Age | Commit message (Collapse) | Author | Files | Lines |
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While it may be argued that nested functions make the resulting
code easier to read, or worse to read the following two bugs
make it difficult to debug:
Bug 8300 - no local symbol information within nested or nesting
procedures
https://sourceware.org/bugzilla/show_bug.cgi?id=8300
Bug 53927 - wrong value for DW_AT_static_link
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53927
Until these are fixed I've made check_match a full function.
After they are fixed we can resume arguing about the merits
of nested functions on readability and maintenance.
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This commit fixes a bug where the dynamic loader would crash
when loading audit libraries, via LD_AUDIT, where those libraries
used TLS. The dynamic loader was not considering that the audit
libraries would use TLS and failed to bump the TLS generation
counter leaving TLS usage inconsistent after loading the audit
libraries.
https://sourceware.org/ml/libc-alpha/2014-02/msg00569.html
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Fixes bug 15804
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This patch, an updated version of
<https://sourceware.org/ml/libc-alpha/2014-01/msg00194.html> now
proposed for inclusion in glibc, extends the generation of PASS and
FAIL status in .test-result files for individual tests to cover tests
with their own custom makefile rules. This is just adding
$(evaluate-test) calls to all such rules, since tests with multiple
commands were previously split into separate tests.
Note that the tests the makefiles expect to fail (posix/annexc and
conformtest) currently get FAIL listed in the .test-result file,
rather than XFAIL; a subsequent patch will introduce a better XFAIL
mechanism.
Tested x86_64.
* Makefile ($(objpfx)c++-types-check.out): Use $(evaluate-test).
($(objpfx)check-local-headers.out): Likewise.
($(objpfx)begin-end-check.out): Likewise.
* Makerules (check-abi-%.out): Likewise.
* catgets/Makefile ($(objpfx)test1.cat): Likewise.
($(objpfx)test2.cat): Likewise.
($(objpfx)de/libc.cat): Likewise.
($(objpfx)test-gencat.out): Likewise.
* conform/Makefile ($(objpfx)run-conformtest.out): Likewise.
* elf/Makefile ($(objpfx)order-cmp.out): Likewise.
($(objpfx)noload-mem): Likewise.
($(objpfx)tst-pathopt.out): Likewise.
($(objpfx)tst-rtld-load-self.out): Likewise.
($(objpfx)tst-array1-cmp.out): Likewise.
($(objpfx)tst-array1-static-cmp.out): Likewise.
($(objpfx)tst-array2-cmp.out): Likewise.
($(objpfx)tst-array3-cmp.out): Likewise.
($(objpfx)tst-array4-cmp.out): Likewise.
($(objpfx)tst-array5-cmp.out): Likewise.
($(objpfx)tst-array5-static-cmp.out): Likewise.
($(objpfx)check-textrel.out): Likewise.
($(objpfx)check-execstack.out): Likewise.
($(objpfx)check-localplt.out): Likewise.
($(objpfx)order2-cmp.out): Likewise.
($(objpfx)tst-leaks1-mem): Likewise.
($(objpfx)tst-leaks1-static-mem): Likewise.
($(objpfx)tst-initorder-cmp.out): Likewise.
($(objpfx)tst-initorder2-cmp.out): Likewise.
($(objpfx)tst-unused-dep.out): Likewise.
($(objpfx)tst-unused-dep-cmp.out): Likewise.
* grp/Makefile ($(objpfx)tst_fgetgrent.out): Likewise.
* iconv/Makefile (test-iconvconfig): Likewise.
* iconvdata/Makefile ($(objpfx)mtrace-tst-loading): Likewise.
($(objpfx)iconv-test.out): Likewise.
($(objpfx)tst-tables.out): Likewise.
* intl/Makefile ($(objpfx)mtrace-tst-gettext): Likewise.
($(objpfx)tst-gettext.out): Likewise.
($(objpfx)tst-translit.out): Likewise.
($(objpfx)tst-gettext2.out): Likewise.
($(objpfx)tst-gettext4.out): Likewise.
