Rich Felker [Thu, 15 Oct 2015 16:08:51 +0000 (12:08 -0400)]
prevent reordering of or1k and powerpc thread pointer loads
other archs use asm for the thread pointer load, so making that asm
volatile is sufficient to inform the compiler that it has a "side
effect" (crashing or giving the wrong result if the thread pointer was
not yet initialized) that prevents reordering. however, powerpc and
or1k have dedicated general purpose registers for the thread pointer
and did not need to use any asm to access it; instead, "local register
variables with a specified register" were used. however, there is no
specification for ordering constraints on this type of usage, and
presumably use of the thread pointer could be reordered across its
initialization.
to impose an ordering, I have added empty volatile asm blocks that
produce the "local register variable with a specified register" as
an output constraint.
Rich Felker [Wed, 14 Oct 2015 21:08:34 +0000 (17:08 -0400)]
remove hand-written crt1.s and Scrt1.s files for all archs
since commit c5e34dabbb47d8e97a4deccbb421e0cd93c0094b, crt1.c has
provided a "mostly-C" implementation of the crt1 start file that
avoids the need for arch-specific symbol referencing, PIC/PIE-specific
code variants, etc. but for archs that had existing hand-written
versions, the new code was initially unused, and later only used as
the dynamic linker entry point. this commit switches all archs to
using the new code.
the code being removed was a recurring source of subtle errors, and
was still broken at least on arm, where it failed to properly align
the stack pointer before calling into C code.
Rich Felker [Thu, 8 Oct 2015 23:30:42 +0000 (23:30 +0000)]
fix integer overflows in time_t/struct tm conversion code
as found and reported by Brian Mastenbrook, the expressions
400*qc_cycles and years+100 in __secs_to_tm were both subject to
integer overflow for extreme values of the input t.
this patch by Szabolcs Nagy fixes the code by switching to larger
types, and matches the original intent I had in mind when writing this
code.
Rich Felker [Thu, 8 Oct 2015 22:03:53 +0000 (22:03 +0000)]
fix open_[w]memstream behavior when no writes take place
the specification for these functions requires that the buffer/size
exposed to the caller be valid after any successful call to fflush or
fclose on the stream. the implementation's approach is to update them
only at flush time, but that misses the case where fflush or fclose is
called without any writes having taken place, in which case the write
flushing callback will not be called.
to fix both the observable bug and the desired invariant, setup empty
buffers at open time and fail the open operation if no memory is
available.
Alex Dowad [Fri, 2 Oct 2015 11:32:33 +0000 (13:32 +0200)]
fix instruction matching errors in i386 CFI generation
fdiv and fmul instructions were wrongly matched by the rules for
integer div and mul instructions, leading to incorrect conclusions
about register values being clobbered.
Alex Dowad [Fri, 2 Oct 2015 11:32:32 +0000 (13:32 +0200)]
factor common awk functions for CFI generation scripts into new file
There is a lot which could be common between i386 and x86_64, but none
of it will be useful for any other arch. These should be useful for
all archs, however.
Rich Felker [Thu, 1 Oct 2015 22:59:56 +0000 (22:59 +0000)]
make nl_langinfo(CODESET) always return "ASCII" in byte-based C locale
commit 844212d94f582c4e3c5055e0a1524931e89ebe76, which did not make it
into any releases, changed nl_langinfo(CODESET) to always return
"UTF-8", even in the byte-based C locale. this was problematic because
application software was found to use the string match for "UTF-8" to
activate its own UTF-8 processing. this both undermines the byte-based
functionality of the C locale, and if mixed with with calls to the
standard multibyte functions, which happened in practice, could result
in severe mis-handling of input.
the motive for the previous change was that, to avoid widespread
compatibility problems, the string returned by nl_langinfo(CODESET)
needs to be accepted by iconv and by third-party character conversion
code. thus, the only remaining choice is "ASCII". this choice
accurately represents the intent that high bytes do not have
individual meaning in the C locale, but it does mean that iconv, when
passed nl_langinfo(CODESET) in the C locale, will produce errors in
cases where mbrtowc would have succeeded. for reference, glibc behaves
similarly in this regard, so I don't think it will be a problem.
