commit 4486c579cb disabled vdso
clock_gettime on arm due to a Linux kernel bug that was not understood
at the time, whereby the vdso function silently produced
catastrophically wrong results on some systems.
since then, the bug was tracked down to the way the arm kernel
disabled use of vdso clock_gettime on kernels where the necessary
timer was not available or was disabled. it simply patched out the
symbols, but it only did this for the legacy time32 functions, and
left the time64 function in place but non-operational. kernel commit
4405bdf3c57ec28d606bdf5325f1167505bfdcd4 (first present in 5.8)
provided the fix.
if this were a bug that impacted all users of the broken kernel
versions, we could probably ignore it and assume it had been patched
or replaced. however, it's very possible that these kernels appear in
the wild in devices running time32 userspace (glibc, musl 1.1.x, or
some other environment) where they appear to work fine, but where our
new binaries would fail catastrophically if we used the time64 vdso
function.
since the kernel has not (yet?) given us a way to probe for the
working time64 vdso function semantically, we work around the problem
by refusing to use the time64 one unless the time32 one is also
present. this will revert to not using vdso at all if the time32 one
is ever removed, but at least that's safe against wrong results and is
just a missed optimization.
sys/reg.h already had it right as 32, to which it was explicitly
changed when commit 664cd34192 derived
x32 from x86_64. but the copy exposed in sys/user.h was missed.
see
linux commit a49f4f81cb48925e8d7cbd9e59068f516e984144
arch: Wire up Landlock syscalls
linuxcommit 17ae69aba89dbfa2139b7f8024b757ab3cc42f59
Merge tag 'landlock_v34' of ... jmorris/linux-security
Landlock provides for unprivileged application sandboxing. The goal of
Landlock is to enable to restrict ambient rights (e.g. global filesystem
access) for a set of processes. Landlock is inspired by seccomp-bpf but
instead of filtering syscalls and their raw arguments, a Landlock rule
can restrict the use of kernel objects like file hierarchies, according
to the kernel semantic.
PTRACE_OLDSETOPTIONS is old, but it was missing, PTRACE_SYSEMU and
PTRACE_SYSEMU_SINGLESTEP are new, see
linux commit 56e62a73702836017564eaacd5212e4d0fa1c01d
s390: convert to generic entry
new syscall to change the properties of a mount or a mount tree using
file descriptors which the new mount api is based on, see
linux commit 2a1867219c7b27f928e2545782b86daaf9ad50bd
fs: add mount_setattr()
see
linux commit b0a0c2615f6f199a656ed8549d7dce625d77aa77
epoll: wire up syscall epoll_pwait2
linux commit 58169a52ebc9a733aeb5bea857bc5daa71a301bb
epoll: add syscall epoll_pwait2
epoll_wait with struct timespec timeout instead of int. no time32 variant.
When the soft-float ABI for PowerPC was added in commit
5a92dd95c7, with Freescale cpus using
the alternative SPE FPU as the main use case, it was noted that we
could probably support hard float on them, but that it would involve
determining some difficult ABI constraints. This commit is the
completion of that work.
The Power-Arch-32 ABI supplement defines the ABI profiles, and indeed
ATR-SPE is built on ATR-SOFT-FLOAT. But setjmp/longjmp compatibility
are problematic for the same reason they're problematic on ARM, where
optional float-related parts of the register file are "call-saved if
present". This requires testing __hwcap, which is now done.