($(objpfx)tst-gettext6.out): Likewise.
* io/Makefile ($(objpfx)ftwtest.out): Likewise.
* libio/Makefile ($(objpfx)test-freopen.out): Likewise.
($(objpfx)tst-fopenloc-cmp.out): Likewise.
($(objpfx)tst-fopenloc-mem.out): Likewise.
* malloc/Makefile ($(objpfx)tst-mtrace.out): Likewise.
* misc/Makefile ($(objpfx)tst-error1-mem): Likewise.
* posix/Makefile ($(objpfx)globtest.out): Likewise.
($(objpfx)wordexp-tst.out): Likewise.
($(objpfx)annexc.out): Likewise.
($(objpfx)tst-fnmatch-mem): Likewise.
($(objpfx)bug-regex2-mem): Likewise.
($(objpfx)bug-regex14-mem): Likewise.
($(objpfx)bug-regex21-mem): Likewise.
($(objpfx)bug-regex31-mem): Likewise.
($(objpfx)tst-vfork3-mem): Likewise.
($(objpfx)tst-rxspencer-no-utf8-mem): Likewise.
($(objpfx)tst-pcre-mem): Likewise.
($(objpfx)tst-boost-mem): Likewise.
($(objpfx)tst-getconf.out): Likewise.
($(objpfx)bug-ga2-mem): Likewise.
($(objpfx)bug-glob2-mem): Likewise.
* resolv/Makefile ($(objpfx)mtrace-tst-leaks): Likewise.
($(objpfx)mtrace-tst-leaks2): Likewise.
* stdio-common/Makefile ($(objpfx)tst-unbputc.out): Likewise.
($(objpfx)tst-printf.out): Likewise.
($(objpfx)tst-setvbuf1.out): Likewise.
($(objpfx)tst-setvbuf1-cmp.out): Likewise.
* stdlib/Makefile ($(objpfx)isomac.out): Likewise.
($(objpfx)tst-fmtmsg.out): Likewise.
* string/Makefile ($(objpfx)tst-svc-cmp.out): Likewise.
* sysdeps/x86/Makefile ($(objpfx)tst-xmmymm.out): Likewise.
localedata:
* Makefile ($(objpfx)sort-test.out): Use $(evaluate-test).
($(objpfx)tst-fmon.out): Likewise.
($(objpfx)tst-numeric.out): Likewise.
($(objpfx)tst-locale.out): Likewise.
($(objpfx)tst-rpmatch.out): Likewise.
($(objpfx)tst-trans.out): Likewise.
($(objpfx)tst-mbswcs.out): Likewise.
($(objpfx)tst-ctype.out): Likewise.
($(objpfx)tst-wctype.out): Likewise.
($(objpfx)tst-langinfo.out): Likewise.
($(objpfx)mtrace-tst-leaks): Likewise.
nptl:
* Makefile ($(objpfx)tst-stack3-mem): Use $(evaluate-test).
($(objpfx)tst-tls6.out): Likewise.
($(objpfx)tst-cleanup0.out): Likewise.
($(objpfx)tst-cleanup0-cmp.out): Likewise.
($(objpfx)tst-cancel-wrappers.out): Likewise.
($(objpfx)tst-oddstacklimit.out): Likewise.
nptl_db:
* Makefile ($(objpfx)db-symbols.out): Use
$(evaluate-test).
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This patch splits makefile rules that generate a file then run cmp to
check the contents of that file into separate rules to generate and
compare the file. This simplifies making those tests generate PASS /
FAIL results, by removing the need to insert && between commands in
the test so that a $(evaluate-test) call is reached. It also avoids
the oddity of the .out file being an intermediate file rather than the
final result generated, as noted for some of these tests in
<https://sourceware.org/ml/libc-alpha/2012-10/msg00894.html>.
In many cases, the rule to run the program was no longer needed
because the default rules for running test programs on the host to
generate a .out file sufficed. (I'm not asserting the commands run
after this patch are *exactly* the same as before, simply that the
rules did nothing special that appeared deliberate or relevant to
anything about what the tests were testing. In cases where the rules
redirected stderr as well as stdout, I left the existing rule's
redirection in place to avoid changing what gets compared with the
expected results.)
