A variant of this new lock algorithm has been presented at SAC'16, see
https://hal.inria.fr/hal-01304108. A full version of that paper is
available at https://hal.inria.fr/hal-01236734.
The main motivation of this is to improve on the safety of the basic lock
implementation in musl. This is achieved by squeezing a lock flag and a
congestion count (= threads inside the critical section) into a single
int. Thereby an unlock operation does exactly one memory
transfer (a_fetch_add) and never touches the value again, but still
detects if a waiter has to be woken up.
This is a fix of a use-after-free bug in pthread_detach that had
temporarily been patched. Therefore this patch also reverts
c1e27367a9b26b9baac0f37a12349fc36567c8b6
This is also the only place where internal knowledge of the lock
algorithm is used.
The main price for the improved safety is a little bit larger code.
Under high congestion, the scheduling behavior will be different
compared to the previous algorithm. In that case, a successful
put-to-sleep may appear out of order compared to the arrival in the
critical section.
With Linux kernel 4.16 it will be possible to guard more parts of the
Linux header files from a libc. Make use of this in musl to guard all
the structures and other definitions from the Linux header files which
are also defined by the header files provided by musl. This will make
it possible to compile source files which include both the libc
headers and the kernel userspace headers.
This extends the definitions done in commit 04983f227238 ("make
netinet/in.h suppress clashing definitions from kernel headers")
previously, the charset names without endianness specified were always
interpreted as big endian. unicode specifies that UTF-16 and UTF-32
have BOM-determined endianness if BOM is present, and are otherwise
big endian. since commit 5b546faa67544af395d6407553762b37e9711157
added support for stateful encodings, it is now possible to implement
BOM support via the conversion descriptor state.
for conversions to these charsets, the output is always big endian and
does not have a BOM.
the mapping tables and code are not automatically generated; they were
produced by comparing the output of towupper/towlower against the
mappings in the UCD, ignoring characters that were previously excluded
from case mappings or from alphabetic status (micro sign and circled
letters), and adding table entries or code for everything else
missing.
based very loosely on a patch by Reini Urban.
the new version of the code used to generate these tables forces a
newline every 256 entries, whereas at the time these files were
originally generated and committed, it only wrapped them at 80
columns. the new behavior ensures that localized changes to the
tables, if they are ever needed, will produce localized diffs.
commit d060edf6c569ba9df4b52d6bcd93edde812869c9 made the corresponding
changes to the iconv tables.
notes by maintainer:
commit 2f853dd6b9a95d5b13ee8f9df762125e0588df5d added these rules
because the new system for handling arch-provided replacement files
introduced for out-of-tree builds did not apply to the crt tree.
commit 63bcda4d8f4074e9d92ae156afd0dced6e64eb65 later adapted the
makefile logic so that the crt and ldso trees go through the same
replacement logic as everything else, but failed to remove the
explicit rules that assumed the arch would always provide asm
replacements.
in addition to cleaning things up, removing these spurious rules
allows crti/crtn asm to be omitted by an arch (thereby using the empty
C files instead) if they are not needed.
notes by maintainer:
both C and POSIX use the term UTC to specify related functionality,
despite POSIX defining it as something more like UT1 or historical
(pre-UTC) GMT without leap seconds. neither specifies the associated
string for %Z. old choice of "GMT" violated principle of least
surprise for users and some applications/tests. use "UTC" instead.
aside from theoretical arbitrary results due to UB, this could
practically cause unbounded overflow of static array if hit, but
hitting it depends on having more than 32 calls to at_quick_exit and
having them sufficiently often.
notes added by maintainer:
the '-' specifier allows default padding to be suppressed, and '_'
allows padding with spaces instead of the default (zeros).
these extensions seem to be included in several other implementations
including FreeBSD and derivatives, and Solaris. while portable
software should not depend on them, time format strings are often
exposed to the user for configurable time display. reportedly some
python programs also use and depend on them.
