old-cross-binutils/gas
Maciej W. Rozycki 9d862524f6 MIPS: Verify the ISA mode and alignment of branch and jump targets
Verify that the ISA mode of branch targets is the same as the referring
relocation, so that an attempt to produce a branch between instructions
encoded in different ISA modes each causes an error rather than silently
producing non-functional code.  Make sure that no symbol or addend bits
are silently truncated: terminate with an error if the relocation value
calculated cannot be encoded in the relocatable field of a branch; for
REL targets also applying to any intermediate addend.

Also make jump target's alignment verification consistent with that for
branches.

This change will require an update to some obscure handcoded assembly
sources which make branches to labels placed at data objects, however
for microMIPS code only.  These labels will have to be updated with the
`.insn' directive for containing code to assemble and link successfully.
Such code is broken as any such labels have always been required by the
microMIPS architecture specification[1][2] to be annotated this way for
correct interpretation, and with our old code missing `.insn' directives
caused labels to present different semantics depending on whether they
were referred with branch (ISA bit ignored) or other relocations (ISA
bit respected).

Enforcing these checks however will ensure errors in building software,
like mixed regular MIPS and microMIPS code links with branches between,
will be diagnosed at the build time rather than causing odd run-time
errors such as intermittent crashes.  It will also let cross-mode BAL
instructions be converted to JALX instructions, with a separate change.

References:

[1] "MIPS Architecture for Programmers, Volume II-B: The microMIPS32
    Instruction Set", MIPS Technologies, Inc., Document Number: MD00582,
    Revision 5.04, January 15, 2014, Section 7.1 "Assembly-Level
    Compatibility", p. 533

[2] "MIPS Architecture for Programmers, Volume II-B: The microMIPS64
    Instruction Set", MIPS Technologies, Inc., Document Number: MD00594,
    Revision 5.04, January 15, 2014, Section 8.1 "Assembly-Level
    Compatibility", p. 623

	bfd/
	* elfxx-mips.c (b_reloc_p): Add R_MICROMIPS_PC16_S1,
	R_MICROMIPS_PC10_S1 and R_MICROMIPS_PC7_S1.
	(branch_reloc_p): New function.
	(mips_elf_calculate_relocation): Handle ISA mode determination
	for relocations against section symbols, against absolute
	symbols and absolute relocations.  Also set `*cross_mode_jump_p'
	for branches.
	<R_MIPS16_26, R_MIPS_26, R_MICROMIPS_26_S1>: Suppress alignment
	checks for weak undefined symbols.  Also check target alignment
	within the same ISA mode.
	<R_MIPS_PC16, R_MIPS_GNU_REL16_S2>: Handle cross-mode branches
	in the alignment check.
	<R_MICROMIPS_PC7_S1>: Add an alignment check.
	<R_MICROMIPS_PC10_S1>: Likewise.
	<R_MICROMIPS_PC16_S1>: Likewise.
	(mips_elf_perform_relocation): Report a failure for unsupported
	same-mode JALX instructions and cross-mode branches.
	(_bfd_mips_elf_relocate_section) <bfd_reloc_outofrange>: Add
	error messages for jumps to misaligned addresses.