It's clear there is a lot in common between the various -cmp.out rules
and it might be possible in future to refactor them into more generic
support for the case of comparing test output against a baseline.
(Some baselines are *.exp, some *.expect, some directly embedded in
the makefiles, and nptl/tst-cleanupx0.expect appears unused.)
Tested x86_64.
* elf/Makefile ($(objpfx)order.out): Remove rule.
[$(run-built-tests) = yes] (tests): Depend on
$(objpfx)order-cmp.out.
($(objpfx)order-cmp.out): New rule.
[$(run-built-tests) = yes] (tests): Depend on
$(objpfx)tst-array1-cmp.out, $(objpfx)tst-array1-static-cmp.out,
$(objpfx)tst-array2-cmp.out, $(objpfx)tst-array3-cmp.out,
$(objpfx)tst-array4-cmp.out, $(objpfx)tst-array5-cmp.out and
$(objpfx)tst-array5-static-cmp.out.
($(objpfx)tst-array1.out): Remove rule.
($(objpfx)tst-array1-cmp.out): New rule.
($(objpfx)tst-array1-static.out): Remove rule.
($(objpfx)tst-array1-static-cmp.out): New rule.
($(objpfx)tst-array2.out): Remove rule.
($(objpfx)tst-array2-cmp.out): New rule.
($(objpfx)tst-array3.out): Remove rule.
($(objpfx)tst-array3-cmp.out): New rule.
($(objpfx)tst-array4.out): Remove rule.
($(objpfx)tst-array4-cmp.out): New rule.
($(objpfx)tst-array5.out): Remove rule.
($(objpfx)tst-array5-cmp.out): New rule.
($(objpfx)tst-array5-static.out): Remove rule.
($(objpfx)tst-array5-static-cmp.out): New rule.
[$(run-built-tests) = yes] (tests): Depend on
$(objpfx)order2-cmp.out.
($(objpfx)order2.out): Remove rule.
($(objpfx)order2-cmp.out): New rule.
($(objpfx)tst-initorder.out): Remove rule.
[$(run-built-tests) = yes] (tests): Depend on
$(objpfx)tst-initorder-cmp.out.
($(objpfx)tst-initorder-cmp.out): New rule.
($(objpfx)tst-initorder2.out): Remove rule.
[$(run-built-tests) = yes] (tests): Depend on
$(objpfx)tst-initorder2-cmp.out.
($(objpfx)tst-initorder2-cmp.out): New rule.
[$(run-built-tests) = yes] (tests): Depend on
$(objpfx)tst-unused-dep-cmp.out.
($(objpfx)tst-unused-dep-cmp.out): Do not run cmp.
($(objpfx)tst-unused-dep-cmp.out): New rule.
* stdio-common/Makefile [$(run-built-tests) = yes] (tests): Depend
on $(objpfx)tst-setvbuf1-cmp.out.
($(objpfx)tst-setvbuf1.out): Do not run cmp.
($(objpfx)tst-setvbuf1-cmp.out): New rule.
* string/Makefile [$(run-built-tests) = yes] (tests): Depend
$(objpfx)tst-svc-cmp.out instead of $(objpfx)tst-svc.out.
($(objpfx)tst-svc.out): Remove rule.
($(objpfx)tst-svc-cmp.out): New rule.
nptl:
* Makefile ($(objpfx)tst-cleanup0.out): Do not run cmp.
[$(run-built-tests) = yes] (tests): Depend on
$(objpfx)tst-cleanup0-cmp.out.
($(objpfx)tst-cleanup0-cmp.out): New rule.
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If you rerun "make check" in a tree where some tests have already been
run, it will rerun ABI tests because those do not create an output
file.
This patch changes those tests to create .out files so they only get
rerun if the dependencies (on the ABI baselines and the generated
.symlist files) indicate they should be rerun.
Tested x86_64.