notes added by maintainer:
this function is a GNU extension. it was chosen over the similar BSD
function funopen because the latter depends on fpos_t being an
arithmetic type as part of its public API, conflicting with our
definition of fpos_t and with the intent that it be an opaque type. it
was accepted for inclusion because, despite not being widely used, it
is usually very difficult to extricate software using it from the
dependency on it.
calling pattern for the read and write callbacks is not likely to
match glibc or other implementations, but should work with any
reasonable callbacks. in particular the read function is never called
without at least one byte being needed to satisfy its caller, so that
spurious blocking is not introduced.
contracts for what callbacks called from inside libc/stdio can do are
always complicated, and at some point still need to be specified
explicitly. at the very least, the callbacks must return or block
indefinitely (they cannot perform nonlocal exits) and they should not
make calls to stdio using their own FILE as an argument.
previously, fgetwc left all but the first byte of an illegal sequence
unread (available for subsequent calls) when reading out of the FILE
buffer, but dropped all bytes contibuting to the error when falling
back to reading a byte at a time. neither behavior was ideal. in the
buffered case, each malformed character produced one error per byte,
rather than one per character. in the unbuffered case, consuming the
last byte that caused the transition from "incomplete" to "invalid"
state potentially dropped (and produced additional spurious encoding
errors for) the next valid character.
to handle both cases uniformly without duplicate code, revise the
buffered case to only cover situations where a complete and valid
character is present in the buffer, and fall back to byte-at-a-time
for all other cases. this allows using mbtowc (stateless) instead of
mbrtowc, which may slightly improve performance too.
when an encoding error has been hit in the byte-at-a-time case, leave
the final byte that produced the error unread (via ungetc) except in
the case of single-byte errors (for UTF-8, bytes c0, c1, f5-ff, and
continuation bytes with no lead byte). single-byte errors are fully
consumed so as not to leave the caller in an infinite loop repeating
the same error.
none of these changes are distinguished from a conformance standpoint,
since the file position is unspecified after encoding errors. they are
intended merely as QoI/consistency improvements.
fgetwc does not set the stream's error indicator on encoding errors,
making ferror insufficient to distinguish between error and eof
conditions. feof is also insufficient, since it will return true if
the file ended with a partial character encoding error.
whether fgetwc should be setting the error indicator itself is a
question with conflicting answers. the POSIX text for the function
states it as a requirement, but the ISO C text seems to require that
it not. this may be revisited in the future based on the outcome of
Austin Group issue #1170.
these encodings are still commonly used in messaging protocols and
such. the reverse mapping is implemented as a binary search of a list
of the jis 0208 characters in unicode order; the existing forward
table is used to perform the comparison in the search.
previously, 8-bit codepages could only remap the high 128 bytes; the
low range was assumed/forced to agree with ascii. interpretation of
codepage table headers has been changed so that it's possible to
represent mappings for up to 256 slots (fewer if the initial portion
of the map is elided because it coincides with unicode codepoints).
this requires consuming a bit more of the 10-bit space of characters
that can be represented in 8-bit codepages, but there's still a plenty
left. the size of the legacy_chars table is actually reduced now by
eliding the first 256 entries and considering them to map implicitly
via the identity map.
before these changes, there seem to have been minor bugs/omissions in
codepage table generation, so it's likely that some actual bug fixes
are silently included in this commit. round-trip testing of a few
codepages was performed on the new version of the code, but no
differential testing against the old version was done.
commit c49d3c8adadfa24235fcf4779bb722b1aa6f480b added logic to detect
attempts to load libc.so via another name and instead redirect to the
existing libc, rather than loading two and producing dangerously
inconsistent state. however, the check for and unmapping of the
duplicate libc happened after reclaim_gaps was already called,
donating the slack space around the writable segment to malloc.
subsequent unmapping of the library then invalidated malloc's free
lists.
