this commit preserves ABI fully for existing interface boundaries
between libc and libc consumers (applications or libraries), by
retaining existing symbol names for the legacy 32-bit interfaces and
redirecting sources compiled against the new headers to alternate
symbol names. this does not necessarily, however, preserve the
pairwise ABI of libc consumers with one another; where they use
time_t-derived types in their interfaces with one another, it may be
necessary to synchronize updates with each other.
the intent is that ABI resulting from this commit already be stable
and permanent, but it will not be officially so until a release is
made. changes to some header-defined types that do not play any role
in the ABI between libc and its consumers may still be subject to
change.
mechanically, the changes made by this commit for each 32-bit arch are
as follows:
- _REDIR_TIME64 is defined to activate the symbol redirections in
public headers
- COMPAT_SRC_DIRS is defined in arch.mak to activate build of ABI
compat shims to serve as definitions for the original symbol names
- time_t and suseconds_t definitions are changed to long long (64-bit)
- IPC_STAT definition is changed to add the IPC_TIME64 bit (0x100),
triggering conversion of semid_ds, shmid_ds, and msqid_ds split
low/high time bits into new time_t members
- structs semid_ds, shmid_ds, msqid_ds, and stat are modified to add
new 64-bit time_t/timespec members at the end, maintaining existing
layout of other members.
- socket options (SO_*) and ioctl (sockios) command macros are
redefined to use the kernel's "_NEW" values.
in addition, on archs where vdso clock_gettime is used, the
VDSO_CGT_SYM macro definition in syscall_arch.h is changed to use a
new time64 vdso function if available, and a new VDSO_CGT32_SYM macro
is added for use as fallback on kernels lacking time64.
these definitions are copied from generic bits/ioctl.h, so that x32
keeps the "_OLD" versions (which are already time64 on x32) when
32-bit archs switch to 64-bit time_t.
these definitions are merely copied from the top-level sys/socket.h,
so there is no functional change at this time. however, the top-level
definitions will change to use the time64 "_NEW" versions on 32-bit
archs when time_t is switched over to 64-bit. this commit ensures that
change will be suppressed on x32.
these structures can now be defined generically in terms of endianness
and long size. previously, the 32-bit archs all shared a common
definition from the generic bits header, and each 64-bit arch had to
repeat the 64-bit version, with endian conditionals if the arch had
variants of each endianness.
I would prefer getting rid of the preprocessor conditionals for
padding and instead using unnamed bitfield members, like commit
9b2921bea1 did for struct timespec.
however, at present sendmsg, recvmsg, and recvmmsg need access to the
padding members by name to zero them. this could perhaps be cleaned up
in the future.
being that it contains pointers and (from the kernel perspective,
which is wrong) size_t members, x32 uses the 32-bit version of the
structure, not a half-32-bit, half-64-bit layout like we had here. the
x86_64 definition was inadvertently copied when x32 was first added.
unlike errors in the opposite direction (missing padding), this error
was not easily detected breakage, because the layout of the commonly
used initial subset of members still matched. breakage could only be
observed in the presence of control messages or flags.
SO_RCVTIMEO and SO_SNDTIMEO already were, but only in aggregate with
SO_DEBUG and all of the other low/traditional options that varied per
arch. SO_TIMESTAMP* are newly overridable. the two groups have to be
done separately since mips64 and powerpc64 will override the former
but not the latter.
at some point this should be cleaned up to use bits headers more
idiomatically.
the immediate usage case for this is to let 32-bit archs moving to
64-bit time_t via symbol redirection pull in wrapper shims that
provide the old symbol names. in the future it may be used for other
types of compatibility-only source files that are not relevant to all
archs.
if symbols are being redirected to provide the new time64 ABI, dlsym
must perform matching redirections; otherwise, it would poke a hole in
the magic and return pointers to functions that are not safe to call
from a caller using time64 types.
rather than duplicating a table of redirections, use the time64
symbols present in libc's symbol table to derive the decision for
whether a particular symbol needs to be redirected.
these files provide the symbols for the traditional 32-bit time_t ABI
on existing 32-bit archs by wrapping the real, internal versions of
the corresponding functions, which always work with 64-bit time_t.
they are written to be as agnostic as possible to the implementation
details of the real functions, so that they can be written once and
mostly forgotten, but they are aware of details of the old (and
sometimes new) ABI, which is okay since ABI is fixed and cannot
change.