eliminate protected-visibility data in libc.so with vis.h preinclude
some newer binutils versions print scary warnings about protected data
because most gcc versions fail to produce the right address
references/relocations for such data that might be subject to copy
relocations. originally vis.h explicitly assigned default visibility
to all public data symbols to avoid this issue, but commit b8dda24fe1caa901a99580f7a52defb95aedb67c removed this treatment for
stdin/out/err to work around a gcc 3.x bug, and since they don't
actually need it (because taking their addresses is not valid C).
instead, a check for the gcc 3.x bug is added to the configure check
for vis.h preinclude support; this feature will simply be disabled
when using a buggy version of gcc.
avoid attempting to lookup IP literals as hostnames
previously, __lookup_ipliteral only checked its argument against the
requested address family, so IPv4 literals passed through to
__lookup_name if the caller asked for only IPv6 results, and likewise
for IPv6 literals when the caller asked for only IPv4. this resulted
in spurious DNS lookups that reportedly even succeeded with some
nameservers.
now, __lookup_ipliteral attempts to parse its argument as both IPv4
and IPv6, and returns an error (to stop further search) rather than 0
(no results yet) if the form of the argument mismatches the requested
address family.
Szabolcs Nagy [Wed, 23 Sep 2015 20:22:33 +0000 (20:22 +0000)]
avoid reading uninitialized memory in __map_file
The value of *size is not relevant in case of failure, but it's
better not to copy garbage from the stack into it.
(The compiler cannot see through the syscall, so optimization
was not affected by the unspecified value).
the restorer function pointer provided in the kernel sigaction
structure is interpreted by the kernel as a raw code address, not a
function descriptor.
this commit moves the declarations of the __restore and __restore_rt
symbols to ksigaction.h so that arch versions of the file can override
them, and introduces a version for sh which declares them as objects
rather than functions.
an alternate solution would have been defining SA_RESTORER to 0 so
that the functions are not used, but this both requires executable
stack (since the sh kernel does not have a vdso page with permanent
restorer functions) and crashes on qemu user-level emulation.
lookup the dso an address falls in based on the loadmap and not just a
base/length. fix the main app's fake loadmap used when loaded by a
non-fdpic-aware loader so that it does not cover the whole memory
space.
function descriptor addresses are also matched for future use by
dladdr, but reverse lookups of function descriptors via dladdr have
not been implemented yet. some revisions may be needed in the future
once reclaim_gaps supports fdpic, so that function descriptors
allocated in reclaimed heap space do not get detected as belonging to
the module whose gaps they were allocated in.
previously these resolved to the code address rather than the address
of the function descriptor.
the conditions for accepting or rejecting symbols are quite
inconsistent between the different points in the dynamic linker code
where such decisions are made. this commit attempts to be at least as
correct as anything already there, but does not improve consistency.
it has been tested to correctly avoid symbols that are merely
references to functions defined in other modules, at least in simple
usage, but at some point all symbol lookup logic should be reviewed
and refactored/unified.
have sh/fdpic entry point set fdpic personality if needed
the entry point code supports being loaded by a loader which is not
fdpic-aware (in practice, either kernel with mmu or qemu without fdpic
support). this mostly just works, but signal handling will wrongly use
a function descriptor address as a code address if the personality is
not adjusted to fdpic.
ideally this code could be placed with sigaction so that it's not
needed except if/when a signal handler is installed. however,
personality is incorrectly maintained per-thread by the kernel, rather
than per-process, so it's necessary to correct the personality before
any threads are started. also, in order to skip the personality
syscall when an fdpic-aware loader is used, we need to be able to
detect how the program was loaded, and this information is only
readily available at the entry point.
move calls to application init functions after crt1 entry point
this change is needed to be compatible with fdpic, where some of the
main application's relocations may be performed as part of the crt1
entry point. if we call init functions before passing control, these
relocations will not yet have been performed, and the init code will
potentially make use of invalid pointers.
conceptually, no code provided by the application or third-party
libraries should run before the application entry point. the
difference is not observable to programs using the crt1 we provide,
but it could come into play if custom entry point code is used, so
it's better to be doing this right anyway.
previously, the normal ELF library loading code was used even for
fdpic, so only the kernel-loaded dynamic linker and main app could
benefit from separate placement of segments and shared text.