fix the issue by moving the call to reclaim_gaps out of map_library
into load_library, after the duplicate libc check but before the first
call to calloc, so that the gaps can still be used to satisfy the
allocation of struct dso. this change also eliminates the need for an
ugly hack (temporarily setting runtime=1) to avoid reclaim_gaps when
loading the main program via map_library, which happens when ldso is
invoked as a command.
only programs/libraries erroneously containing a DT_NEEDED reference
to libc.so via an absolute pathname or symlink were affected by this
issue.
the new version of the code used to generate these tables forces a
newline every 256 entries, whereas at the time these files were
originally generated and committed, it only wrapped them at 80
columns. the new behavior ensures that localized changes to the
tables, if they are ever needed, will produce localized diffs. other
tables including hkscs were already committed in the new format.
binary comparison of the generated object files was performed to
confirm that no spurious changes slipped in.
If the syscall fails, errno must be set correctly for the caller.
There's no guarantee that the handlers registered with pthread_atfork
won't clobber errno, so we need to ensure it gets set after they are
called.
this implementation aims to match the baseline defined by rfc1468 (the
original mime charset definition) plus the halfwidth katakana
extension included in the whatwg definition of the charset. rejection
of si/so controls and newlines in doublebyte state are not currently
enforced. the jis x 0201 mode is currently interpreted as having the
yen sign and overline character in place of backslash and tilde; ascii
mode has the standard ascii characters in those slots.
assuming pointers obtained from malloc have some nonzero alignment,
repurpose the low bit of iconv_t as an indicator that the descriptor
is a stateless value representing the source and destination character
encodings.
the special case where mbrtowc returns 0 but consumed 1 byte of input
does not need to be considered, because the short-circuit for low
bytes already covered that case.
short-circuiting low bytes before the switch precluded support for
character encodings that don't coincide with ascii in this range. this
limitation affected iso-2022 encodings, which use the esc byte to
introduce a shift sequence, and things like ebcdic.
this is in preparation to support stateful conversion descriptors,
which are necessarily allocated and thus must be freed in iconv_close.
putting it in a separate TU will avoid pulling in free if iconv_close
is not referenced.
this change is made to avoid having assumptions about the encoding
spread out across the file, and to facilitate future change to a form
that can accommodate allocted, stateful descriptors when needed.
this commit should not produce any functional changes; with the
compiler tested the only change to code generation was minor
reordering of local variables on stack.
If AI_NUMERICSERV is specified and a numeric service was not provided,
POSIX mandates getaddrinfo return EAI_NONAME. EAI_SERVICE is only for
services that cannot be used on the specified socket type.
commit a6054e3c94aa0491d7366e4b05ae0d73f661bfe2 changed this function
not to take an argument, but the weak definition used by timer_create
was not updated to match.
reported by Pascal Cuoq.
s390 can use the generic ioctls definitions other than FIOQSIZE (like arm).
this fixes some missing ioctls and two incorrect ones:
TIOCTTYGSTRUCT and TIOCM_MODEM_BITS seem to be defined on frv
target only in linux.
for getting/setting write lifetime hints fcntl commands were
added in linux commit c75b1d9421f80f4143e389d2d50ddfc8a28c8c35
added under _GNU_SOURCE || _BSD_SOURCE, since RWH_* life time
hints are not in the POSIX reserved namespace.
hwcap bits for armv8.3 extensions, added in linux commits
c8c3798d2369e4285da44b244638eafe446a8f8a
cb567e79fa504575cb97fb2f866d2040ed1c92e7
c651aae5a7732287c1c9bc974ece4ed798780544
SO_MEMINFO added in linux commit a2d133b1d465016d0d97560b11f54ba0ace56d3e
SO_INCOMING_NAPI_ID added in 6d4339028b350efbf87c61e6d9e113e5373545c9
SO_COOKIE added in 5daab9db7b65df87da26fd8cfa695fb9546a1ddb
