In TLS variant I the TLS is above TP (or above a fixed offset from TP)
but on some targets there is a reserved gap above TP before TLS starts.
This matters for the local-exec tls access model when the offsets of
TLS variables from the TP are hard coded by the linker into the
executable, so the libc must compute these offsets the same way as the
linker. The tls offset of the main module has to be
alignup(GAP_ABOVE_TP, main_tls_align).
If there is no TLS in the main module then the gap can be ignored
since musl does not use it and the tls access models of shared
libraries are not affected.
The previous setup only worked if (tls_align & -GAP_ABOVE_TP) == 0
(i.e. TLS did not require large alignment) because the gap was
treated as a fixed offset from TP. Now the TP points at the end
of the pthread struct (which is aligned) and there is a gap above
it (which may also need alignment).
The fix required changing TP_ADJ and __pthread_self on affected
targets (aarch64, arm and sh) and in the tlsdesc asm the offset to
access the dtv changed too.
the output delay features (NL*, CR*, TAB*, BS*, and VT*) are
XSI-shaded. VT* is in the V* namespace reservation but the rest need
to be suppressed in base POSIX namespace.
unfortunately this change introduces feature test macro checks into
another bits header. at some point these checks should be simplified
by having features.h handle the "FTM X implies Y" relationships.
for synchronous page faults, new in linux commit
1c9725974074a047f6080eecc62c50a8e840d050 and
b6fb293f2497a9841d94f6b57bd2bb2cd222da43
note that only targets that use asm-generic/mman.h have this new
flag defined, so undef it on other targets (mips*, powerpc*).
use the same token to define TIOCSER_TEMT as is used in ioctl.h
so when both headers are included there are no redefinition warnings
during musl build.
most of the found naming differences don't matter to musl, because
internally it unifies the syscall names that vary across targets,
but for external code the names should match the kernel uapi.
aarch64:
__NR_fstatat is called __NR_newfstatat in linux.
__NR_or1k_atomic got mistakenly copied from or1k.
arm:
__NR_arm_sync_file_range is an alias for __NR_sync_file_range2
__NR_fadvise64_64 is called __NR_arm_fadvise64_64 in linux,
the old non-arm name is kept too, it should not cause issues.
(powerpc has similar nonstandard fadvise and it uses the
normal name.)
i386:
__NR_madvise1 was removed from linux in commit
303395ac3bf3e2cb488435537d416bc840438fcb 2011-11-11
microblaze:
__NR_fadvise, __NR_fstatat, __NR_pread, __NR_pwrite
had different name in linux.
mips:
__NR_fadvise, __NR_fstatat, __NR_pread, __NR_pwrite, __NR_select
had different name in linux.
mipsn32:
__NR_fstatat is called __NR_newfstatat in linux.
or1k:
__NR__llseek is called __NR_llseek in linux.
the old name is kept too because that's the name musl uses
internally.
powerpc:
__NR_{get,set}res{gid,uid}32 was never present in powerpc linux.
__NR_timerfd was briefly defined in linux but then got renamed.
it is defined in linux asm/sockios.h since commit
ae40eb1ef30ab4120bd3c8b7e3da99ee53d27a23 (linux v2.6.22)
but was missing from musl by accident.
in musl the sockios macros are exposed in sys/ioctl.h together
with other ioctl requests instead of in sys/socket.h because of
namespace rules. (glibc has them in sys/socket.h under _GNU_SOURCE.)
at one point, clang reportedly failed to support the asm register
constraints needed for inline syscalls. versions of clang that old
have much bigger problems that preclude using them to compile musl
libc.
aarch64, arm, mips, mips64, mipsn32, powerpc, powerpc64 and sh have
cpu feature bits defined in linux for AT_HWCAP auxv entry, so expose
those in sys/auxv.h
it seems the mips hwcaps were never exposed to userspace neither
by linux nor by glibc, but that's most likely an oversight.
placing the opening brace on the same line as the struct keyword/tag
is the style I prefer and seems to be the prevailing practice in more
recent additions.
these changes were generated by the command:
find include/ arch/*/bits -name '*.h' \
-exec sed -i '/^struct [^;{]*$/{N;s/\n/ /;}' {} +
and subsequently checked by hand to ensure that the regex did not pick
up any false positives.
mips and powerpc use their own asm/ioctls.h, not the asm-generic/ioctls.h
and they lack termiox macros that are available on other targets.
see kernel commit 1d65b4a088de407e99714fdc27862449db04fb5c
the (unused) speed fields were omitted when these ports were first
added (within this release cycle, so not present in any release yet)
in accordance with how glibc defines the structure on mips archs.
however their omission does not match existing musl practice/intent.
glibc provides its own, mostly-unified termios structure definition
and performs translation in userspace to match the kernel structure
for the arch, but has gratuitous differences on a few archs like mips,
presumably as a result of historical mistakes. some other libcs use
the kernel definitions directly. musl essentially does that, by
matching the kernel layout in the part of the structure the kernel
will read/write, but leaves additional space at the end for
extensibility. these are nominally the (nonstandard) speed fields and
(on most archs) extra c_cc elements, but since they are not used they
could be repurposed if there's ever a need.
the syscalls take an additional flag argument, they were added in commit
f17d8b35452cab31a70d224964cd583fb2845449 and a RWF_HIPRI priority hint
flag was added to linux/fs.h in 97be7ebe53915af504fb491fb99f064c7cf3cb09.
the syscall is not allocated for microblaze and sh yet.
Szabolcs Nagy
Rich Felker
Bobby Bingham