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this requirement is tucked away in XSH 2.9.5 Thread Cancellation under
the heading Thread Cancellation Cleanup Handlers.
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a_store is only valid for int, but ssize_t may be defined as long or
another type. since there is no valid way for another thread to acess
the return value without first checking the error/completion status of
the aiocb anyway, an atomic store is not necessary.
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this allows getgrnam and getgrgid to share code with the _r versions
in preparation for alternate backend support.
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previously, aio operations were not tracked by file descriptor; each
operation was completely independent. this resulted in non-conforming
behavior for non-seekable/append-mode writes (which are required to be
ordered) and made it impossible to implement aio_cancel, which in turn
made closing file descriptors with outstanding aio operations unsafe.
the new implementation is significantly heavier (roughly twice the
size, and seems to be slightly slower) and presently aims mainly at
correctness, not performance.
most of the public interfaces have been moved into a single file,
aio.c, because there is little benefit to be had from splitting them.
whenever any aio functions are used, aio_cancel and the internal
queue lifetime management and fd-to-queue mapping code must be linked,
and these functions make up the bulk of the code size.
the close function's interaction with aio is implemented with weak
alias magic, to avoid pulling in heavy aio cancellation code in
programs that don't use aio, and the expensive cancellation path
(which includes signal blocking) is optimized out when there are no
active aio queues.
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the character sequence '$((' was incorrectly interpreted as the
opening of arithmetic even within single-quoted contexts, thereby
suppressing the checks for bad characters after the closing quote.
presently bad character checking is only performed when the WRDE_NOCMD
is used; this patch only corrects checking in that case.
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this allows getpwnam and getpwuid to share code with the _r versions
in preparation for alternate backend support.
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The code does a potentially misaligned 8-byte store to fill the tail
of the buffer. Then it fills the initial part of the buffer
which is a multiple of 8 bytes.
Therefore, if size is divisible by 8, we were storing last word twice.
This patch decrements byte count before dividing it by 8,
making one less store in "size is divisible by 8" case,
and not changing anything in all other cases.
All at the cost of replacing one MOV insn with LEA insn.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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"and $0xff,%esi" is a six-byte insn (81 e6 ff 00 00 00), can use
4-byte "movzbl %sil,%esi" (40 0f b6 f6) instead.
64-bit imul is slow, move it as far up as possible so that the result
(rax) has more time to be ready by the time we start using it
in mem stores.
There is no need to shuffle registers in preparation to "rep movs"
if we are not going to take that code path. Thus, patch moves
"jump if len < 16" instructions up, and changes alternate code path
to use rdx and rdi instead of rcx and r8.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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the name was recently added for the setxid/synccall rework,
so use the name now that we have it.
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just defining the necessary constants:
LD_B1B_MAX is 2^113 - 1 in base 10^9
KMAX is 2048 so the x array can hold up to 18432 decimal digits
(the worst case is converting 2^-16495 = 5^16495 * 10^-16495 to
binary, it requires the processing of int(log10(5)*16495)+1 = 11530
decimal digits after discarding the leading zeros, the conversion
requires some headroom in x, but KMAX is more than enough for that)
However this code is not optimal on archs with IEEE binary128
long double because the arithmetics is software emulated (on
all such platforms as far as i know) which means big and slow
strtod.
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This trivial copy-paste bug went unnoticed due to lack of testing.
No currently supported target archs are affected.
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armhf fesetenv implementation did a useless read of the fpscr.
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mips fesetenv did not handle FE_DFL_ENV, now fcsr is cleared in that
case.
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The sign bit was not cleared before checking for 0 so -0.0
was misclassified as FP_SUBNORMAL instead of FP_ZERO.
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all socket types are accepted at this point, but that may be changed
at a later time if the behavior is not meaningful for other types. as
before, omitting type (a value of 0) gives both UDP and TCP results,
and SOCK_DGRAM or SOCK_STREAM restricts to UDP or TCP, respectively.
for other socket types, the service name argument is required to be a
null pointer, and the protocol number provided by the caller is used.
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x86_64 syscall.h defined some musl internal syscall names and made
them public. These defines were already moved to src/internal/syscall.h
(except for SYS_fadvise which is added now) so the cruft in x86_64
syscall.h is not needed.
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in the case where a non-symlink file was replaced by a symlink during
the fchmodat operation with AT_SYMLINK_NOFOLLOW, mode change on the
new symlink target was successfully suppressed, but the error was not
reported. instead, fchmodat simply returned 0.
