glibc/manual
Zack Weinberg ea1bd74def New string function explicit_bzero (from OpenBSD).
explicit_bzero(s, n) is the same as memset(s, 0, n), except that the
compiler is not allowed to delete a call to explicit_bzero even if the
memory pointed to by 's' is dead after the call.  Right now, this effect
is achieved externally by having explicit_bzero be a function whose
semantics are unknown to the compiler, and internally, with a no-op
asm statement that clobbers memory.  This does mean that small
explicit_bzero operations cannot be expanded inline as small memset
operations can, but on the other hand, small memset operations do get
deleted by the compiler.  Hopefully full compiler support for
explicit_bzero will happen relatively soon.

There are two new tests: test-explicit_bzero.c verifies the
visible semantics in the same way as the existing test-bzero.c,
and tst-xbzero-opt.c verifies the not-being-optimized-out property.
The latter is conceptually based on a test written by Matthew Dempsky
for the OpenBSD regression suite.

The crypt() implementation has an immediate use for this new feature.
We avoid having to add a GLIBC_PRIVATE alias for explicit_bzero
by running all of libcrypt's calls through the fortified variant,
__explicit_bzero_chk, which is in the impl namespace anyway.  Currently
I'm not aware of anything in libc proper that needs this, but the
glue is all in place if it does become necessary.  The legacy DES
implementation wasn't bothering to clear its buffers, so I added that,
mostly for consistency's sake.

	* string/explicit_bzero.c: New routine.
	* string/test-explicit_bzero.c, string/tst-xbzero-opt.c: New tests.
	* string/Makefile (routines, strop-tests, tests): Add them.
	* string/test-memset.c: Add ifdeffage for testing explicit_bzero.
	* string/string.h [__USE_MISC]: Declare explicit_bzero.

	* debug/explicit_bzero_chk.c: New routine.
	* debug/Makefile (routines): Add it.
	* debug/tst-chk1.c: Test fortification of explicit_bzero.
	* string/bits/string3.h: Fortify explicit_bzero.

	* manual/string.texi: Document explicit_bzero.
	* NEWS: Mention addition of explicit_bzero.

	* crypt/crypt-entry.c (__crypt_r): Clear key-dependent intermediate
	data before returning, using explicit_bzero.
	* crypt/md5-crypt.c (__md5_crypt_r): Likewise.
	* crypt/sha256-crypt.c (__sha256_crypt_r): Likewise.
	* crypt/sha512-crypt.c (__sha512_crypt_r): Likewise.

	* include/string.h: Redirect internal uses of explicit_bzero
	to __explicit_bzero_chk[_internal].
	* string/Versions [GLIBC_2.25]: Add explicit_bzero.
	* debug/Versions [GLIBC_2.25]: Add __explicit_bzero_chk.
	* sysdeps/arm/nacl/libc.abilist
	* sysdeps/unix/sysv/linux/aarch64/libc.abilist
	* sysdeps/unix/sysv/linux/alpha/libc.abilist
	* sysdeps/unix/sysv/linux/arm/libc.abilist
	* sysdeps/unix/sysv/linux/hppa/libc.abilist
	* sysdeps/unix/sysv/linux/i386/libc.abilist
	* sysdeps/unix/sysv/linux/ia64/libc.abilist
	* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
	* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
	* sysdeps/unix/sysv/linux/microblaze/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
	* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
	* sysdeps/unix/sysv/linux/nios2/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist
	* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
	* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
	* sysdeps/unix/sysv/linux/sh/libc.abilist
	* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
	* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist
	* sysdeps/unix/sysv/linux/tile/tilepro/libc.abilist
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
	* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist:
	Add entries for explicit_bzero and __explicit_bzero_chk.
2016-12-16 16:21:54 -05:00
..
examples
argp.texi Manual typos: The Basic Program/System Interface 2016-10-06 12:19:25 +05:30
arith.texi Define FE_SNANS_ALWAYS_SIGNAL. 2016-12-16 18:03:25 +00:00
charset.texi
check-safety.sh
conf.texi Manual typos: System Configuration Parameters 2016-10-06 12:24:07 +05:30
contrib.texi Manual typos: Contributors to 2016-10-06 12:30:03 +05:30
creature.texi Make _REENTRANT and _THREAD_SAFE aliases for _POSIX_C_SOURCE=199506L. 2016-12-08 15:45:33 -05:00
crypt.texi Add getentropy, getrandom, <sys/random.h> [BZ #17252] 2016-12-12 17:28:04 +01:00
ctype.texi
debug.texi Manual typos: Debugging support 2016-10-06 12:25:38 +05:30
dir
errno.texi
fdl-1.3.texi
filesys.texi
freemanuals.texi
getopt.texi Manual typos: The Basic Program/System Interface 2016-10-06 12:19:25 +05:30
header.texi
install-plain.texi
install.texi Add pretty printers for the NPTL lock types 2016-12-08 18:59:02 +05:30
intro.texi
io.texi
ipc.texi
job.texi Manual typos: Job Control 2016-10-06 12:20:28 +05:30
lang.texi Manual typos: C Language Facilities in the Library 2016-10-06 12:27:48 +05:30
lgpl-2.1.texi
libc-texinfo.sh
libc.texinfo
libcbook.texi
libdl.texi
libm-err-tab.pl Add llogb, llogbf, llogbl. 2016-12-02 01:42:49 +00:00
llio.texi
locale.texi
macros.texi
maint.texi Manual typos: Library Maintenance 2016-10-06 12:29:11 +05:30
Makefile
math.texi Add getentropy, getrandom, <sys/random.h> [BZ #17252] 2016-12-12 17:28:04 +01:00
memory.texi Remove references to sbrk to grow/shrink arenas 2016-10-26 15:07:07 +05:30
message.texi
nss.texi Manual typos: System Databases and Name Service Switch 2016-10-06 12:36:26 +05:30
nsswitch.texi
pattern.texi
pipe.texi
platform.texi
probes.texi Manual typos: Internal probes 2016-10-06 12:26:35 +05:30
process.texi Manual typos: Processes 2016-10-06 12:20:00 +05:30
resource.texi Manual typos: Resource Usage and Limitation 2016-10-06 12:16:53 +05:30
search.texi
setjmp.texi Manual typos: Non-Local Exits 2016-10-06 12:17:29 +05:30
signal.texi Manual typos: Signal Handling 2016-10-06 12:18:05 +05:30
socket.texi
startup.texi Manual typos: The Basic Program/System Interface 2016-10-06 12:19:25 +05:30
stdio-fp.c
stdio.texi
string.texi New string function explicit_bzero (from OpenBSD). 2016-12-16 16:21:54 -05:00
summary.awk
sysinfo.texi manual: Remove non-existent mount options S_IMMUTABLE and S_APPEND [BZ #11235] 2016-11-15 15:56:00 -05:00
syslog.texi Manual typos: Syslog 2016-10-06 12:08:46 +05:30
terminal.texi Manual typos: Low-Level Terminal Interface 2016-10-06 12:07:28 +05:30
texinfo.tex
texis.awk
threads.texi Manual typos: POSIX Threads 2016-10-06 12:26:06 +05:30
time.texi Manual typos: Date and Time 2016-10-06 12:14:36 +05:30
tsort.awk
users.texi Manual typos: Users and Groups 2016-10-06 12:21:46 +05:30
xtract-typefun.awk