previously, this usage could lead to a crash if the thread pointer was
still uninitialized, and otherwise would just cause the canary to be
zero (less secure).
before, only the first library that failed to load or symbol that
failed to resolve was reported, and then the dynamic linker
immediately exited. when attempting to fix a library compatibility
issue, this is about the worst possible behavior. now we print all
errors as they occur and exit at the very end if errors were
encountered.
if new shared mappings of files/devices/shared memory can be made
between the time a robust mutex is unlocked and its subsequent removal
from the pending slot in the robustlist header, the kernel can
inadvertently corrupt data in the newly-mapped pages when the process
terminates. i am fixing the bug by using the same global vm lock
mechanism that was used to fix the race condition with unmapping
barriers after pthread_barrier_wait returns.
this affects at least the case of very long inputs, but may also
affect shorter inputs that become long due to growth while upscaling.
basically, the logic for the circular buffer indices of the initial
base-10^9 digit and the slot one past the final digit, and for
simplicity of the loop logic, assumes an invariant that they're not
equal. the upscale loop, which can increase the length of the
base-10^9 representation, attempted to preserve this invariant, but
was actually only ensuring that the end index did not loop around past
the start index, not that the two never become equal.
the main (only?) effect of this bug was that subsequent logic treats
the excessively long number as having no digits, leading to junk
results.
this function never existed historically; since the float/double
functions it's based on are nonstandard and deprecated, there's really
no justification for its existence except that glibc has it. it can be
added back if there's ever really a need...
since this interface is rarely used, it's probably best to lean
towards keeping code size down anyway. one-character needles will
still be found immediately by the initial wcschr call anyway.
the strspn call was made for every format specifier and end-of-string,
even though the expected return value was 1-2 for normal usage.
replace with simple loop.
amusingly, this cuts more than 10% off the run time of printf("a"); on
the machine i tested it on.
sadly the same optimization is not possible for snprintf without
duplicating all the pseudo-FILE setup code, which is not worth it.
there are still some discussions going on about tweaking the code, but
at least thing brings us to the point of having something working in
the repository. hopefully the remaining major hashes (md5,sha) will
follow soon.
some minor changes to how hard-coded sets for thread-related purposes
are handled were also needed, since the old object sizes were not
necessarily sufficient. things have gotten a bit ugly in this area,
and i think a cleanup is in order at some point, but for now the goal
is just to get the code working on all supported archs including mips,
which was badly broken by linux rejecting syscalls with the wrong
sigset_t size.
unfortunately, a large portion of programs which call crypt are not
prepared for its failure and do not check that the return value is
non-null before using it. thus, always "succeeding" but giving an
unmatchable hash is reportedly a better behavior than failing on
error.
it was suggested that we could do this the same way as other
implementations and put the null-to-unmatchable translation in the
wrapper rather than the individual crypt modules like crypt_des, but
when i tried to do it, i found it was making the logic in __crypt_r
for keeping track of which hash type we're working with and whether it
succeeded or failed much more complex, and potentially error-prone.
the way i'm doing it now seems to have essentially zero cost, anyway.
not heavily tested, but the basics are working. the basic concept is
that the dynamic linker entry point code invokes a pure-PIC (no global
accesses) C function in reloc.h to perform the early GOT relocations
needed to make the dynamic linker itself functional, then invokes
__dynlink like on other archs. since mips uses some ugly arch-specific
hacks to optimize relocating the GOT (rather than just using the
normal DT_REL[A] tables like on other archs), the dynamic linker has
been modified slightly to support calling arch-specific relocation
code in reloc.h.
most of the actual mips-specific behavior was developed by reading the
output of readelf on libc.so and simple executable files. i could not
find good reference information on which relocation types need to be
supported or their semantics, so it's possible that some legitimate
usage cases will not work yet.
changing the string printed for the dso name is not a regression; the
old code was simply using the wrong dso name (head rather than the dso
currently being relocated). this will be fixed in a later commit.
not heavily tested, but at least they don't seem to break anything on
soft float targets with or without coprocessors. they check the auxv
AT_HWCAP flags to determine which coprocessor, if any, is available.
since the correct declaration was not visible, and since the
representation of the types wchar_t and wint_t always match, a
compiler would have to go out of its way to make this bug manifest,
but better to fix it anyway.
it's expected that this will be needed/useful only in asm, so I've
given it its own symbol that can be addressed in pc-relative ways from
asm rather than adding a field in the __libc structure which would
require hard-coding the offset wherever it's used.
this seems counter-intuitive since sem_trywait is supposed to just try
once, not wait for the semaphore. however, the retry loop is not a
wait. instead, it's to handle the case where the value changes due to
a simultaneous post or wait from another thread while the semaphore
value remains positive. in such a case, it's absolutely wrong for
sem_trywait to fail with EAGAIN because the semaphore is not busy.
based on patches by orc and Isaac Dunham, with some fixes. sys/io.h
exists and contains prototypes for these functions regardless of
whether the target arch has them; this is a bit unorthodox but I don't
think it will break anything. the function definitions do not exist
unless the appropriate SYS_* syscall number macro is defined, which
should make sure configure scripts looking for these functions don't
find them on other systems.
presently, sys/io.h does not have the inb/outb/etc. port io
macros/functions. I'd be surprised if ioperm/iopl are useful without
them, so they probably need to be added at some point in appropriate
bits/io.h files...
also fix the alignment of jmp_buf to meet the abi. linux always
emulates fpu on mips if it's not present, so enabling this code
unconditionally is "safe" but may be slow. in the long term it may be
preferable to find a way to disable it on soft float builds.
Rich Felker
nsz