We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date. Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.
Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions. These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.
The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively. These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:
https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dchttps://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Remove generic tlsdesc code related to lazy tlsdesc processing since
lazy tlsdesc relocation is no longer supported. This includes removing
GL(dl_load_lock) from _dl_make_tlsdesc_dynamic which is only called at
load time when that lock is already held.
Added a documentation comment too.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
These static functions are not needed if a target does not do lazy
tlsdesc initialization.
* elf/tlsdeschtab.h (_dl_tls_resolve_early_return_p): Mark unused.
(_dl_tlsdesc_wake_up_held_fixups): Likewise.
Lazy TLSDESC initialization needs to be synchronized with concurrent TLS
accesses. The TLS descriptor contains a function pointer (entry) and an
argument that is accessed from the entry function. With lazy initialization
the first call to the entry function updates the entry and the argument to
their final value. A final entry function must make sure that it accesses an
initialized argument, this needs synchronization on systems with weak memory
ordering otherwise the writes of the first call can be observed out of order.
There are at least two issues with the current code:
tlsdesc.c (i386, x86_64, arm, aarch64) uses volatile memory accesses on the
write side (in the initial entry function) instead of C11 atomics.
And on systems with weak memory ordering (arm, aarch64) the read side
synchronization is missing from the final entry functions (dl-tlsdesc.S).
This patch only deals with aarch64.
* Write side:
Volatile accesses were replaced with C11 relaxed atomics, and a release
store was used for the initialization of entry so the read side can
synchronize with it.
* Read side:
TLS access generated by the compiler and an entry function code is roughly
ldr x1, [x0] // load the entry
blr x1 // call it
entryfunc:
ldr x0, [x0,#8] // load the arg
ret
Various alternatives were considered to force the ordering in the entry
function between the two loads:
(1) barrier
entryfunc:
dmb ishld
ldr x0, [x0,#8]
(2) address dependency (if the address of the second load depends on the
result of the first one the ordering is guaranteed):
entryfunc:
ldr x1,[x0]
and x1,x1,#8
orr x1,x1,#8
ldr x0,[x0,x1]
(3) load-acquire (ARMv8 instruction that is ordered before subsequent
loads and stores)
entryfunc:
ldar xzr,[x0]
ldr x0,[x0,#8]
Option (1) is the simplest but slowest (note: this runs at every TLS
access), options (2) and (3) do one extra load from [x0] (same address
loads are ordered so it happens-after the load on the call site),
option (2) clobbers x1 which is problematic because existing gcc does
not expect that, so approach (3) was chosen.
A new _dl_tlsdesc_return_lazy entry function was introduced for lazily
relocated static TLS, so non-lazy static TLS can avoid the synchronization
cost.
[BZ #18034]
* sysdeps/aarch64/dl-tlsdesc.h (_dl_tlsdesc_return_lazy): Declare.
* sysdeps/aarch64/dl-tlsdesc.S (_dl_tlsdesc_return_lazy): Define.
(_dl_tlsdesc_undefweak): Guarantee TLSDESC entry and argument load-load
ordering using ldar.
(_dl_tlsdesc_dynamic): Likewise.
(_dl_tlsdesc_return_lazy): Likewise.
* sysdeps/aarch64/tlsdesc.c (_dl_tlsdesc_resolve_rela_fixup): Use
relaxed atomics instead of volatile and synchronize with release store.
(_dl_tlsdesc_resolve_hold_fixup): Use relaxed atomics instead of
volatile.
* elf/tlsdeschtab.h (_dl_tlsdesc_resolve_early_return_p): Likewise.
for ChangeLog
[BZ #17090]
[BZ #17620]
[BZ #17621]
[BZ #17628]
* NEWS: Update.
* elf/dl-tls.c (_dl_update_slotinfo): Clean up outdated DTV
entries with Static TLS too. Skip entries past the end of the
allocated DTV, from Alan Modra.
(tls_get_addr_tail): Update to glibc_likely/unlikely. Move
Static TLS DTV entry set up from...
(_dl_allocate_tls_init): ... here (fix modid assertion), ...
* elf/dl-reloc.c (_dl_nothread_init_static_tls): ... here...
* nptl/allocatestack.c (init_one_static_tls): ... and here...
* elf/dlopen.c (dl_open_worker): Drop l_tls_modid upper bound
for Static TLS.
* elf/tlsdeschtab.h (map_generation): Return size_t. Check
that the slot we find is associated with the given map before
using its generation count.
* nptl_db/db_info.c: Include ldsodefs.h.
(rtld_global, dtv_slotinfo_list, dtv_slotinfo): New typedefs.
* nptl_db/structs.def (DB_RTLD_VARIABLE): New macro.
(DB_MAIN_VARIABLE, DB_RTLD_GLOBAL_FIELD): Likewise.
(link_map::l_tls_offset): New struct field.
(dtv_t::counter): Likewise.
(rtld_global): New struct.
(_rtld_global): New rtld variable.
(dl_tls_dtv_slotinfo_list): New rtld global field.
(dtv_slotinfo_list): New struct.
(dtv_slotinfo): Likewise.
* nptl_db/td_symbol_list.c: Drop gnu/lib-names.h include.
(td_lookup): Rename to...
(td_mod_lookup): ... this. Use new mod parameter instead of
LIBPTHREAD_SO.
* nptl_db/td_thr_tlsbase.c: Include link.h.
(dtv_slotinfo_list, dtv_slotinfo): New functions.
(td_thr_tlsbase): Check DTV generation. Compute Static TLS
addresses even if the DTV is out of date or missing them.
* nptl_db/fetch-value.c (_td_locate_field): Do not refuse to
index zero-length arrays.
* nptl_db/thread_dbP.h: Include gnu/lib-names.h.
(td_lookup): Make it a macro implemented in terms of...
(td_mod_lookup): ... this declaration.
* nptl_db/db-symbols.awk (DB_RTLD_VARIABLE): Override.
(DB_MAIN_VARIABLE): Likewise.