In keeping with the existing powerpc-sf subarch definition, which did
not have fenv, the fenv macros are not defined for SPE and the SPEFSCR
control register is left (and assumed to start in) the default mode.
commit 6d99ad91e8 introduced this
regression as part of a larger change, based on an incorrect
assumption that rdhwr being part of the mips r2 ISA level meant that
the TLS register, known in the mips documentation as UserLocal, was
unconditionally present on chips providing this ISA level and would
not need trap-and-emulate. this turns out to be false.
based on research by Stanislav Kljuhhin and Abilio Marques, who
reported the problem as a performance regression on certain routers
using OpenWRT vs older uclibc-based versions, it turns out the mips
manuals document the UserLocal register as a feature that might or
might not be implemented or enabled, reflected by a cpu capability bit
in the CONFIG3 register, and that Linux checks for this and has to
explicitly enable it on models that have it.
thus, it's indeed possible that r2+ chips can lack the feature,
bringing us back to the situation where Linux only has a fast
trap-and-emulate path for the case where the destination register is
$3. so, always read the thread pointer through $3. this may incur a
gratuitous move to the desired final register on chips where it's not
needed, but it really doesn't matter.
the kernel structure has padding of the shm_segsz member up to 64
bits, as well as 2 unused longs at the end. somehow that was
overlooked when the powerpc port was added, and it has been broken
ever since; applications compiled with the wrong definition do not
correctly see the shm_segsz, shm_cpid, and shm_lpid members.
fixing the definition just by adding the missing padding would break
the ABI size of the structure as well as the position of the time64
shm_atime and shm_dtime members we added at the end. instead, just
move one of the unused padding members from the original end (before
time64) of the structure to the position of the missing padding. this
preserves size and preserves correct behavior of any compiled code
that was already working. programs affected by the wrong definition
need to be recompiled with the correct one.
mainly added to linux to allow a central process management service in
android to give MADV_COLD|PAGEOUT hints for other processes, see
linux commit ecb8ac8b1f146915aa6b96449b66dd48984caacc
mm/madvise: introduce process_madvise() syscall: an external memory
hinting API
float_t should represent the type that is used to evaluate float
expressions internally. On s390x, float_t is currently set to double.
In contrast, the isa supports single-precision float operations and
compilers by default evaluate float in single precision, which
violates the C standard (sections 5.2.4.2.2 and 7.12 in C11/C17, to be
precise). With -fexcess-precision=standard, gcc evaluates float in
double precision, which aligns with the standard yet at the cost of
added conversion instructions.
gcc-11 will drop the special case to retrofit double precision
behavior for -fexcess-precision=standard so that __FLT_EVAL_METHOD__
will be 0 on s390x in any scenario.
To improve standards compliance and compatibility with future compiler
direction, this patch changes the definition of float_t to be derived
from the compiler's __FLT_EVAL_METHOD__.
see
linux commit 9b4feb630e8e9801603f3cab3a36369e3c1cf88d
arch: wire-up close_range()
linux commit 278a5fbaed89dacd04e9d052f4594ffd0e0585de
open: add close_range()
the ABI type for the vector registers in fpregset_t, struct
fpsimd_context, and struct user_fpsimd_struct is __uint128_t, which
was presumably originally not used because it's a nonstandard type,
but its existence is mandated by the aarch64 psABI. use of the wrong
type here broke software using these structures, and encouraged
incorrect fixes with casts rather than reinterpretation of
representation.
the linux faccessat syscall lacks a flag argument that is necessary
to implement the posix api, see
linux commit c8ffd8bcdd28296a198f237cc595148a8d4adfbe
vfs: add faccessat2 syscall
added in
linux commit 1a50ec0b3b2e9a83f1b1245ea37a853aac2f741c
arm64: Implement archrandom.h for ARMv8.5-RNG
linux commit d4209d8b717311d114b5d47ba7f8249fd44e97c2
arm64: cpufeature: Export matrix and other features to userspace
these were missed before, added in
linux commit 1201937491822b61641c1878ebcd16a93aed4540
arm64: Expose ARMv8.5 CondM capability to userspace
linux commit ca9503fc9e9812aa6258e55d44edb03eb30fc46f
arm64: Expose FRINT capabilities to userspace
also added clone3 on sh and m68k, on sh it's still missing (not
yet wired up), but reserved so safe to add.