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the specification for execvp itself is unclear as to whether
encountering a file that cannot be executed due to EACCES during the
PATH search is a mandatory error condition; however, XBD 8.3's
specification of the PATH environment variable clarifies that the
search continues until a file with "appropriate execution permissions"
is found.
since it seems undesirable/erroneous to report ENOENT rather than
EACCES when an early path element has a non-executable file and all
later path elements lack any file by the requested name, the new code
stores a flag indicating that EACCES was seen and sets errno back to
EACCES in this case.
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in practice this was probably a non-issue, because the necessary
barrier almost certainly exists in kernel space -- implementing signal
delivery without such a barrier seems impossible -- but for the sake
of correctness, it should be done here too.
in principle, without a barrier, it is possible that the thread to be
cancelled does not see the store of its cancellation flag performed by
another thread. this affects both the case where the signal arrives
before entering the critical program counter range from __cp_begin to
__cp_end (in which case both the signal handler and the inline check
fail to see the value which was already stored) and the case where the
signal arrives during the critical range (in which case the signal
handler should be responsible for cancellation, but when it does not
see the cancellation flag, it assumes the signal is spurious and
refuses to act on it).
in the fix, the barrier is placed only in the signal handler, not in
the inline check at the beginning of the critical program counter
range. if the signal handler runs before the critical range is
entered, it will of course take no action, but its barrier will ensure
that the inline check subsequently sees the store. if on the other
hand the inline check runs first, it may miss seeing the store, but
the subsequent signal handler in the critical range will act upon the
cancellation request. this strategy avoids adding a memory barrier in
the common, non-cancellation code path.
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these are mandatory cancellation points per POSIX, so their omission
was a conformance bug.
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this typo did not result in an erroneous setjmp with at least binutils
2.22 but fix it for clarity and compatibility with potentially stricter
sh assemblers.
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when using /etc/shadow (rather than tcb) as its backend, getspnam_r
matched any username starting with the caller-provided string rather
than requiring an exact match. in practice this seems to have affected
only systems where one valid username is a prefix for another valid
username, and where the longer username appears first in the shadow
file.
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as a result of commit e8e4e56a8ce1f3d7e4a027ff5478f2f8ea70c46b,
the later code path for setting optarg to a null pointer is no longer
necessary, and removing it eliminates an indention level and arguably
makes the code more readable.
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the standard getopt does not touch optarg unless processing an option
with an argument. however, programs using the GNU getopt API, which we
attempt to provide in getopt_long, expect optarg to be a null pointer
after processing an option without an argument.
before argument permutation support was added, such programs typically
detected its absence and used their own replacement getopt_long,
masking the discrepency in behavior.
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multi-threaded set*id and setrlimit use the internal __synccall
function to work around the kernel's wrongful treatment of these
process properties as thread-local. the old implementation of
__synccall failed to be AS-safe, despite POSIX requiring setuid and
setgid to be AS-safe, and was not rigorous in assuring that all
threads were caught. in a worst case, threads late in the process of
exiting could retain permissions after setuid reported success, in
which case attacks to regain dropped permissions may have been
possible under the right conditions.
the new implementation of __synccall depends on the presence of
/proc/self/task and will fail if it can't be opened, but is able to
determine that it has caught all threads, and does not use any locks
except its own. it thereby achieves AS-safety simply by blocking
signals to preclude re-entry in the same thread.
with this commit, all known conformance and safety issues in set*id
functions should be fixed.
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per POSIX, the EINTR condition is an optional error for these
functions, not a mandatory one. since old kernels (pre-2.6.22) failed
to honor SA_RESTART for the futex syscall, it's dangerous to trust
EINTR from the kernel. thankfully POSIX offers an easy way out.
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in the current version of __synccall, the callback is always run, so
failure to handle this case did not matter. however, the upcoming
overhaul of __synccall will have failure cases, in which case the
callback does not run and errno is already set. the changes being
committed now are in preparation for that.
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this addresses alpine linux issue #3692 and brings the syslog message
length limit in alignment with uclibc's implementation.
