| Commit message (Collapse) | Author | Age | Files | Lines |
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this is mainly for ABI compat purposes.
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this change is to align with a change in the glibc interface.
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patch by nsz. the actual object the caller has storing the tree root
has type void *, so accessing it as struct node * is not valid.
instead, simply access the value, move it to a temporary of the
appropriate type and work from there, then move the result back.
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check in configure to be polite (failing early if we're going to fail)
and in vfprintf.c since that is the point at which a mismatching type
would be extremely dangerous.
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it was already declared in stdlib.h, but not defined anywhere.
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this is a nonstandard extension.
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on newer kernels, fchdir and fstat work anyway. this same fix should
be applied to any other syscalls that are similarly affected.
with this change, the current definitions of O_SEARCH and O_EXEC as
O_PATH are mostly conforming to POSIX requirements. the main remaining
issue is that O_NOFOLLOW has different semantics.
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I intend to add more Linux workarounds that depend on using these
pathnames, and some of them will be in "syscall" functions that, from
an anti-bloat standpoint, should not depend on the whole snprintf
framework.
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previously, the AT_SYMLINK_NOFOLLOW flag was ignored, giving
dangerously incorrect behavior -- the target of the symlink had its
modes changed to the modes (usually 0777) intended for the symlink).
this issue was amplified by the fact that musl provides lchmod, as a
wrapper for fchmodat, which some archival programs take as a sign that
symlink modes are supported and thus attempt to use.
emulating AT_SYMLINK_NOFOLLOW was a difficult problem, and I
originally believed it could not be solved, at least not without
depending on kernels newer than 3.5.x or so where O_PATH works halfway
well. however, it turns out that accessing O_PATH file descriptors via
their pseudo-symlink entries in /proc/self/fd works much better than
trying to use the fd directly, and works even on older kernels.
moreover, the kernel has permanently pegged these references to the
inode obtained by the O_PATH open, so there should not be race
conditions with the file being moved, deleted, replaced, etc.
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this is the modern way, and the only way that makes any sense. glibc
has this complicated mechanism with RPATH and RUNPATH that controls
whether RPATH is processed before or after LD_LIBRARY_PATH, presumably
to support legacy binaries, but there is no compelling reason to
support this, and better behavior is obtained by just fixing the
search order.
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this fixes an oversight in the previous commit.
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previously, errno could be meaningless when the caller wrote it to the
dlerror string or stderr. try to make it meaningful. also, fix
incorrect check for over-long program headers and instead actually
support them by allocating memory if needed.
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this can only happen for invalid library files, but they were not
detected reliably because the variable was uninitialized.
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the access function cannot be used to check for existence, because it
operates using real uid/gid rather than effective to determine
accessibility; this matters for the non-final path components.
instead, use stat. failure of stat is success if only the final
component is missing (ENOENT) and otherwise is failure.
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also refactor mkdtemp based on new shared temp code, removing
dependency on the deprecated mktemp, whose behavior made this logic
more difficult.
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the concept of both versions is the same; they differ only in details.
for long runs, they use "rep movsl" or "rep movsq", and for small
runs, they use a trick, writing from both ends towards the middle,
that reduces the number of branches needed. in addition, if memset is
called multiple times with the same length, all branches will be
predicted; there are no loops.
for larger runs, there are likely faster approaches than "rep", at
least on some cpu models. for 32-bit, it's unlikely that there is any
faster approach that does not require non-baseline instructions; doing
anything fancier would require inspecting cpu capabilities. for
64-bit, there may very well be faster versions that work on all
models; further optimization could be explored in the future.
with these changes, memset is anywhere between 50% faster and 6 times
faster, depending on the cpu model and the length and alignment of the
destination buffer.
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the original motivation for this patch was that qemu (and possibly
other syscall emulators) nop out madvise, resulting in an infinite
loop. however, there is another benefit to this change: madvise may
actually undo an explicit madvise the application intended for its
stack, whereas the mremap operation is a true nop. the logic here is
that mremap must fail if it cannot resize the mapping in-place, and
the caller knows that it cannot resize in-place because it knows the
next page of virtual memory is already occupied.
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one of the arguments to memcmp may be shorter than the length l-3, and
memcmp is under no obligation not to access past the first byte that
differs. instead use strncmp which conveys the correct semantics. the
performance difference is negligible here and since the code is only
use for shared libc, both functions are already linked anyway.
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the dev/inode for the main app and the dynamic linker ("interpreter")
are not available, so the subsequent checks don't work. in general we
don't want to make exact string matches to existing libraries prevent
loading new ones, since this breaks loading upgraded modules in
module-loading systems. so instead, special-case it.
the motivation for this fix is that calling dlopen on the names
returned by dl_iterate_phdr or walking the link map (obtained by
dlinfo) seem to be the only methods available to an application to
actually get a list of open dso handles.
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reject elf files which are not ET_EXEC/ET_DYN type as bad exec format,
and reject ET_EXEC files when they cannot be loaded at the correct
address, since they are not relocatable at runtime. the main practical
benefit of this is to make dlopen of the main program fail rather than
producing an unsafe-to-use handle.