* Makerules (check-abi-%): Change target to
$(objpfx)check-abi-%.out.
(check-abi target): Update dependencies.
(check-abi-pattern variable): Redirect output of diff to $@.
(check-abi variable): Likewise.
* elf/Makefile (check-abi): Update dependencies.
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MIPS has its own version of dl-lookup.c to deal with differences
between undefined symbol semantics in the PIC and non-PIC ABIs. This
is often liable to get out of date with respect to the generic file
(for example, the recent __builtin_expect changes didn't cover ports,
and it's not obvious to anyone changing dl-lookup.c that there would
be architecture-specific versions).
This patch adds a macro that dl-machine.h can define that is used in
the appropriate place in dl-lookup.c, so that MIPS no longer needs its
own version of that file.
Tested for mips64 that the only changes to disassembly of installed
shared libraries appear to be ld.so changes attributable to different
line numbers and paths in assertions.
* elf/dl-lookup.c (ELF_MACHINE_SYM_NO_MATCH): Define if not
already defined.
(do_lookup_x): Use ELF_MACHINE_SYM_NO_MATCH.
* sysdeps/mips/dl-lookup.c: Remove.
* sysdeps/mips/dl-machine.h (ELF_MACHINE_SYM_NO_MATCH): New macro.
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This reverts commit 35e8f7ab94c910659de9d507aa0f3e1f8973d914.
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This reverts commit 1f33d36a8a9e78c81bed59b47f260723f56bb7e6.
Conflicts:
elf/dl-misc.c
Also reverts the follow commits that were bug fixes to new code introduced
in the above commit:
063b2acbce83549df82ab30f5af573f1b9c4bd19
b627fdd58554bc36bd344dc40a8787c4b7a9cc46
e81c64bba13d2d8b2a4e53254a82cc80f27c8497
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This reverts commit 7f507ee17aee720fa423fa38502bc3caa0dd03d7.
Conflicts:
ChangeLog
nptl/tst-tls7.c
nptl/tst-tls7mod.c
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Fixes to address issues from BZ #15022 resolution, as follows:
* TLS updates to csu/libc-tls.c -- we now have a proper main map, so
there's no longer a need to create a separate fake one to keep TLS
structures,
* random updates to elf/dl-close.c -- LM_ID_BASE is now a valid name
space ID for static executables as well, so assert that we don't
unload the main map. Similarly dl_nns isn't supposed to be 0 for
static executables anymore,
* actual BZ #16046 fix to elf/dl-iteratephdr.c -- the dl_iterate_phdr
special function for static executables isn't needed anymore, provided
that l_phdr and l_phnum members of the main map have been properly
initialized (done in _dl_non_dynamic_init in elf/dl-support.c now),
* ld.so.cache loader update to elf/dl-load.c --
GL(dl_ns)[LM_ID_BASE]._ns_loaded is now always initialized in static
executables so can become the fallback loader map to check for
DF_1_NODEFLIB, provided that the l_flags_1 member of the main map has
been properly initialized (done in elf/dl-support.c now); this also
ensures previous semantics elsewhere in elf/dl-load.c,
* matching updates to elf/dl-support.c -- to complement the two fixes
above.
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ChangeLog:
2014-01-03 Andrew Hunter <ahh@google.com>
* elf/dl-open.c (): New comment.
* elf/dl-reloc.c (_dl_try_allocate_static_tls): Use
atomic_compare_and_exchange_bool_acq
(_dl_allocate_static_tls): Block signals.
* elf/dl-tls.c (allocate_and_init): Return void.
(_dl_update_slotinfo): Block signals, use atomic update.
nptl/ChangeLog:
2014-01-03 Andrew Hunter <ahh@google.com>
* nptl/Makefile (tst-tls7): New test.
* nptl/tst-tls7.c: New file.
* nptl/tst-tls7mod.c: New file.
* nptl/allocatestack.c (init_one_static_tls): Use atomic barrier.
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Update copyright years that are not handled by scripts/update-copyright.