	gas/
	* config/tc-mips.c (mips_force_relocation): Also retain branch
	relocations against MIPS16 and microMIPS symbols.
	(fix_bad_cross_mode_jump_p): New function.
	(fix_bad_same_mode_jalx_p): Likewise.
	(fix_bad_misaligned_jump_p): Likewise.
	(fix_bad_cross_mode_branch_p): Likewise.
	(fix_bad_misaligned_branch_p): Likewise.
	(fix_validate_branch): Likewise.
	(md_apply_fix) <BFD_RELOC_MIPS_JMP, BFD_RELOC_MIPS16_JMP>
	<BFD_RELOC_MICROMIPS_JMP>: Separate from BFD_RELOC_MIPS_SHIFT5,
	etc.  Verify the ISA mode and alignment of the jump target.
	<BFD_RELOC_MIPS_21_PCREL_S2>: Replace the inline alignment check
	with a call to `fix_validate_branch'.
	<BFD_RELOC_MIPS_26_PCREL_S2>: Likewise.
	<BFD_RELOC_16_PCREL_S2>: Likewise.
	<BFD_RELOC_MICROMIPS_7_PCREL_S1, BFD_RELOC_MICROMIPS_10_PCREL_S1>
	<BFD_RELOC_MICROMIPS_16_PCREL_S1>: Retain the original addend.
	Verify the ISA mode and alignment of the branch target.
	(md_convert_frag): Verify the ISA mode and alignment of resolved
	MIPS16 branch targets.
	* testsuite/gas/mips/branch-misc-1.s: Annotate non-instruction
	branch targets with `.insn'.
	* testsuite/gas/mips/branch-misc-5.s: Likewise.
	* testsuite/gas/mips/micromips@branch-misc-5-64.d: Update
	accordingly.
	* testsuite/gas/mips/micromips@branch-misc-5pic-64.d: Likewise.
	* testsuite/gas/mips/micromips-branch-relax.s: Annotate
	non-instruction branch target with `.insn'.
	* testsuite/gas/mips/micromips.s: Replace microMIPS JALX targets
	with external symbols.
	* testsuite/gas/mips/micromips-insn32.d: Update accordingly.
	* testsuite/gas/mips/micromips-noinsn32.d: Likewise.
	* testsuite/gas/mips/micromips-trap.d: Likewise.
	* testsuite/gas/mips/micromips.d: Likewise.
	* testsuite/gas/mips/mips16.s: Annotate non-instruction branch
	targets with `.insn'.
	* testsuite/gas/mips/mips16.d: Update accordingly.
	* testsuite/gas/mips/mips16-64.d: Likewise.
	* testsuite/gas/mips/mips16-dwarf2.s: Annotate non-instruction
	branch target with `.insn'.
	* testsuite/gas/mips/relax-swap3.s: Likewise.
	* testsuite/gas/mips/branch-local-2.l: New list test.
	* testsuite/gas/mips/branch-local-3.l: New list test.
	* testsuite/gas/mips/branch-local-n32-2.l: New list test.
	* testsuite/gas/mips/branch-local-n32-3.l: New list test.
	* testsuite/gas/mips/branch-local-n64-2.l: New list test.
	* testsuite/gas/mips/branch-local-n64-3.l: New list test.
	* testsuite/gas/mips/unaligned-jump-1.l: New list test.
	* testsuite/gas/mips/unaligned-jump-2.l: New list test.
	* testsuite/gas/mips/unaligned-jump-3.d: New test.
	* testsuite/gas/mips/unaligned-jump-mips16-1.l: New list test.
	* testsuite/gas/mips/unaligned-jump-mips16-2.l: New list test.
