*-pe] \
+     || [istarget x86_64-*-cygwin] \
+     || [istarget x86_64-*-mingw*] \
+     || [istarget x86_64-*-pe] \
+     || [istarget x86_64-*-pep] } {
+    return
+}
+
+run_ld_link_tests {
+    {"Object for --just-symbols test"
+     "-r -T just-symbols.ld" ""
+     ""
+     {just-symbols-0.s}
+     {}
+     "just-symbols-0.o"}
+    {"Executable for --just-symbols test"
+     "-e 0 -T just-symbols.ld" ""
+     ""
+     {just-symbols-0.s}
+     {}
+     "just-symbols-0"}
+    {"Object with --just-symbols test"
+     "-e 0 -T just-symbols.ld --just-symbols=tmpdir/just-symbols-0.o" ""
+     ""
+     {just-symbols-1.s}
+     {{objdump {-s -j .data} just-symbols-1.dd}}
+     "just-symbols-1obj"}
+    {"Executable with --just-symbols test"
+     "-e 0 -T just-symbols.ld --just-symbols=tmpdir/just-symbols-0" ""
+     ""
+     {just-symbols-1.s}
+     {{objdump {-s -j .data} just-symbols-1.dd}}
+     "just-symbols-1exe"}
+}
Index: binutils/ld/testsuite/ld-misc/just-symbols.ld
===================================================================
--- /dev/null
+++ binutils/ld/testsuite/ld-misc/just-symbols.ld
@@ -0,0 +1,7 @@
+SECTIONS
+{
+  .text : { *(.text) }
+  .data : { *(.data) }
+  .bss  : {  *(.bss) }
+  /DISCARD/ : { *(*) }
+}


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