try to suppress linking libc.so if there are undefined symbols
this is always an error and usually results from failure to find/link
the compiler runtime library, but it could also result from
implementation errors in libc, using functions that don't (yet) exist.
either way the resulting libc.so will crash mysteriously at runtime.
the crash happens too early to produce a meaningful error, so these
crashes are very confusing to users and waste a lot of debugging time.
this commit should ensure that they do not happen.
the __fdpic_fixup code is not needed for ET_DYN executables, which
instead use reloctions, so we can omit it from the dynamic linker and
static-pie entry point and save some code size.
work around breakage in sh/fdpic __unmapself function
the C implementation of __unmapself used for potentially-nommu sh
assumed CRTJMP takes a function descriptor rather than a code address;
however, the actual dynamic linker needs a code address, and so commit 7a9669e977e5f750cf72ccbd2614f8b72ce02c4c changed the definition of the
macro in reloc.h. this commit puts the old macro back in a place where
it only affects __unmapself.
this is an ugly workaround and should be cleaned up at some point, but
at least it's well isolated.
add general fdpic support in dynamic linker and arch support for sh
at this point not all functionality is complete. the dynamic linker
itself, and main app if it is also loaded by the kernel, take
advantage of fdpic and do not need constant displacement between
segments, but additional libraries loaded by the dynamic linker follow
normal ELF semantics for mapping still. this fully works, but does not
admit shared text on nommu.
in terms of actual functional correctness, dlsym's results are
presently incorrect for function symbols, RTLD_NEXT fails to identify
the caller correctly, and dladdr fails almost entirely.
with the dynamic linker entry point working, support for static pie is
automatically included, but linking the main application as ET_DYN
(pie) probably does not make sense for fdpic anyway. ET_EXEC is
equally relocatable but more efficient at representing relocations.
factor symbol counting out of dladdr as its own function
the fdpic code will need to count symbols, and it may be useful
elsewhere in the future too. counting is trivial as long as sysv hash
is present, but for gnu-hash-only libraries it's complex.
the behavior of the count is changed slightly: we now include symbols
that are not accessible by the gnu hash table in the count. this may
make dladdr slightly slower. if this is a problem, dladdr can subtract
out the part that should not be accessible. unlike in the old code,
subtracting this out is easy even in the fast path where sysv hash is
available too.
further refactoring of dynamic linker load address computations
these are in do_relocs. the first one was omitted in commit 301335a80b85f12c018e4acf1a2c28615e119f8d because it slightly changes
code (using dso->base rather than cached local var base) and would
have prevented easy verification. the other was an oversight.
begin refactoring load address computations in dynamic linker
for ordinary ELF with fixed segment displacements, load address
computation is simply adding the base load address. but for FDPIC,
each segment has its own load address, and virtual addresses need to
be adjusted according to the segment they fall in. abstracting this
computation is the first step to making the dynamic linker ready for
FDPIC.
for this first commit, a macro is used rather than a function in order
to facilitate correctness checking. I have verified that the generated
code does not change on my i386 build.
remove old dlstart stage-2 symbolic lookup code; add new generic
this new generic version of the stage-2 function lookup should work
for any arch where static data is accessible via got-relative or
pc-relative addressing, using approximately the technique described in
the log message for commit 2907afb8dbd4c1d34825c3c9bd2b41564baca210.
since all the mips-like archs that need got slots fo access static
data have already transitioned to the new stage chaining scheme, the
old dynamic symbol lookup code is now removed.
aarch64, arm, and sh have not yet transitioned; with this commit, they
are now using the new generic code.
introduce new symbol-lookup-free rcrt1/dlstart stage chaining
previously, the call into stage 2 was made by looking up the symbol
name "__dls2" (which was chosen short to be easy to look up) from the
dynamic symbol table. this was no problem for the dynamic linker,
since it always exports all its symbols. in the case of the static pie
entry point, however, the dynamic symbol table does not contain the
necessary symbol unless -rdynamic/-E was used when linking. this
linking requirement is a major obstacle both to practical use of
static-pie as a nommu binary format (since it greatly enlarges the
file) and to upstream toolchain support for static-pie (adding -E to
default linking specs is not reasonable).