a new compat tree is added, separate from src, which the Makefile does
not see or use now, but which archs will be able to add to the build
process. we could also consider moving other things that are compat
shims here, like functions which are purely for glibc-ABI-compat, with
the goal of making it optional or just cleaning up the main src tree
to make the distinction between actual implementation/API files and
ABI-compat shims clear.
here _REDIR_TIME64 is used as an indication that there's an old ABI,
and thereby the old time32 timespec fields of struct stat.
keeping struct stat compatible and providing both versions of the
timespec fields is done so that ftw/nftw does not need painful compat
shims, and (more importantly) so that similar interfaces between pairs
of libc consumers (applications/libraries) will be less likely to
break when one has been rebuilt for time64 but the other has not.
these functions cannot provide the glibc lfs64-ABI-compatible symbols
when time_t differs from what it was in that ABI. instead, the aliases
need to be provided by the time32 compat shims or through some other
mechanism.
the time_t members in struct sched_param are just reserved space to
preserve size and alignment. when time_t changes to 64-bit on 32-bit
archs, this structure should not change.
make definition conditional on _REDIR_TIME64 to match the size of the
old time_t, which can be assumed to be long if _REDIR_TIME64 is
defined.
a _REDIR_TIME64 macro is introduced, which the arch's alltypes.h is
expected to define, to control redirection of symbol names for
interfaces that involve time_t and derived types. this ensures that
object files will only be linked to libc interfaces matching the ABI
whose headers they were compiled against.
along with time32 compat shims, which will be introduced separately,
the redirection also makes it possible for a single libc (static or
shared) to be used with object files produced with either the old
(32-bit time_t) headers or the new ones after 64-bit time_t switchover
takes place. mixing of such object files (or shared libraries) in the
same program will also be possible, but must be done with care; ABI
between libc and a consumer of the libc interfaces is guaranteed to
match by the the symbol name redirection, but pairwise ABI between
consumers of libc that define interfaces between each other in terms
of time_t is not guaranteed to match.
this change adds a dependency on an additional "GNU C" feature to the
public headers for existing 32-bit archs, which is generally
undesirable; however, the feature is one which glibc has depended on
for a long time, and thus which any viable alternative compiler is
going to need to provide. 64-bit archs are not affected, nor will
future 32-bit archs be, regardless of whether they are "new" on the
kernel side (e.g. riscv32) or just newly-added (e.g. a new sparc or
xtensa port). the same applies to newly-added ABIs for existing
machine-level archs.
the existing implementation of case mappings was very small (typically
around 1.5k), but unmaintainable, requiring manual addition of new
case mappings with each new edition of Unicode. often, it turned out
that newly-added case mappings were not easily representable in the
existing tightly-constrained table structures, requiring new hacks to
be invented and delaying support for new characters.
the new implementation added here follows the pattern used for
character class membership, with a two-level table allowing Unicode
blocks for which no data is needed to be elided. however, rather than
single-bit data, each character maps to a one of up to 6 case-mapping
rules available to its block, where 6 is floor(cbrt(256)) and allow 3
characters to be represented per byte (vs 8 with bit tables). blocks
that would need more than 6 rules designate one as an exception and
let lookup pass into a binary search of exceptional cases for the
block.
the number 6 was chosen empirically; many blocks would be ok with 4
rules (uncased, lower, upper, possible exceptions), some even just
with 2, but the latter are rare and fitting 4 characters per byte
rather than 3 does not save significant space. moreover, somewhat
surprisingly, there are sufficiently many blocks where even 4 rules
don't suffice without a lot of exceptions (blocks where some case
pairs are laced, others offset) that originally I was looking at
supporting variable-width tables, with 1-, 2-, or 3-bit entries,
thereby allowing blocks with 8 rules. as implemented in my
experiments, that version was significantly larger and involved more
memory accesses/cache lines.
improvements in size at the expense of some performance might be
possible by utilizing iswalpha data or merging the table of case
mapping identity with alphabetic identity. these were explored
somewhat when the code was first written, and might be worth
revisiting in the future.
somehow this seems to have been overlooked. add it now so that
subsequent overhaul of case mapping implementation will not introduce
a functional change at the same time.
for time64 support on 32-bit archs, the kernel interfaces use a
timespec layout padded to match the representation of a pair of 64-bit
values, which requires endian-specific padding.
use of an ordinary, non-bitfield, named member for the padding is
undesirable because, on big endian archs, it would alter the
interpretation of traditional (non-designated) initializers of the
form {s,ns}, initializing the padding instead of the tv_nsec member.