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2013-12-19 Paul Pluzhnikov <ppluzhnikov@google.com>
* elf/dl-misc.c (ptr_to_signal_safe_allocator_header): New function.
(__signal_safe_memalign, __signal_safe_free): Use it.
(__signal_safe_realloc): Likewise.
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Add a signal-safe malloc replacement.
2013-12-18 Andrew Hunter <ahh@google.com>
* sysdeps/generic/ldsodefs.h (__signal_safe_memalign): New prototype.
(__signal_safe_malloc, __signal_safe_free): Likewise.
(__signal_safe_realloc, __signal_safe_calloc): Likewise.
* elf/dl-misc.c (__signal_safe_allocator_header): New struct.
(__signal_safe_memalign, __signal_safe_malloc): New function.
(__signal_safe_free, __signal_safe_realloc): Likewise.
(__signal_safe_calloc): Likewise.
* elf/dl-tls.c (allocate_dtv, _dl_clear_dtv): Call signal-safe
functions.
(_dl_deallocate_tls, _dl_update_slotinfo): Likewise.
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Factor out _dl_clear_dtv.
2013-12-18 Andrew Hunter <ahh@google.com>
* elf/Versions (ld): Add _dl_clear_dtv.
* sysdeps/generic/ldsodefs.h (_dl_clear_dtv): New prototype.
* elf/dl-tls.c (_dl_clear_dtv): New function.
* nptl/allocatestack.c (get_cached_stack): Call _dl_clear_dtv.
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[BZ 15846] As discussed in the recent thread on my $EXEC_ORIGIN patch
and in BZ 15846, getauxval() presently has no unambiguous way of
reporting an error condition. It currently returns zero on error, but
this may also be a valid result for some auxv entries. As there is no
clear invalid result for all current and future auxv entries, this patch
sets errno (following a suggestion in the BZ entry).
This version of the patch also adds documentation and tests for the
value-not-found conditions in getauxval().
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This is a follow-on to the previous patch to support the ELFv2 ABI in the
dynamic loader, split off into its own patch since it is just an optional
optimization.
In the ELFv2 ABI, most functions define both a global and a local entry
point; the local entry requires r2 to be already set up by the caller
to point to the callee's TOC; while the global entry does not require
the caller to know about the callee's TOC, but it needs to set up r12
to the callee's entry point address.
Now, when setting up a PLT slot, the dynamic linker will usually need
to enter the target function's global entry point. However, if the
linker can prove that the target function is in the same DSO as the
PLT slot itself, and the whole DSO only uses a single TOC (which the
linker will let ld.so know via a DT_PPC64_OPT entry), then it is
possible to actually enter the local entry point address into the
PLT slot, for a slight improvement in performance.
Note that this uncovered a problem on the first call via _dl_runtime_resolve,
because that routine neglected to restore the caller's TOC before calling
the target function for the first time, since it assumed that function
would always reload its own TOC anyway ...
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This patch adds support for the ELFv2 ABI feature to remove function
descriptors. See this GCC patch for in-depth discussion:
http://gcc.gnu.org/ml/gcc-patches/2013-11/msg01141.html
This mostly involves two types of changes: updating assembler source
files to the new logic, and updating the dynamic loader.
After the refactoring in the previous patch, most of the assembler source
changes can be handled simply by providing ELFv2 versions of the
macros in sysdep.h. One somewhat non-obvious change is in __GI__setjmp:
this used to "fall through" to the immediately following __setjmp ENTRY
point. This is no longer safe in the ELFv2 since ENTRY defines both
a global and a local entry point, and you cannot simply fall through
to a global entry point as it requires r12 to be set up.
Also, makecontext needs to be updated to set up registers according to
the new ABI for calling into the context's start routine.
The dynamic linker changes mostly consist of removing special code
to handle function descriptors. We also need to support the new PLT
and glink format used by the the ELFv2 linker, see:
https://sourceware.org/ml/binutils/2013-10/msg00376.html
In addition, the dynamic linker now verifies that the dynamic libraries
it loads match its own ABI.