this patch replaces the runtime symbolic lookup with a link-time
lookup via an inline asm fragment, which reloc.h is responsible for
providing. in this initial commit, the asm is provided only for i386,
and the old lookup code is left in place as a fallback for archs that
have not yet transitioned.
modifying crt_arch.h to pass the stage-2 function pointer as an
argument was considered as an alternative, but such an approach would
not be compatible with fdpic, where it's impossible to compute
function pointers without already having performed relocations. it was
also deemed desirable to keep crt_arch.h as simple/minimal as
possible.
in principle, archs with pc-relative or got-relative addressing of
static variables could instead load the stage-2 function pointer from
a static volatile object. that does not work for fdpic, and is not
safe against reordering on mips-like archs that use got slots even for
static functions, but it's a valid on i386 and many others, and could
provide a reasonable default implementation in the future.
remove attribute((const)) from pthread_self and errno location decls
this attribute was applied to pthread_self and the functions providing
the locations for errno and h_errno as an optimization; however, it is
subtly incorrect. as specified, it means the return value will always
be the same, which is not true; it varies per-thread.
this attribute also implies that the function does not depend on any
state, and that calls to it can safely be reordered across any other
code. however such reordering is unsafe for these functions: they
break when reordered before initialization of the thread pointer. such
breakage was actually observed when compiled by libfirm/cparser.
to some extent the reordering problem could be solved with strong
compiler barriers between the stages of early startup code, but the
specified meaning of of attribute((const)) is sufficiently strong that
a compiler would theoretically be justified inserting gratuitous calls
to attribute((const)) const functions at random locations (e.g. to
save the value in static storage for later use).
add format argument attributes to gettext function prototypes
their absence completely breaks format string warnings in programs
with gettext message translations: -Wformat gives no results, and
-Wformat-nonliteral produces spurious warnings.
with gcc, the problem manifests only in standards-conforming profiles;
otherwise gcc sets these attributes by default for the gettext family.
with clang, the problem always manifests; clang has no such defaults.
with this commit it should be possible to produce a working
static-linked fdpic libc and application binaries for sh.
the changes in reloc.h are largely unused at this point since dynamic
linking is not supported, but the CRTJMP macro is used one place
outside of dynamic linking, in __unmapself.
this version of the entry point is only suitable for static linking in
ET_EXEC form. neither dynamic linking nor pie is supported yet. at
some point in the future the fdpic and non-fdpic versions of this code
may be unified but for now it's easiest to work with them separately.
clone calls back to a function pointer provided by the caller, which
will actually be a pointer to a function descriptor on fdpic. the
obvious solution is to have a separate version of clone for fdpic, but
I have taken a simpler approach to go around the problem. instead of
calling the pointed-to function from asm, a direct call is made to an
internal C function which then calls the pointed-to function. this
lets the C compiler generate the appropriate calling convention for an
indirect call with no need for ABI-specific assembly.
make sh crti/crtn init/fini fragments setup proper stack frame
for fdpic support is is essential that the got pointer be saved at a
known, ABI-dictated offset from the frame pointer, since there is no
way to recover it once it's lost.
fix missing earlyclobber flag in i386 a_ctz_64 asm
this error was only found by reading the code, but it seems to have
been causing gcc to produce wrong code in malloc: the same register
was used for the output and the high word of the input. in principle
this could have caused an infinite loop searching for an available
bin, but in practice most x86 models seem to implement the "undefined"
result of the bsf instruction as "unchanged".
remove unused (and invalid) C version of sigsetjmp
originally, the comment in this code was correct and it would likely
work if the compiler generated a tail call to setjmp. however, commit 583e55122e767b1586286a0d9c35e2a4027998ab redesigned sigsetjmp and
siglongjmp such that the old C implementation (which was not intended
to be used) is not even conceptually correct. remove it in the
interest of avoiding confusion when porting to new archs.
this restores the original behavior prior to the addition of the
byte-based C locale and fixes what is effectively a regression in
musl's property of always providing working UTF-8 support.
commit 1507ebf837334e9e07cfab1ca1c2e88449069a80 introduced the codeset
name "UTF-8-CODE-UNITS" for the byte-based C locale to represent that
the semantic content is UTF-8 but that it is being processed as code
units (bytes) rather than whole multibyte characters. however, many
programs assume that the codeset name is usable with iconv and/or
comes from a set of standard/widely-used names known to the
application. such programs are likely to produce warnings or errors,
run with reduced functionality, or mangle character data when run
explicitly in the C locale.