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it's not clear to me why the linker even outputs these headers if they
are null, but apparently it does so. with the default startfiles, they
will never be null anyway, but this patch allows eliminating crti,
crtn, crtbegin, and crtend (leaving only crt1) if the toolchain is
using init_array/fini_array (or for a C-only, no-ctor environment).
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in signal() it is needed since __sigaction uses restrict in parameters
and sharing the buffer is technically an aliasing error. do the same
for the syscall, as at least qemu-user does not handle it properly.
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LC_GLOBAL_LOCALE refers to the global locale, controlled by setlocale,
not the thread-local locale in effect which these functions should be
using. neither LC_GLOBAL_LOCALE nor 0 has an argument to the *_l
functions has behavior defined by the standard, but 0 is a more
logical choice for requesting the callee to lookup the current locale.
in the future I may move the current locale lookup the the caller (the
non-_l-suffixed wrapper).
at this point, all of the locale logic is dummied out, so no harm was
done, but it should at least avoid misleading usage.
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this change is in preparation for possibly adding support for the
field width and padding specifiers added in POSIX 2008.
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these odd names are actually generated by mess in glibc's stdlib.h, so
any glibc-linked program using strtol needs them to run against musl.
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entry point was wrong for PIE. e_entry was being treated as an
absolute value, whereas it's actually relative to the load address
(which is zero for non-PIE).
phdr pointer was wrong for non-PIE. e_phoff was being treated as
load-address-relative, whereas it's actually a file offset in the ELF
file. in any case, map_library was already computing it correctly, and
the incorrect code in __dynlink was overwriting it with junk.
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source and dest arguments for strcpy cannot overlap, so memmove must
be used here. the length is already known from the above loop.
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based on a patch by orc. POSIX actually fails to specify the format of
the ntop conversion; presumably, any output that will correctly
round-trip back via the (well-specified) pton operation is acceptable.
the new behavior is much more convenient than the old, however.
this patch also affects getnameinfo, which is implemented in terms of
inet_ntop and which is the preferred interface for performing this
conversion.
I've also removed some inexplicable cruft (filling the buffer with 'x'
before doing anything) whose origin I was unable to track down.
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this is a cheat since the _l versions take an extra argument, but
since these functions are only here for ABI purposes, it doesn't
really matter as long as the ABI matches. if the non-__-prefixed
versions are eventually made public, they should proabably be real
functions rather than hacks like this.
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unlike the strftime commit, this one is purely an ABI compatibility
issue. the previous version of the code would have worked just as well
with LC_TIME once LC_TIME support is added.
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the latter is both for ABI purposes, and to facilitate eventually
adding LC_TIME support. it's also nice to eliminate an extra source
file.
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based on a patch by orc, with indexing and flow control cleaned up a
little bit. this code is all going to be replaced at some point in the
near future.
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these are needed for some C++ library binaries including most builds
of libstdc++. I'm not entirely clear on the rationale. this patch does
not implement any special semantics for them, but as far as I can
tell, no special treatment is needed in correctly-linked programs;
this binding seems to exist only for catching incorrectly-linked
programs.
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this more than compensates for the size increase of jmp_buf, and
greatly reduces bss/data size on archs with huge jmp_buf.
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this is necessary to meet the C++ ABI target. alternatives were
considered to avoid the size increase for non-sig jmp_buf objects, but
they seemed to have worse properties. moreover, the relative size
increase is only extreme on x86[_64]; one way of interpreting this is
that, if the size increase from this patch makes jmp_buf use too much
memory, then the program was already using too much memory when built
for non-x86 archs.
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the case where mem was already aligned is handled earlier in the
function now.
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this bug was caught by the new footer-corruption check in realloc and
free.
if the block returned by malloc was already aligned to the desired
alignment, memalign's logic to split off the misaligned head was
incorrect; rather than writing to a point inside the allocated block,
it was overwriting the footer of the previous block on the heap with
the value 1 (length 0 plus an in-use flag).
fortunately, the impact of this bug was fairly low. (this is probably
why it was not caught sooner.) due to the way the heap works, malloc
will never return a block whose previous block is free. (doing so would
be harmful because it would increase fragmentation with no benefit.)
the footer is actually not needed for in-use blocks, except that its
in-use bit needs to remain set so that it does not get merged with
free blocks, so there was no harm in it being set to 1 instead of the
correct value.
however, there is one case where this bug could have had an impact: in
multi-threaded programs, if another thread freed the previous block
after memalign's call to malloc returned, but before memalign
overwrote the previous block's footer, the resulting block in the free
list could be left in a corrupt state. I have not analyzed the impact
of this bad state and whether it could lead to more serious
malfunction.
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since the old, poorly-thought-out musl approach to init/fini arrays on
ARM (when it was the only arch that needed them) was to put the code
in crti/crtn and have the legacy _init/_fini code run the arrays,
adding proper init/fini array support caused the arrays to get
processed twice on ARM. I'm not sure skipping legacy init/fini
processing is the best solution to the problem, but it works, and it
shouldn't break anything since the legacy init/fini system was never
used for ARM EABI.
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