unnamed bitfield members solve this problem by not taking part in
initialization, and were the expected solution when the kernel
interfaces were designed. however, they also have further advantages
which we take advantage of here:
positioning of the padding could be controlled by having a
preprocessor conditional with separate definitions of struct timespec
for little and big endian, but whether padding should appear at all is
a function of whether time_t is larger than long. this condition is
not something the preprocessor can determine unless we were to define
a new macro specifically for that purpose.
by using unnamed bitfield members instead of ordinary named members,
we can arrange for the size of the padding to collapse to zero when it
should not be present, just by using sizeof(time_t) and sizeof(long)
in the bitfield width expression, which can be any integer constant
expression.
commit 2b4fd6f75b added time64 for this
function, but did so with a hidden assumption that the new time64
version of struct timex will be layout-compatible with the old one.
however, there is little benefit to doing it that way, and the cost is
permanent special-casing of 32-bit archs with 64-bit time_t in the
public interface definitions.
instead, do a full translation of the structure going in and out. this
commit is actually a revision to an earlier uncommited version of the
code.
presently the kernel does not actually define time64 versions of these
syscalls, and they're not really needed except to represent extreme
cpu time usage. however, x32's versions of the syscalls already behave
as time64 ones, meaning the functions were broken on x32 if the caller
used any part of the rusage result other than ru_utime and ru_stime.
commit 7e81711431 made it possible to
fix this by treating x32's syscalls as time64 versions.
in the non-time64-syscall case, make the syscall with the rusage
destination pointer adjusted so that all members but the timevals line
up between the libc and kernel structures. on 64-bit archs, or present
32-bit archs with 32-bit time_t, the timevals will line up too and no
further work is needed. for future 32-bit archs with 64-bit time_t,
the timevals are copied into place, contingent on time_t being larger
than long.
this is analogous to commit 40aa18d55a.
so far, there are not any actual time64 versions of the rusage
syscalls (getrusage and wait4) and might never be. however, the
existing x32 ones behave the way time64 versions would if they
existed: using 64-bit slots in place of all longs.
presently, wait4 and getrusage are broken on x32, storing the timevals
correctly but messing up everything else due to the long/kernel-long
mismatch. this would be a huge buffer overflow if not for the 16
reserved slots we left long ago, which suffice to prevent 14
double-sized longs from overflowing into unrelated memory. this commit
will make it possible to fix them.
this is to match the kernel and glibc interfaces. here, struct pt_regs
is an incomplete type, but that's harmless, and if it's completed by
inclusion of another header then members of the struct pointed to by
the regs member can be accessed directly without going through a cast
or intermediate pointer object.
the userspace ucontext API has this as an array rather than a
structure.
commit 3c59a86895 fixed the
corresponding mistake for vrregset_t, namely that the original
powerpc64 port used a mix of types from 32-bit powerpc and powerpc64
rather than matching the 64-bit types.
aside from the special value EOF, ungetc is specified to accept and
convert values outside the range of unsigned char. conversion takes
place automatically as part of assignment when storing into the
buffer, but the return value is also required to be the resulting
converted value, and this requirement was not satisfied.
simplified from patch by Wang Jianjian.
based on patch by Dan Gohman, who caught this via compiler warnings.
analysis by Szabolcs Nagy determined that it's a bug, whereby errno
can be set incorrectly for values where the coercion from long double
to double causes rounding. it seems likely that floating point status
flags may be set incorrectly as a result too.
at the same time, clean up use of preprocessor concatenation involving
LDBL_MANT_DIG, which spuriously depends on it being a single unadorned
decimal integer literal, and instead use the equivalent formulation
2/LDBL_EPSILON. an equivalent change on the printf side was made in
commit bff6095d91.
policy has long been that these definitions are purely a function of
whether long/pointer is 32- or 64-bit, and that they are not allowed
to vary per-arch. move the definition to the shared alltypes.h.in
fragment, using integer constant expressions in terms of sizeof to
vary the array dimensions appropriately. I'm not sure whether this is
more or less ugly than using preprocessor conditionals and two sets of
definitions here, but either way is a lot less ugly than repeating the
same thing for every arch.
LLONG_MAX is uniform for all archs we support and plenty of header and
code level logic assumes it is, so it does not make sense for limits.h
bits mechanism to pretend it's variable.