the standard places basically no requirements for the string returned
by nl_langinfo(CODESET) and how it interacts with other interfaces, so
returning "UTF-8" is permissible. moreover, it seems like the right
thing to do, since the identity of the character encoding as "UTF-8"
is independent of whether it is being processed as bytes of characters
by the standard library functions.
this fixes a bug reported by Nuno Gonçalves. previously, calling
fclose on stdin or stdout resulted in deadlock at exit time, since
__stdio_exit attempts to lock these streams to flush/seek them, and
has no easy way of knowing that they were closed.
conceptually, leaving a FILE stream locked on fclose is valid since,
in the abstract machine, it ceases to exist. but to satisfy the
implementation-internal assumption in __stdio_exit that it can access
these streams unconditionally, we need to unlock them.
it's also necessary that fclose leaves permanent streams in a state
where __stdio_exit will not attempt any further operations on them.
fortunately, the call to fflush already yields this property.
Timo Teräs [Sun, 30 Aug 2015 15:58:26 +0000 (18:58 +0300)]
implement arm eabi mem* functions
these functions are part of the ARM EABI, meaning compilers may
generate references to them. known versions of gcc do not use them,
but llvm does. they are not provided by libgcc, and the de facto
standard seems to be that libc provides them.
Rich Felker [Sun, 30 Aug 2015 18:44:58 +0000 (18:44 +0000)]
remove use of buggy .SECONDARY special target in makefile
this functionality is affected by GNU make bug #30653, "intermediate
files incorrectly pruned in parallel builds". on affected versions of
make, parallel builds attempt to compile source files before
alltypes.h is generated.
as noted with commit a91ebdcfac6804714a1fe39f4375e2b4ebab085b, which
added the use of .SECONDARY, suppression of removal of "intermediate"
files does not seem to be needed at present. if it is needed in the
future, it should be achievable by explicitly mentioning their names
as targets or prerequisites.
Rich Felker [Thu, 27 Aug 2015 19:58:20 +0000 (19:58 +0000)]
fix makefile suppression of intermediate file removal
at one point, GNU make was removing crt/*.o after producing the copies
in lib/ due to an arcane misfeature for handling "intermediate" files.
the circumstances that caused this are no longer present in our
makefile, but the previous workaround using .PRECIOUS was wrong and
could result in corrupt/partial files being left behind during an
interrupted build. using .SECONDARY is the correct, documented fix
that will prevent deletion of "intermediate" files from ever
resurfacing.
Alex Dowad [Fri, 10 Jul 2015 13:03:24 +0000 (15:03 +0200)]
Build process uses script to add CFI directives to x86 asm
Some functions implemented in asm need to use EBP for purposes other
than acting as a frame pointer. (Notably, it is used for the 6th
argument to syscalls with 6 arguments.) Without frame pointers, GDB
can only show backtraces if it gets CFI information from a
.debug_frame or .eh_frame ELF section.
Rather than littering our asm with ugly .cfi directives, use an awk
script to insert them in the right places during the build process, so
GDB can keep track of where the current stack frame is relative to the
stack pointer. This means GDB can produce beautiful stack traces at
any given point when single-stepping through asm functions.
Additionally, when registers are saved on the stack and later
overwritten, emit ..cfi directives so GDB will know where they were
saved relative to the stack pointer. This way, when you look back up
the stack from within an asm function, you can still reliably print
the values of local variables in the caller.
If this awk script were to understand every possible wild and crazy
contortion that an asm programmer can do with the stack and registers,
and always emit the exact ..cfi directives needed for GDB to know what
the register values were in the preceding stack frame, it would
necessarily be as complex as a full x86 emulator. That way lies
madness.
Hence, we assume that the stack pointer will _only_ ever be adjusted
using push/pop or else add/sub with a constant. We do not attempt to
detect every possible way that a register value could be saved for
later use, just the simple and common ways.
Thanks to Szabolcs Nagy for suggesting numerous improvements to this
code.