	* testsuite/gas/mips/unaligned-jump-mips16-3.d: New test.
	* testsuite/gas/mips/unaligned-jump-micromips-1.l: New list
	test.
	* testsuite/gas/mips/unaligned-jump-micromips-2.l: New list
	test.
	* testsuite/gas/mips/unaligned-jump-micromips-3.d: New test.
	* testsuite/gas/mips/unaligned-branch-1.l: New list test.
	* testsuite/gas/mips/unaligned-branch-2.l: New list test.
	* testsuite/gas/mips/unaligned-branch-3.d: New test.
	* testsuite/gas/mips/unaligned-branch-r6-1.l: New list test.
	* testsuite/gas/mips/unaligned-branch-r6-2.l: New list test.
	* testsuite/gas/mips/unaligned-branch-r6-3.l: New list test.
	* testsuite/gas/mips/unaligned-branch-r6-4.l: New list test.
	* testsuite/gas/mips/unaligned-branch-r6-5.d: New test.
	* testsuite/gas/mips/unaligned-branch-r6-6.d: New test.
	* testsuite/gas/mips/unaligned-branch-mips16-1.l: New list test.
	* testsuite/gas/mips/unaligned-branch-mips16-2.l: New list test.
	* testsuite/gas/mips/unaligned-branch-mips16-3.d: New test.
	* testsuite/gas/mips/unaligned-branch-micromips-1.l: New list
	test.
	* testsuite/gas/mips/unaligned-branch-micromips-2.l: New list
	test.
	* testsuite/gas/mips/unaligned-branch-micromips-3.d: New test.
	* testsuite/gas/mips/branch-local-2.s: New test source.
	* testsuite/gas/mips/branch-local-3.s: New test source.
	* testsuite/gas/mips/branch-local-n32-2.s: New test source.
	* testsuite/gas/mips/branch-local-n32-3.s: New test source.
	* testsuite/gas/mips/branch-local-n64-2.s: New test source.
	* testsuite/gas/mips/branch-local-n64-3.s: New test source.
	* testsuite/gas/mips/unaligned-jump-1.s: New test source.
	* testsuite/gas/mips/unaligned-jump-2.s: New test source.
	* testsuite/gas/mips/unaligned-jump-mips16-1.s: New test source.
	* testsuite/gas/mips/unaligned-jump-mips16-2.s: New test source.
	* testsuite/gas/mips/unaligned-jump-micromips-1.s: New test
	source.
	* testsuite/gas/mips/unaligned-jump-micromips-2.s: New test
	source.
	* testsuite/gas/mips/unaligned-branch-1.s: New test source.
	* testsuite/gas/mips/unaligned-branch-2.s: New test source.
	* testsuite/gas/mips/unaligned-branch-r6-1.s: New test source.
	* testsuite/gas/mips/unaligned-branch-r6-2.s: New test source.
	* testsuite/gas/mips/unaligned-branch-r6-3.s: New test source.
	* testsuite/gas/mips/unaligned-branch-r6-4.s: New test source.
	* testsuite/gas/mips/unaligned-branch-mips16-1.s: New test
	source.
	* testsuite/gas/mips/unaligned-branch-mips16-2.s: New test
	source.
	* testsuite/gas/mips/unaligned-branch-micromips-1.s: New test
	source.
	* testsuite/gas/mips/unaligned-branch-micromips-2.s: New test
	source.
	* testsuite/gas/mips/mips.exp: Run the new tests.