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the code being removed was introduced to work around "partial failure"
of multi-threaded set*id() operations, where some threads would
succeed in changing their ids but an RLIMIT_NPROC setting would
prevent the rest from succeeding, leaving the process in an
inconsistent and dangerous state. however, the workaround code did not
handle important usage cases like swapping real and effective uids
then restoring their original values, and the wrongful kernel
enforcement of RLIMIT_NPROC at setuid time was removed in Linux 3.1,
making the workaround obsolete.
since the partial failure still is dangerous on old kernels, and could
in principle happen on post-fix kernels as well if set*id() syscalls
fail for another spurious reason such as resource-related failures,
new code is added to detect and forcibly kill the process if/when such
a situation arises. future documentation releases should be updated to
reflect that setting RLIMIT_NPROC to RLIM_INFINITY is necessary to
avoid this forced-kill on old kernels. ideally, at some point the
kernel will get proper multi-threaded set*id() syscalls capable of
performing their actions atomically, and all of the userspace code to
emulate them can be treated as a fallback for outdated kernels.
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opening /dev/tty then using ttyname_r on it does not produce a
canonical terminal name; it simply yields "/dev/tty".
it would be possible to make ctermid determine the actual controlling
terminal device via field 7 of /proc/self/stat, but doing so would
introduce a buffer overflow into applications built with L_ctermid==9,
which glibc defines, adversely affecting the quality of ABI compat.
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commit b72cd07f176b876aa51864d93aa8101477b1d732 added support for a
this feature in getopt, but it was later broken in the case where
getopt_long is used as a side effect of the changes made in commit
91184c4f16b143107fa9935edebe5d2b20bd70d8, which prevented the
underlying getopt call from seeing the leading '-' or '+' character in
optstring.
this commit changes the logic in the getopt_long core to check for a
leading colon, possibly after the leading '-' or '+', without
depending on the latter having been skipped by the caller. a minor
incorrectness in the return value for one error condition in
getopt_long is also fixed when opterr has been set to zero but
optstring has no leading ':'.
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based on patch by Dima Krasner, with minor improvements for code size.
connect can fail if there is no listening syslogd, in which case a
useless socket was kept open, preventing subsequent syslog call from
attempting to connect again.
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based on discussion with and patches by Felix Janda. these changes
started as an effort to factor forkpty in terms of login_tty, which
returns an error and skips fd reassignment and closing if setting the
controlling terminal failed. the previous forkpty code was unable to
handle errors in the child, and did not attempt to; it just silently
ignored them. but this would have been unacceptable when switching to
using login_tty, since the child would start with the wrong stdin,
stdout, and stderr and thereby clobber the parent's files.
the new code uses the same technique as the posix_spawn implementation
to convey any possible error in the child to the parent so that the
parent can report failure to the caller. it is also safe against
thread cancellation and against signal delivery in the child prior to
the determination of success.
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being a nonstandard function, this isn't strictly necessary, but it's
inexpensive and avoids unpleasant surprises. eventually I would like
all functions in libc to be safe against cancellation, either ignoring
it or acting on it cleanly.
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not only is this semantically more correct; it also reduces code size
slightly by eliminating the need for the compiler to assume the
possibility of aliasing.
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this is undocumented but possibly expected behavior of GNU
getopt_long, and useful when error message printing has been
suppressed.
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some related changes are also made to getopt, and the return value of
getopt_long in the case of missing arguments is fixed.
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if writing the error message fails, POSIX requires that ferror(stderr)
be set. and as a function that operates on a stdio stream, getopt is
required to lock the stream it uses, stderr.
fwrite calls are used instead of fprintf since there is a demand from
some users not to pull in heavy stdio machinery via getopt. this
mimics the original code using write.
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this shaves off a useless syscall for getting the caller's pid and
brings raise into alignment with other functions which were adapted to
use tkill rather than tgkill.
commit 83dc6eb087633abcf5608ad651d3b525ca2ec35e documents the
rationale for this change, and in particular why the tgkill syscall is
useless for its designed purpose of avoiding races.
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formally, it seems a sign is only required when the '+' modifier
appears in the format specifier, in which case either '+' or '-' must
be present in the output. but the specification is written such that
an optional negative sign is part of the output format anyway, and the
simplest approach to fixing the problem is removing the code that was
suppressing the sign.
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the affected code was wrongly counting characters instead of bytes.
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this avoids assuming the presence of C11 macro definitions in the
public complex.h, which need changes potentially incompatible with the
way these macros are being used internally.
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based on patch by Timo Teräs, with some corrections to bounds checking
code and other minor changes.
while they are borderline scope creep, the functions added are fairly
small and are roughly the minimum code needed to use the results of
the res_query API without re-implementing error-prone DNS packet
parsing, and they are used in practice by some kerberos related
software and possibly other things. at this time there is no intent to
implement further nameser.h API functions.
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