Enhance dl-tunables.list to allow specifying a default value for a
tunable that it would be initialized to.
* scripts/gen-tunables.awk: Recognize 'default' keyword in
dl-tunables.list.
* README.tunables: Document it.
As of now we don't need tunables to be writable after they have been
set initially, so there is no point in having them writable. Put
tunable_list in .data.rel.ro so that it is set as read-only after
relocation. This also allows us to move some of the dl_* variables
that are tunables controlled into the tunables infrastructure instead
of having two copies.
In future if we ever need specific tunables to be writable at runtime,
we can split the tunable_list into two.
Regression tested on x86_64 to verify that tests continue to pass.
* scripts/gen-tunables.awk: Add attribute_relro to
tunable_list.
Since commit 8b9e9c3c0b, security_level replaces
is_secure. There were some old files need to be updated.
2017-03-23 Sunyeop Lee <sunyeop97@gmail.com>
* README.tunables: Updated descriptions.
* elf/dl-tunables.list: Fixed typo: SXID_NONE -> NONE.
* scripts/gen-tunables.awk: Updated the code related to the commit.
Florian Weimer pointed out that we have three different kinds of
environment variables (and hence tunables):
1. Variables that are removed for setxid processes
2. Variables that are ignored in setxid processes but is passed on to
child processes
3. Variables that are passed on to child processes all the time
Tunables currently only does (2) and (3) when it should be doing (1)
for MALLOC_CHECK_. This patch enhances the is_secure flag in tunables
to an enum value that can specify which of the above three categories
the tunable (and its envvar alias) belongs to.
The default is for tunables to be in (1). Hence, all of the malloc
tunables barring MALLOC_CHECK_ are explicitly specified to belong to
category (2). There were discussions around abolishing category (2)
completely but we can do that as a separate exercise in 2.26.
Tested on x86_64 to verify that there are no regressions.
[BZ #21073]
* elf/dl-tunable-types.h (tunable_seclevel_t): New enum.
* elf/dl-tunables.c (tunables_strdup): Remove.
(get_next_env): Also return the previous envp.
(parse_tunables): Erase tunables of category
TUNABLES_SECLEVEL_SXID_ERASE.
(maybe_enable_malloc_check): Make MALLOC_CHECK_
TUNABLE_SECLEVEL_NONE if /etc/setuid-debug is accessible.
(__tunables_init)[TUNABLES_FRONTEND ==
TUNABLES_FRONTEND_valstring]: Update GLIBC_TUNABLES envvar
after parsing.
[TUNABLES_FRONTEND != TUNABLES_FRONTEND_valstring]: Erase
tunable envvars of category TUNABLES_SECLEVEL_SXID_ERASE.
* elf/dl-tunables.h (struct _tunable): Change member is_secure
to security_level.
* elf/dl-tunables.list: Add security_level annotations for all
tunables.
* scripts/gen-tunables.awk: Recognize and generate enum values
for security_level.
* elf/tst-env-setuid.c: New test case.
* elf/tst-env-setuid-tunables: new test case.
* elf/Makefile (tests-static): Add them.
The tunables framework allows us to uniformly manage and expose global
variables inside glibc as switches to users. tunables/README has
instructions for glibc developers to add new tunables.
Tunables support can be enabled by passing the --enable-tunables
configure flag to the configure script. This patch only adds a
framework and does not pose any limitations on how tunable values are
read from the user. It also adds environment variables used in malloc
behaviour tweaking to the tunables framework as a PoC of the
compatibility interface.
* manual/install.texi: Add --enable-tunables option.
* INSTALL: Regenerate.
* README.tunables: New file.
* Makeconfig (CPPFLAGS): Define TOP_NAMESPACE.
(before-compile): Generate dl-tunable-list.h early.
* config.h.in: Add HAVE_TUNABLES.
* config.make.in: Add have-tunables.
* configure.ac: Add --enable-tunables option.
* configure: Regenerate.
* csu/init-first.c (__libc_init_first): Move
__libc_init_secure earlier...
* csu/init-first.c (LIBC_START_MAIN):... to here.
Include dl-tunables.h, libc-internal.h.
(LIBC_START_MAIN) [!SHARED]: Initialize tunables for static
binaries.
* elf/Makefile (dl-routines): Add dl-tunables.
* elf/Versions (ld): Add __tunable_set_val to GLIBC_PRIVATE
namespace.
* elf/dl-support (_dl_nondynamic_init): Unset MALLOC_CHECK_
only when !HAVE_TUNABLES.
* elf/rtld.c (process_envvars): Likewise.
* elf/dl-sysdep.c [HAVE_TUNABLES]: Include dl-tunables.h
(_dl_sysdep_start): Call __tunables_init.
* elf/dl-tunable-types.h: New file.
* elf/dl-tunables.c: New file.
* elf/dl-tunables.h: New file.
* elf/dl-tunables.list: New file.
* malloc/tst-malloc-usable-static.c: New test case.
* malloc/Makefile (tests-static): Add it.
* malloc/arena.c [HAVE_TUNABLES]: Include dl-tunables.h.
Define TUNABLE_NAMESPACE.
(DL_TUNABLE_CALLBACK (set_mallopt_check)): New function.
(DL_TUNABLE_CALLBACK_FNDECL): New macro. Use it to define
callback functions.
(ptmalloc_init): Set tunable values.
* scripts/gen-tunables.awk: New file.
* sysdeps/mach/hurd/dl-sysdep.c: Include dl-tunables.h.
(_dl_sysdep_start): Call __tunables_init.