	ld/
	* testsuite/ld-mips-elf/unaligned-jalx-1.d: Update error message
	expected.
	* testsuite/ld-mips-elf/unaligned-jalx-addend-1.d: Likewise.
	* testsuite/ld-mips-elf/unaligned-jalx-addend-mips16-1.d:
	Likewise.
	* testsuite/ld-mips-elf/unaligned-jalx-addend-micromips-1.d:
	Likewise.
	* testsuite/ld-mips-elf/unaligned-jalx-mips16-1.d: Likewise.
	* testsuite/ld-mips-elf/unaligned-jalx-micromips-1.d: Likewise.
	* testsuite/ld-mips-elf/undefweak-overflow.s: Add jumps,
	microMIPS BAL and MIPS16 instructions.
	* testsuite/ld-mips-elf/undefweak-overflow.d: Update
	accordingly.
	* testsuite/ld-mips-elf/unaligned-branch-2.d: New test.
	* testsuite/ld-mips-elf/unaligned-branch-r6-1.d: New test.
	* testsuite/ld-mips-elf/unaligned-branch-r6-2.d: New test.
	* testsuite/ld-mips-elf/unaligned-branch-mips16.d: New test.
	* testsuite/ld-mips-elf/unaligned-branch-micromips.d: New test.
	* testsuite/ld-mips-elf/unaligned-jump-mips16.d: New test.
	* testsuite/ld-mips-elf/unaligned-jump-micromips.d: New test.
	* testsuite/ld-mips-elf/unaligned-jump.d: New test.
	* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.
2016-07-19 14:46:30 +01:00
..
config MIPS: Verify the ISA mode and alignment of branch and jump targets 2016-07-19 14:46:30 +01:00
doc Add command line option to stop the assembler from padding the end of sections to their alignment boundary. 2016-06-27 13:51:06 +01:00
po Copyright update for binutils 2016-01-01 23:00:01 +10:30
testsuite MIPS: Verify the ISA mode and alignment of branch and jump targets 2016-07-19 14:46:30 +01:00
.gitignore
acinclude.m4
aclocal.m4 Regenerate Makefile.in/aclocal.m4 automake 1.11.6 2016-04-15 16:20:55 -07:00
app.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
as.c Allow ARC target to be configured with --with-cpu=<cpu-name>. 2016-06-30 11:14:41 +01:00
as.h Add command line option to stop the assembler from padding the end of sections to their alignment boundary. 2016-06-27 13:51:06 +01:00
asintl.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
atof-generic.c Remove use of alloca. 2016-03-21 16:31:46 +00:00
bignum.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
bit_fix.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
cgen.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
cgen.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ChangeLog MIPS: Verify the ISA mode and alignment of branch and jump targets 2016-07-19 14:46:30 +01:00
ChangeLog-0001
ChangeLog-0203
ChangeLog-2004
ChangeLog-2005
ChangeLog-2006
ChangeLog-2007
ChangeLog-2008
ChangeLog-2009
ChangeLog-2010
ChangeLog-2011
ChangeLog-2012
ChangeLog-2013
ChangeLog-2014
ChangeLog-2015 binutils ChangeLog rotation 2016-01-01 22:59:17 +10:30
ChangeLog-9295
ChangeLog-9697
ChangeLog-9899
compress-debug.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
compress-debug.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
cond.c Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
config.in Allow ARC target to be configured with --with-cpu=<cpu-name>. 2016-06-30 11:14:41 +01:00
configure Allow ARC target to be configured with --with-cpu=<cpu-name>. 2016-06-30 11:14:41 +01:00
configure.ac Allow ARC target to be configured with --with-cpu=<cpu-name>. 2016-06-30 11:14:41 +01:00
configure.com Copyright update for binutils 2016-01-01 23:00:01 +10:30
configure.tgt Default to --enable-compressed-debug-sections=gas for Linux/x86 2016-06-29 09:32:34 -07:00
CONTRIBUTORS Copyright update for binutils 2016-01-01 23:00:01 +10:30
COPYING
debug.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
dep-in.sed
depend.c use XNEW and related macros more 2016-04-03 20:43:23 -04:00
dw2gencfi.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
dw2gencfi.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
dwarf2dbg.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
dwarf2dbg.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ecoff.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
ecoff.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ehopt.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
emul-target.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
emul.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
expr.c use xstrdup, xmemdup0 and concat more 2016-05-13 00:35:51 -04:00
expr.h Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
flonum-copy.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
flonum-konst.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
flonum-mult.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
flonum.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
frags.c Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
frags.h Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
gdbinit.in
hash.c use XNEW and related macros more 2016-04-03 20:43:23 -04:00
hash.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
input-file.c use XNEW and related macros more 2016-04-03 20:43:23 -04:00
input-file.h Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
input-scrub.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
itbl-lex-wrapper.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
itbl-lex.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
itbl-lex.l Copyright update for binutils 2016-01-01 23:00:01 +10:30
itbl-ops.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
itbl-ops.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
itbl-parse.y fixup another old style function definition 2016-06-05 23:49:03 -04:00
listing.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
listing.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
literal.c get rid of K&R style args 2016-03-31 01:04:00 -04:00
macro.c Fix potential buffer overflows with sprintf and very large integer values. 2016-07-01 12:35:01 +01:00
macro.h Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
MAINTAINERS Copyright update for binutils 2016-01-01 23:00:01 +10:30
Makefile.am Don't include libbfd.h outside of bfd, part 1 2016-07-16 13:25:11 +09:30
Makefile.in Don't include libbfd.h outside of bfd, part 1 2016-07-16 13:25:11 +09:30
makefile.vms Copyright update for binutils 2016-01-01 23:00:01 +10:30
messages.c GAS: Fix a typo in `as_bad' description 2016-04-09 13:22:54 +01:00
NEWS Add marker for 2.27 branch. 2016-07-01 10:58:29 +02:00
obj.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
output-file.c Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
output-file.h Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00
read.c PR19896, Segmentation fault on bad input 2016-04-02 17:31:36 +10:30
read.h Add const qualifiers at various places. 2016-03-07 15:16:28 +00:00
README Copyright update for binutils 2016-01-01 23:00:01 +10:30
remap.c use XNEW and related macros more 2016-04-03 20:43:23 -04:00
sb.c replace some raw xmalloc / xrealloc with the XNEW* macros 2016-03-22 19:06:39 -04:00
sb.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
stabs.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
stamp-h.in
struc-symbol.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
subsegs.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
subsegs.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
symbols.c use XNEW and related macros more 2016-05-13 00:35:51 -04:00
symbols.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
tc.h cleanup FLT_CHARS and EXP_CHARS 2016-04-03 19:50:02 -04:00
write.c PR gas/20312: Do not pad sections to alignment on failed assembly 2016-06-30 15:11:23 +01:00
write.h Add more const type qualifiers to GAS sources. 2016-02-22 14:11:27 +00:00