The hack in VDSO_IFUNC_RET to "synthesize" a function descriptor
for vDSO routines is also no longer necessary for ELFv2.
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This patch updates glibc in accordance with the binutils patch checked in here:
https://sourceware.org/ml/binutils/2013-10/msg00372.html
This changes the various R_PPC64_..._HI and _HA relocations to report
32-bit overflows. The motivation is that existing uses of @h / @ha
are to build up 32-bit offsets (for the "medium model" TOC access
that GCC now defaults to), and we'd really like to see failures at
link / load time rather than silent truncations.
For those rare cases where a modifier is needed to build up a 64-bit
constant, new relocations _HIGH / _HIGHA are supported.
The patch also fixes a bug in overflow checking for the R_PPC64_ADDR30
and R_PPC64_ADDR32 relocations.
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On hppa and ia64, the macro DL_AUTO_FUNCTION_ADDRESS() uses the
variable fptr[2] in it's own scope.
The content of fptr[] is thus undefined right after the macro exits.
Newer gcc's (>= 4.7) reuse the stack space of this variable triggering
a segmentation fault in dl-init.c:69.
To fix this we rewrite the macros to make the call directly to init
and fini without needing to pass back a constructed function pointer.
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2013-11-18 Paul Pluzhnikov <ppluzhnikov@google.com>
* elf/Makefile (tst-auxv): New test.
* elf/tst-auxv.c: New
* elf/rtld.c (dl_main): Adjust AT_EXECFN
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2013-11-18 Paul Pluzhnikov <ppluzhnikov@google.com>
* elf/Makefile (tst-auxv): New test.
* elf/tst-auxv.c: New
* elf/rtld.c (dl_main): Adjust AT_EXECFN
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We first expanded origin and then split string by colons. This
misbehaves when $ORIGIN contain colon so we first split string, then
expand $ORIGIN.
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Remove tls.h includes where they are not needed.
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It was noted in 2005 (BZ #832), 2006 (BZ #3266), and 2007 [1] that ldd
fails on shells other than Bash >= 3.0 because of the pipefail option
around try_trace (added on 2004-12-08). EGLIBC was patched in 2008 [2]
(r6912) to make the pipefail check run only on shells that support it,
but RTLD output would still be lost on other shells with certain SELinux
policies.
This patch rewrites try_trace to work on any POSIX-conformant shell in
such a way as to also work with such SELinux policies. It also obviates
one difference between glibc and EGLIBC.
URL: https://sourceware.org/ml/libc-alpha/2007-01/msg00041.html
URL: http://www.eglibc.org/archives/patches/msg00526.html
2013-09-11 P. J. McDermott <pj@pehjota.net>
[BZ #832]
* elf/ldd.bash.in (try_trace): More robustly and portably work around
SELinux terminal write permissions by using a command substitution
instead of a pipeline and pipefail option.
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Statically built binaries use __pointer_chk_guard_local,
while dynamically built binaries use __pointer_chk_guard.
Provide the right definition depending on the test case
we are building.
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The pointer guard used for pointer mangling was not initialized for
static applications resulting in the security feature being disabled.
The pointer guard is now correctly initialized to a random value for
static applications. Existing static applications need to be
recompiled to take advantage of the fix.
The test tst-ptrguard1-static and tst-ptrguard1 add regression
coverage to ensure the pointer guards are sufficiently random
and initialized to a default value.
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It has been a long practice for software using IEEE 754 floating-point
arithmetic run on MIPS processors to use an encoding of Not-a-Number
(NaN) data different to one used by software run on other processors.
And as of IEEE 754-2008 revision [1] this encoding does not follow one
recommended in the standard, as specified in section 6.2.1, where it
is stated that quiet NaNs should have the first bit (d1) of their
significand set to 1 while signalling NaNs should have that bit set to
0, but MIPS software interprets the two bits in the opposite manner.
As from revision 3.50 [2][3] the MIPS Architecture provides for
processors that support the IEEE 754-2008 preferred NaN encoding format.