LONG_BIT can be defined in terms of LONG_MAX; there's no reason to put
it in bits.
by moving LONG_MAX definition to __LONG_MAX in alltypes.h and moving
LLONG_MAX out of bits, there are now no plain-C limits that are
defined in the bits header, so the bits header only needs to be
included in the POSIX or extended profiles. this allows the feature
test macro logic to be removed from the bits header, facilitating a
long-term goal of getting such logic out of bits.
having __LONG_MAX in alltypes.h will allow further generalization of
headers.
archs without a constant PAGESIZE no longer need bits/limits.h at all.
the resolution of Austin Group issue #162 adds endian.h as a standard
header for future versions of the standard, making it no longer
acceptable for some of the functionality to be hidden behind
_BSD_SOURCE or _GNU_SOURCE. the definitions of the [lb]etoh{16,32,64}
function-like macros are kept conditional since they are alternate
names which the standard did not adopt.
building on commit 97d35a552e,
__BYTE_ORDER is now available wherever alltypes.h is included. since
reloc.h is only used from src/internal/dynlink.h, it can be assumed
that __BYTE_ORDER is exposed. reloc.h is not permitted to be included
in other contexts, and generally, like most arch headers, lacks
inclusion guards that would allow such usage. the mips64 version
mistakenly included such guards; they are removed for consistency.
building on commit 97d35a552e,
__BYTE_ORDER is now available wherever alltypes.h is included.
endian.h should not be used since, in the future, it will expose
identifiers that are not in the reserved namespace for the headers
which were previously using it.
this change is motivated by the intersection of several factors.
presently, despite being a nonstandard header, endian.h is exposing
the unprefixed byte order macros and functions only if _BSD_SOURCE or
_GNU_SOURCE is defined. this is to accommodate use of endian.h from
other headers, including bits headers, which need to define structure
layout in terms of endianness. with time64 switch-over, even more
headers will need to do this.
at the same time, the resolution of Austin Group issue 162 makes
endian.h a standard header for POSIX-future, requiring that it expose
the unprefixed macros and the functions even in standards-conforming
profiles. changes to meet this new requirement would break existing
internal usage of endian.h by causing it to violate namespace where
it's used.
instead, have the arch's alltypes.h define __BYTE_ORDER, either as a
fixed constant or depending on the right arch-specific predefined
macros for determining endianness. explicit literals 1234 and 4321 are
used instead of __LITTLE_ENDIAN and __BIG_ENDIAN so that there's no
danger of getting the wrong result if a macro is undefined and
implicitly evaluates to 0 at the preprocessor level.
the powerpc (32-bit) bits/endian.h being removed had logic for varying
endianness, but our powerpc arch has never supported that and has
always been big-endian-only. this logic is not carried over to the new
__BYTE_ORDER definition in alltypes.h.
now that commit f7f1079796 removed the
legacy i386 conditional definition, va_list is in no way
arch-specific, and has no reason to be in the future. move it to the
shared part of alltypes.h.in
commit ffaaa6d230 removed the
corresponding stdarg.h support for compilers without va_list builtins,
but failed to remove the alternate type definition, leaving incorrect
va_list definitions in place with compilers that don't define __GNUC__
with a value >= 3.
SQRT.fmt exists on MIPS II+ (float), MIPS III+ (double).
ABS.fmt exists on MIPS I+ but only cores with ABS2008 flag in FCSR
implement the required behaviour.
Both sqrt and sqrtf shifted the signed exponent as signed int to adjust
the bit representation of the result. There are signed right shifts too
in the code but those are implementation defined and are expected to
compile to arithmetic shift on supported compilers and targets.
mbsrtowcs contains "vectorized" loops to quickly step over bytes
without the high bit set; these have undefined behavior by virtue of
aliasing uint32_t over top of char data for the accesses.
commit 4d0a82170a fixed the
corresponding usage in string functions by using the may_alias
attribute conditional on __GNUC__ and disabled the vectorized code in
its absence. do the same for mbsrtowcs.
Several math functions are now from the ARM optimized-routines repo
licensed under standard MIT terms and copyrighted by Arm Limited,
so mention this in the COPYRIGHT too.
commit ab3eb89a8b removed it as part of
correcting the mcontext_t definition, but there is still code using
struct sigcontext and expecting the member names present in it, most
notably libgcc_eh. almost all such usage is incorrect, but bring back
struct sigcontext at least for now so as not to introduce regressions.
in order for sys/procfs.h (provided by sys/user.h) to be useful, it
needs to match the API its consumers (gdb, etc.) expect, including the
member names established by glibc.
this partly reverts commit 29e8737f81,
which partly reverted d493206de7,
eliminating struct user_fpregs_struct which seems to have had no
precedent and using union __riscv_mc_fp_state for elf_fpregset_t. this
requires indirect inclusion of signal.h to make union
__riscv_mc_fp_state visible, but being that these are nonstandard
"junk" headers with no official restrictions on what they can pull in,
that's no big deal.