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		README for GAS

A number of things have changed since version 1 and the wonderful
world of gas looks very different.  There's still a lot of irrelevant
garbage lying around that will be cleaned up in time.  Documentation
is scarce, as are logs of the changes made since the last gas release.
My apologies, and I'll try to get something useful.

Unpacking and Installation - Summary
====================================

See ../binutils/README.

To build just the assembler, make the target all-gas.

Documentation
=============

The GAS release includes texinfo source for its manual, which can be processed
into `info' or `dvi' forms.

The DVI form is suitable for printing or displaying; the commands for doing
this vary from system to system.  On many systems, `lpr -d' will print a DVI
file.  On others, you may need to run a program such as `dvips' to convert the
DVI file into a form your system can print.

If you wish to build the DVI file, you will need to have TeX installed on your
system.  You can rebuild it by typing:

	cd gas/doc
	make as.dvi

The Info form is viewable with the GNU Emacs `info' subsystem, or the
stand-alone `info' program, available as part of the GNU Texinfo distribution.
To build the info files, you will need the `makeinfo' program.  Type:

	cd gas/doc
	make info

Specifying names for hosts and targets
======================================

   The specifications used for hosts and targets in the `configure'
script are based on a three-part naming scheme, but some short
predefined aliases are also supported.  The full naming scheme encodes
three pieces of information in the following pattern:

     ARCHITECTURE-VENDOR-OS

   For example, you can use the alias `sun4' as a HOST argument or in a
`--target=TARGET' option.  The equivalent full name is
`sparc-sun-sunos4'.

   The `configure' script accompanying GAS does not provide any query
facility to list all supported host and target names or aliases.
`configure' calls the Bourne shell script `config.sub' to map
abbreviations to full names; you can read the script, if you wish, or
you can use it to test your guesses on abbreviations--for example:

     % sh config.sub i386v
     i386-unknown-sysv
     % sh config.sub i786v
     Invalid configuration `i786v': machine `i786v' not recognized


`configure' options
===================

   Here is a summary of the `configure' options and arguments that are
most often useful for building GAS.  `configure' also has several other
options not listed here.

     configure [--help]
               [--prefix=DIR]
               [--srcdir=PATH]
               [--host=HOST]
               [--target=TARGET]
               [--with-OPTION]
               [--enable-OPTION]

You may introduce options with a single `-' rather than `--' if you
prefer; but you may abbreviate option names if you use `--'.

`--help'
     Print a summary of the options to `configure', and exit.

`-prefix=DIR'
     Configure the source to install programs and files under directory
     `DIR'.

`--srcdir=PATH'
     Look for the package's source code in directory DIR.  Usually
     `configure' can determine that directory automatically.

`--host=HOST'
     Configure GAS to run on the specified HOST.  Normally the
     configure script can figure this out automatically.

     There is no convenient way to generate a list of all available
     hosts.

`--target=TARGET'
     Configure GAS for cross-assembling programs for the specified
     TARGET.  Without this option, GAS is configured to assemble .o files
     that run on the same machine (HOST) as GAS itself.

     There is no convenient way to generate a list of all available
     targets.

`--enable-OPTION'
     These flags tell the program or library being configured to
     configure itself differently from the default for the specified
     host/target combination.  See below for a list of `--enable'
     options recognized in the gas distribution.

`configure' accepts other options, for compatibility with configuring
other GNU tools recursively; but these are the only options that affect
GAS or its supporting libraries.

The `--enable' options recognized by software in the gas distribution are:

`--enable-targets=...'
     This causes one or more specified configurations to be added to those for
     which BFD support is compiled.  Currently gas cannot use any format other
     than its compiled-in default, so this option is not very useful.

`--enable-bfd-assembler'
     This causes the assembler to use the new code being merged into it to use
     BFD data structures internally, and use BFD for writing object files.
     For most targets, this isn't supported yet.  For most targets where it has
     been done, it's already the default.  So generally you won't need to use
     this option.

Compiler Support Hacks
======================

On a few targets, the assembler has been modified to support a feature
that is potentially useful when assembling compiler output, but which
may confuse assembly language programmers.  If assembler encounters a
.word pseudo-op of the form symbol1-symbol2 (the difference of two
symbols), and the difference of those two symbols will not fit in 16
bits, the assembler will create a branch around a long jump to
symbol1, and insert this into the output directly before the next
label: The .word will (instead of containing garbage, or giving an
error message) contain (the address of the long jump)-symbol2.  This
allows the assembler to assemble jump tables that jump to locations
very far away into code that works properly.  If the next label is
more than 32K away from the .word, you lose (silently); RMS claims
this will never happen.  If the -K option is given, you will get a
warning message when this happens.


REPORTING BUGS IN GAS
=====================

Bugs in gas should be reported to:

   bug-binutils@gnu.org.

They may be cross-posted to gcc-bugs@gnu.org if they affect the use of
gas with gcc.  They should not be reported just to gcc-bugs, since not
all of the maintainers read that list.

See ../binutils/README for what we need in a bug report.

Copyright (C) 2012-2016 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.