As the two formats (further referred to as "legacy NaN" and "2008 NaN")
are incompatible to each other, tools have to provide support for the
two formats to help people avoid using incompatible binary modules.
The change is comprised of two functional groups of features, both of
which are required for correct support.
1. Dynamic linker support.
To enforce the NaN encoding requirement in dynamic linking a new ELF
file header flag has been defined. This flag is set for 2008-NaN
shared modules and executables and clear for legacy-NaN ones. The
dynamic linker silently ignores any incompatible modules it
encounters in dependency processing.
To avoid unnecessary processing of incompatible modules in the
presence of a shared module cache, a set of new cache flags has been
defined to mark 2008-NaN modules for the three ABIs supported.
Changes to sysdeps/unix/sysv/linux/mips/readelflib.c have been made
following an earlier code quality suggestion made here:
http://sourceware.org/ml/libc-ports/2009-03/msg00036.html
and are therefore a little bit more extensive than the minimum
required.
Finally a new name has been defined for the dynamic linker so that
2008-NaN and legacy-NaN binaries can coexist on a single system that
supports dual-mode operation and that a legacy dynamic linker that
does not support verifying the 2008-NaN ELF file header flag is not
chosen to interpret a 2008-NaN binary by accident.
2. Floating environment support.
IEEE 754-2008 features are controlled in the Floating-Point Control
and Status (FCSR) register and updates are needed to floating
environment support so that the 2008-NaN flag is set correctly and
the kernel default, inferred from the 2008-NaN ELF file header flag
at the time an executable is loaded, respected.
As the NaN encoding format is a property of GCC code generation that is
both a user-selected GCC configuration default and can be overridden
with GCC options, code that needs to know what NaN encoding standard it
has been configured for checks for the __mips_nan2008 macro that is
defined internally by GCC whenever the 2008-NaN mode has been selected.
This mode is determined at the glibc configuration time and therefore a
few consistency checks have been added to catch cases where compilation
flags have been overridden by the user.
The 2008 NaN set of features relies on kernel support as the in-kernel
floating-point emulator needs to be aware of the NaN encoding used even
on hard-float processors and configure the FPU context according to the
value of the 2008 NaN ELF file header flag of the executable being
started. As at this time work on kernel support is still in progress
and the relevant changes have not made their way yet to linux.org master
repository.
Therefore the minimum version supported has been artificially set to
10.0.0 so that 2008-NaN code is not accidentally run on a Linux kernel
that does not suppport it. It is anticipated that the version is
adjusted later on to the actual initial linux.org kernel version to
support this feature. Legacy NaN encoding support is unaffected, older
kernel versions remain supported.
[1] "IEEE Standard for Floating-Point Arithmetic", IEEE Computer
Society, IEEE Std 754-2008, 29 August 2008
[2] "MIPS Architecture For Programmers, Volume I-A: Introduction to the
MIPS32 Architecture", MIPS Technologies, Inc., Document Number:
MD00082, Revision 3.50, September 20, 2012
[3] "MIPS Architecture For Programmers, Volume I-A: Introduction to the
MIPS64 Architecture", MIPS Technologies, Inc., Document Number:
MD00083, Revision 3.50, September 20, 2012
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Long ago static startup did not parse the auxiliary vector and therefore
could not get at any `AT_FPUCW' tag to check whether upon FPU context
allocation the kernel would use a FPU control word setting different to
that provided by the `__fpu_control' variable. Static startup therefore
always initialized the FPU control word, forcing immediate FPU context
allocation even for binaries that otherwise never used the FPU.
As from GIT commit f8f900ecb9096ec47f5b7bb7626e29223c69061a static
startup supports parsing the auxiliary vector, so now it can avoid
explicit initialization of the FPU control word, just as can dynamic
startup, in the usual case where the setting written to the FPU control
word would be the same as the kernel uses. This defers FPU context
allocation until the binary itself actually pokes at the FPU.
Note that the `AT_FPUCW' tag is usually absent from the auxiliary vector
in which case _FPU_DEFAULT is assumed to be the kernel default.
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