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PR23611, objcopy is not removing executable relocatable sections

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BFD handles ELF relocation sections in an executable differently to
relocation sections in a relocatable object.  For a relocatable
object, BFD carries the relocations as data associated with the
section to which they apply; The relocation section doesn't appear as
a separate section.  For an executable, dynamic relocation sections do
appear as separate sections.  This means that objcopy needs to use
different strategies when dealing with relocations.

When --remove-relocations was added to objcopy with commit
d3e5f6c8f1, objcopy lost the ability to remove dynamic relocation
sections such as .rela.plt from executables using the option
"--remove-section=.rela.plt".  This patch reinstates that
functionality.

I thought it best to keep --remove-relocations as is, rather than
extending to handle dynamic relocations as per the patch in the PR,
because executables linked with --emit-relocs may have both dynamic
and non-dynamic relocations.  In that case --remove-relocataions=* is
useful to remove all the non-dynamic relocations.

	PR binutils/23611
	* objcopy.c (handle_remove_section_option): Consider .rela and
	.rel sections for stripping directly as well as attached to the
	associated section they relocate.
	* doc/binutils.texi (remove-relocations): Specify that this
	option removes non-dynamic relocation sections.
	* testsuite/binutils-all/objcopy.exp
	(objcopy_remove_relocations_from_executable): New test.
This commit is contained in:
Alan Modra 2018-09-10 11:57:08 +09:30
parent 78f8307c93
commit f9853190c8
4 changed files with 59 additions and 14 deletions
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11
binutils/ChangeLog
View file

@ -1,3 +1,14 @@
2018-09-10 Alan Modra <amodra@gmail.com>
PR binutils/23611
* objcopy.c (handle_remove_section_option): Consider .rela and
.rel sections for stripping directly as well as attached to the
associated section they relocate.
* doc/binutils.texi (remove-relocations): Specify that this
option removes non-dynamic relocation sections.
* testsuite/binutils-all/objcopy.exp
(objcopy_remove_relocations_from_executable): New test.
2018-09-03 Nick Clifton <nickc@redhat.com>
* po/ja.po: Updated Japanese translation.

13
binutils/doc/binutils.texi
View file

@ -1321,17 +1321,20 @@ will remove all sections matching the pattern '.text.*', but will not
remove the section '.text.foo'.
@item --remove-relocations=@var{sectionpattern}
Remove relocations from the output file for any section matching
@var{sectionpattern}. This option may be given more than once. Note
that using this option inappropriately may make the output file
unusable. Wildcard characters are accepted in @var{sectionpattern}.
Remove non-dynamic relocations from the output file for any section
matching @var{sectionpattern}. This option may be given more than
once. Note that using this option inappropriately may make the output
file unusable, and attempting to remove a dynamic relocation section
such as @samp{.rela.plt} from an executable or shared library with
@option{--remove-relocations=.plt} will not work. Wildcard characters
are accepted in @var{sectionpattern}.
For example:
@smallexample
--remove-relocations=.text.*
@end smallexample
will remove the relocations for all sections matching the patter
will remove the relocations for all sections matching the pattern
'.text.*'.
If the first character of @var{sectionpattern} is the exclamation

6
binutils/objcopy.c
View file

@ -3943,7 +3943,7 @@ discard_relocations (bfd *ibfd ATTRIBUTE_UNUSED, asection *isection)
/* Wrapper for dealing with --remove-section (-R) command line arguments.
A special case is detected here, if the user asks to remove a relocation
section (one starting with ".rela." or ".rel.") then this removal must
be done using a different technique. */
be done using a different technique in a relocatable object. */
static void
handle_remove_section_option (const char *section_pattern)
@ -3952,11 +3952,9 @@ handle_remove_section_option (const char *section_pattern)
handle_remove_relocations_option (section_pattern + 5);
else if (strncmp (section_pattern, ".rel.", 5) == 0)
handle_remove_relocations_option (section_pattern + 4);
else
{
find_section_list (section_pattern, TRUE, SECTION_CONTEXT_REMOVE);
sections_removed = TRUE;
}
}
/* Copy relocations in input section ISECTION of IBFD to an output

33
binutils/testsuite/binutils-all/objcopy.exp
View file

@ -1223,3 +1223,36 @@ proc objcopy_test_without_global_symbol { } {
setup_xfail aarch64*-*-* arm*-*-*
objcopy_test_without_global_symbol
# objcopy remove relocation from executable test
proc objcopy_remove_relocations_from_executable { } {
global OBJCOPY
global srcdir
global subdir
global READELF
set test "remove-section relocation sections"
if { [target_compile $srcdir/$subdir/testprog.c tmpdir/pr23611 executable debug] != "" } {
untested $test
return
}
if [is_remote host] {
set objfile [remote_download host tmpdir/pr23611]
} else {
set objfile tmpdir/pr23611
}
set out tmpdir/pr23611.out
set exec_output1 [binutils_run $OBJCOPY "-R .rela.plt -R .rela.dyn -R .rel.plt -R .rel.dyn $objfile $out"]
set exec_output2 [binutils_run $READELF "-S $out"]
if { [string match "*.rel.plt*" $exec_output2] || [string match "*.rela.plt*" $exec_output2] || [string match "*.rel.dyn*" $exec_output2] || [string match "*.rela.dyn*" $exec_output2] } {
fail $test
return
}
pass $test
}
objcopy_remove_relocations_from_executable