Rich Felker [Sun, 16 Aug 2015 18:15:18 +0000 (18:15 +0000)]
mitigate performance regression in libc-internal locks on x86_64
commit 3c43c0761e1725fd5f89a9c028cbf43250abb913 fixed missing
synchronization in the atomic store operation for i386 and x86_64, but
opted to use mfence for the barrier on x86_64 where it's always
available. however, in practice mfence is significantly slower than
the barrier approach used on i386 (a nop-like lock orl operation).
this commit changes x86_64 (and x32) to use the faster barrier.
Natanael Copa [Thu, 13 Aug 2015 15:28:39 +0000 (17:28 +0200)]
match historical behavior for tm_gmtoff member of struct tm
tm_gmtoff is a nonstandard field, but on historical systems which have
this field, it stores the offset of the local time zone from GMT or
UTC. this is the opposite of the POSIX extern long timezone object and
the offsets used in POSIX-form TZ strings, which represent the offset
from local time to UTC. previously we were storing these negated
offsets in tm_gmtoff too.
programs which only used this field indirectly via strftime were not
affected since strftime performed the negation for presentation.
however, some programs and libraries accesse tm_gmtoff directly and
were obtaining negated time zone offsets.
Szabolcs Nagy [Tue, 11 Aug 2015 20:55:18 +0000 (20:55 +0000)]
aarch64: fix 64-bit syscall argument passing
On 32bit systems long long arguments are passed in a special way
to some syscalls; this accidentally got copied to the AArch64 port.
The following interfaces were broken: fallocate, fanotify, ftruncate,
posix_fadvise, posix_fallocate, pread, pwrite, readahead,
sync_file_range, truncate.
Rich Felker [Fri, 7 Aug 2015 19:19:49 +0000 (19:19 +0000)]
mitigate blow-up of heap size under malloc/free contention
during calls to free, any free chunks adjacent to the chunk being
freed are momentarily held in allocated state for the purpose of
merging, possibly leaving little or no available free memory for other
threads to allocate. under this condition, other threads will attempt
to expand the heap rather than waiting to use memory that will soon be
available. the race window where this happens is normally very small,
but became huge when free chooses to use madvise to release unused
physical memory, causing unbounded heap size growth.
this patch drastically shrinks the race window for unwanted heap
expansion by performing madvise with the bin lock held and marking the
bin non-empty in the binmask before making the expensive madvise
syscall. testing by Timo Teräs has shown this approach to be a
suitable mitigation.
more invasive changes to the synchronization between malloc and free
would be needed to completely eliminate the problem. it's not clear
whether such changes would improve or worsen typical-case performance,
or whether this would be a worthwhile direction to take malloc
development.
fix missing synchronization in atomic store on i386 and x86_64
despite being strongly ordered, the x86 memory model does not preclude
reordering of loads across earlier stores. while a plain store
suffices as a release barrier, we actually need a full barrier, since
users of a_store subsequently load a waiter count to determine whether
to issue a futex wait, and using a stale count will result in soft
(fail-to-wake) deadlocks. these deadlocks were observed in malloc and
possible with stdio locks and other libc-internal locking.
on i386, an atomic operation on the caller's stack is used as the
barrier rather than performing the store itself using xchg; this
avoids the need to read the cache line on which the store is being
performed. mfence is used on x86_64 where it's always available, and
could be used on i386 with the appropriate cpu model checks if it's
shown to perform better.
fix atexit when it is called from an atexit handler
The old code accepted atexit handlers after exit, but did not run them
reliably. C11 seems to explicitly allow atexit to fail (and report
such failure) in this case, but this situation can easily come up in
C++ if a destructor has a local static object with a destructor so it
should be handled.
Note that the memory usage can grow linearly with the overall number
of registered atexit handlers instead of with the worst case list
length. (This only matters if atexit handlers keep registering atexit
handlers which should not happen in practice).