split off and expanded from patch by Khem Raj.
the top-level mcontext_t member names were namespace-violating in
standards profiles before, and nested-level member names (some of them
single-letter) were egregiously bad namespace impositions even in
non-strict profiles. moreover, they mismatched those used in the
public API first defined in glibc, breaking any code making use of
them.
unlike most archs, the public API used in glibc for riscv mcontext_t
members was designed to be namespace-safe, so we can and should expose
the members regardless of feature test macros. only the typedefs for
greg_t, gregset_t, and fpregset_t need to be protected behind FTMs.
the struct tags for mcontext_t and ucontext_t are also changed. for
mcontext_t this is necessary to make the common definition across
profiles namespace-safe. for ucontext_t, it's just a matter of
matching the tag from the glibc-defined API.
these changes are split off and expanded from a patch by Khem Raj.
Some declarations of __tls_get_new were left in the code, even
though the definition got removed in
commit 9d44b6460a
install dynamic tls synchronously at dlopen, streamline access
this can make the build fail with
ld: lib/libc.so: hidden symbol `__tls_get_new' isn't defined
when libc.so is linked without --gc-sections, because a .hidden
declaration in asm code creates a reference even if the symbol
is not actually used.
lrint in (LONG_MAX, 1/DBL_EPSILON) and in (-1/DBL_EPSILON, LONG_MIN)
is not trivial: rounding to int may be inexact, but the conversion to
int may overflow and then the inexact flag must not be raised. (the
overflow threshold is rounding mode dependent).
this matters on 32bit targets (without single instruction lrint or
rint), so the common case (when there is no overflow) is optimized by
inlining the lrint logic, otherwise the old code is kept as a fallback.
on my laptop an i486 lrint call is asm:10ns, old c:30ns, new c:21ns
on a smaller arm core: old c:71ns, new c:34ns
on a bigger arm core: old c:27ns, new c:19ns
analogous to commit ddc7c4f936 for
mips64 and n32, remove the hack to load the syscall number into $2 via
asm, and use a constraint to let the compiler load it instead.
now, only $4, $5, and $6 are potential input-only registers. $2 is
always input and output, and $7 is both when it's an argument,
otherwise output-only. previously, $7 was treated as an input (with a
"1" constraint matching its output position) even when it was not an
input, which was arguably undefined behavior (asm input from
indeterminate value). this is corrected.
as before, $8, $9, and $10 are conditionally input-output registers
for 5-, 6-, and 7-argument syscalls. their role in input is carrying
in the values that will be stored on the stack for arguments 5-7.
their role in output is carrying back whatever the kernel has
clobbered them with, so that the compiler cannot assume they still
contain the input values.
mips32 has two fpu register file variants: FR=0 with 32 32-bit
registers, where pairs of neighboring even/odd registers are used to
represent doubles, and FR=1 with 32 64-bit registers, each of which
can store a single or double.
up through r5 (our "mips" arch), the supported ABI uses FR=0, but
modern compilers generate "fpxx" model code that can safely operate
with either model. r6, which is an incompatible but similar ISA, drops
FR=0 and only provides the FR=1 model. as such, setjmp and longjmp,
which depended on being able to save and restore call-saved doubles by
storing and loading their 32-bit halves, were completely broken in the
presence of floating point code on mips r6.
to fix this, use the s.d and l.d mnemonics to store and load fpu
registers. these expand to the existing swc1 and lwc1 instructions for
pairs of 32-bit fpu registers on mips1, but on mips2 and later they
translate directly to the 64-bit sdc1 and ldc1.
with FR=0, sdc1 and ldc1 behave just like the pairs of swc1 and lwc1
instructions they replace, storing or loading the even/odd pair of fpu
registers that can be treated as separate single-precision floats or
as a unit representing a double. but with FR=1, they store/load
individual 64-bit registers. this yields the ABI-correct behavior on
mips r6, and should make linking of pre-r6 (plain "mips") code with
"fp64" model code workable, although this is and will likely remain
unsupported usage.
in addition to the mips r6 problem this change fixes, reportedly
clang's internal assembler refuses to assemble swc1 and lwc1
instructions for odd register indices when building for "fpxx" model
(the default). this caused setjmp and longjmp not to build. by using
the s.d and l.d forms, this problem is avoided too.
as a bonus, code size is reduced everywhere but mips1.
Rich Felker
u_quark
info@mobile-stream.com
Michael Morrell
Szabolcs Nagy