Commit message/rationale based on text by Szabolcs Nagy.
when traditional syslogd implementations are restarted, the old server
socket ceases to exist and a new unix socket with the same pathname is
created. when this happens, the default destination address associated
with the client socket via connect is no longer valid, and attempts to
send produce errors. this happens despite the socket being datagram
type, and is in contrast to the behavior that would be seen with an IP
datagram (UDP) socket.
in order to avoid a situation where the application is unable to send
further syslog messages without calling closelog, this patch makes
syslog attempt to reconnect the socket when send returns an error
indicating a lost connection.
additionally, initial failure to connect the socket no longer results
in the socket being closed. this ensures that an application which
calls openlog to reserve the socket file descriptor will not run into
a situation where transient connection failure (e.g. due to syslogd
restart) prevents fd reservation. however, applications which may be
unable to connect the socket later (e.g. due to chroot, restricted
permissions, seccomp, etc.) will still fail to log if the syslog
socket cannot be connected at openlog time or if it has to be
reconnected later.
fix incorrect void return type for syncfs function
being nonstandard, the closest thing to a specification for this
function is its man page, which documents it as returning int. it can
fail with EBADF if the file descriptor passed is invalid.
Shiz [Sun, 28 Jun 2015 21:08:21 +0000 (23:08 +0200)]
add musl-clang, a wrapper for system clang installs
musl-clang allows the user to compile musl-powered programs using their
already existent clang install, without the need of a special cross compiler.
it achieves this by wrapping around both the system clang install and the
linker and passing them special flags to re-target musl at runtime.
it does only affect invocations done through the special musl-clang wrapper
script, so that the user setup remains fully intact otherwise.
the clang wrapper consists of the compiler frontend wrapper script,
musl-clang, and the linker wrapper script, ld.musl-clang.
musl-clang makes sure clang invokes ld.musl-clang to link objects; neither
script needs to be in PATH for the wrapper to work.
Shiz [Sun, 28 Jun 2015 21:08:20 +0000 (23:08 +0200)]
build: fix musl-targeting toolchain test
the old test was broken in that it would never fail on a toolchains built
without dynamic linking support, leading to the wrapper script possibly being
installed on compilers that do not support it. in addition, the new test is
portable across compilers: the old test only worked on GCC.
the new test works by testing whether the toolchain libc defines __GLIBC__:
most non-musl Linux libc's do define this for compatibility even when they
are not glibc, so this is a safe bet to check for musl. in addition, the
compiler runtime would need to have a somewhat glibc-compatible ABI in the
first place, so any non-glibc compatible libc's compiler runtime might not
work. it is safer to disable these cases by default and have the user enable
the wrappers manually there using --enable-wrapper if they certain it works.
Shiz [Sun, 28 Jun 2015 21:08:19 +0000 (23:08 +0200)]
build: overhaul wrapper script system for multiple wrapper support
this overhauls part of the build system in order to support multiple
toolchain wrapper scripts, as opposed to solely the musl-gcc wrapper as
before. it thereby replaces --enable-gcc-wrapper with --enable-wrapper=...,
which has the options 'auto' (the default, detect whether to use wrappers),
'all' (build and install all wrappers), 'no' (don't build any) and finally
the options named after the individual compiler scripts (currently only
'gcc' is available) to build and install only that wrapper.
the old --enable-gcc-wrapper is removed from --help, but still available.
it also modifies the wrappers to use the C compiler specified to the build
system as 'inner' compiler, when applicable. as wrapper detection works by
probing this compiler, it may not work with any other.
treat empty TZ environment variable as GMT rather than default
this improves compatibility with the behavior of other systems and
with some applications which set an empty TZ var to disable use of
local time by mktime, etc.
dynlink.c: pass gnu-hash table pointer to gnu_lookup
The callers need to check the value of the pointer anyway, so make
them pass the pointer to gnu_lookup instead of reloading it there.
Reorder gnu_lookup arguments so that always-used ones are listed
first. GCC can choose a calling convention with arguments in registers
(e.g. up to 3 arguments in eax, ecx, edx on x86), but cannot reorder
the arguments for static functions.
Introduce gnu_lookup_filtered and use it to speed up symbol lookups in
find_sym (do_dlsym is left as is, based on an expectation that
frequently dlsym queries will use a dlopen handle rather than
RTLD_NEXT or RTLD_DEFAULT, and will not need to look at more than one
DSO).
Rich Felker [Thu, 25 Jun 2015 22:22:00 +0000 (22:22 +0000)]
fix local-dynamic model TLS on mips and powerpc
the TLS ABI spec for mips, powerpc, and some other (presently
unsupported) RISC archs has the return value of __tls_get_addr offset
by +0x8000 and the result of DTPOFF relocations offset by -0x8000. I
had previously assumed this part of the ABI was actually just an
implementation detail, since the adjustments cancel out. however, when
the local dynamic model is used for accessing TLS that's known to be
in the same DSO, either of the following may happen:
1. the -0x8000 offset may already be applied to the argument structure
passed to __tls_get_addr at ld time, without any opportunity for
runtime relocations.
2. __tls_get_addr may be used with a zero offset argument to obtain a
base address for the module's TLS, to which the caller then applies
immediate offsets for individual objects accessed using the local
dynamic model. since the immediate offsets have the -0x8000 adjustment
applied to them, the base address they use needs to include the
+0x8000 offset.
it would be possible, but more complex, to store the pointers in the
dtv[] array with the +0x8000 offset pre-applied, to avoid the runtime
cost of adding 0x8000 on each call to __tls_get_addr. this change
could be made later if measurements show that it would help.
Rich Felker [Tue, 23 Jun 2015 04:03:42 +0000 (04:03 +0000)]
make dynamic linker work around MAP_FAILED mmap failure on nommu kernels
previously, loading of additional libraries beyond libc/ldso did not
work on nommu kernels, nor did loading programs via invocation of the
dynamic linker as a command.
Rich Felker [Tue, 23 Jun 2015 00:12:25 +0000 (00:12 +0000)]
reimplement strverscmp to fix corner cases
this interface is non-standardized and is a GNU invention, and as
such, our implementation should match the behavior of the GNU
function. one peculiarity the old implementation got wrong was the
handling of all-zero digit sequences: they are supposed to compare
greater than digit sequences of which they are a proper prefix, as in
009 < 00.
in addition, high bytes were treated with char signedness rather than
as unsigned. this was wrong regardless of what the GNU function does
since the resulting order relation varied by arch.
the new strverscmp implementation makes explicit the cases where the
order differs from what strcmp would produce, of which there are only
two.
Rich Felker [Mon, 22 Jun 2015 20:33:28 +0000 (20:33 +0000)]
fix regression/typo that disabled __simple_malloc when calloc is used
commit ba819787ee93ceae94efd274f7849e317c1bff58 introduced this
regression. since the __malloc0 weak alias was not properly provided
by __simple_malloc, use of calloc forced the full malloc to be linked.
Rich Felker [Mon, 22 Jun 2015 18:50:09 +0000 (18:50 +0000)]
fix calloc when __simple_malloc implementation is used
previously, calloc's implementation encoded assumptions about the
implementation of malloc, accessing a size_t word just prior to the
allocated memory to determine if it was obtained by mmap to optimize
out the zero-filling. when __simple_malloc is used (static linking a
program with no realloc/free), it doesn't matter if the result of this
check is wrong, since all allocations are zero-initialized anyway. but
the access could be invalid if it crosses a page boundary or if the
pointer is not sufficiently aligned, which can happen for very small
allocations.
this patch fixes the issue by moving the zero-fill logic into malloc.c
with the full malloc, as a new function named __malloc0, which is
provided by a weak alias to __simple_malloc (which always gives
zero-filled memory) when the full malloc is not in use.
Rich Felker [Sat, 20 Jun 2015 03:01:07 +0000 (03:01 +0000)]
provide __stack_chk_fail_local in libc.a
this symbol is needed only on archs where the PLT call ABI is klunky,
and only for position-independent code compiled with stack protector.
thus references usually only appear in shared libraries or PIE
executables, but they can also appear when linking statically if some
of the object files being linked were built as PIC/PIE.
normally libssp_nonshared.a from the compiler toolchain should provide
__stack_chk_fail_local, but reportedly it appears prior to -lc in the
link order, thus failing to satisfy references from libc itself (which
arise only if libc.a was built as PIC/PIE with stack protector
enabled).
Rich Felker [Sat, 20 Jun 2015 02:54:30 +0000 (02:54 +0000)]
work around mips detached thread exit breakage due to kernel regression
linux kernel commit 46e12c07b3b9603c60fc1d421ff18618241cb081 caused
the mips syscall mechanism to fail with EFAULT when the userspace
stack pointer is invalid, breaking __unmapself used for detached
thread exit. the workaround is to set $sp to a known-valid, readable
address, and the simplest one to obtain is the address of the current
function, which is available (per o32 calling convention) in $25.
projects / musl / log