see
linux commit fddb5d430ad9fa91b49b1d34d0202ffe2fa0e179
open: introduce openat2(2) syscall
linux commit 9a2cef09c801de54feecd912303ace5c27237f12
arch: wire up pidfd_getfd syscall
linux commit 8649c322f75c96e7ced2fec201e123b2b073bf09
pid: Implement pidfd_getfd syscall
linux commit e8bb2a2a1d51511e6b3f7e08125d52ec73c11139
m68k: Wire up clone3() syscall
the fcntl file locking command macro values in the existing generic
bits/fcntl.h were the "64" variants, requiring 64-bit archs that use
the "plain" variants to have their own bits/fcntl.h, even if they
otherwise use the common definitions for everything.
since commit 7cc79d10af exposed
__LONG_MAX to all bits headers, we can now make the generic one common
between 32- and 64-bit archs.
prior to commit 685e40bb09, x86_64 was
correctly passing O_LARGEFILE to SYS_open; it was removed (defined to
0 in the public header, and changed to use the public definition) as
part of that change, probably out of a mistaken belief that it's not
needed.
however, on a mixed system with 32-bit and 64-bit binaries, it's
important that all files be opened with O_LARGEFILE, even if the
opening process is 64-bit, in case a descriptor is passed to a 32-bit
process. otherwise, attempts to access past 2GB in the 32-bit process
could produce EOVERFLOW.
most 64-bit archs added later got this right alread, except for
mips64. x32 was also affected. there are now fixed.
dtv_copy, canary2, and canary_at_end existed solely to match multiple
ABI and asm-accessed layouts simultaneously. now that pthread_arch.h
can be included before struct __pthread is defined, the struct layout
can depend on macros defined by pthread_arch.h.
the adjustment made is entirely a function of TLS_ABOVE_TP and
TP_OFFSET. aside from avoiding repetition of the TP_OFFSET value and
arithmetic, this change makes pthread_arch.h independent of the
definition of struct __pthread from pthread_impl.h. this in turn will
allow inclusion of pthread_arch.h to be moved to the top of
pthread_impl.h so that it can influence the definition of the
structure.
previously, arch files were very inconsistent about the type used for
the thread pointer. this change unifies the new __get_tp interface to
always use uintptr_t, which is the most correct when performing
arithmetic that may involve addresses outside the actual pointed-to
object (due to TP_OFFSET).
a number of users performing seccomp filtering have requested use of
the new individual syscall numbers for socket syscalls, rather than
the legacy multiplexed socketcall, since the latter has the arguments
all in memory where they can't participate in filter decisions.
previously, some archs used the multiplexed socketcall if it was
historically all that was available, while other archs used the
separate syscalls. the intent was that the latter set only include
archs that have "always" had separate socket syscalls, at least going
back to linux 2.6.0. however, at least powerpc, powerpc64, and sh were
wrongly included in this set, and thus socket operations completely
failed on old kernels for these archs.
with the changes made here, the separate syscalls are always
preferred, but fallback code is compiled for archs that also define
SYS_socketcall. two such archs, mips (plain o32) and microblaze,
define SYS_socketcall despite never having needed it, so it's now
undefined by their versions of syscall_arch.h to prevent inclusion of
useless fallback code.
some archs, where the separate syscalls were only added after the
addition of SYS_accept4, lack SYS_accept. because socket calls are
always made with zeros in the unused argument positions, it suffices
to just use SYS_accept4 to provide a definition of SYS_accept, and
this is done to make happy the macro machinery that concatenates the
socket call name onto __SC_ and SYS_.
signal 7 is SIGEMT on Linux mips* ABI according to the man pages and
kernel. it's not clear where the wrong name came from but it dates
back to original mips commit.
it's been reported that the vdso clock_gettime64 function on (32-bit)
arm is broken, producing erratic results that grow at a rate far
greater than one reported second per actual elapsed second. the vdso
function seems to have been added sometime between linux 5.4 and 5.6,
so if there's ever been a working version, it was only present for a
very short window.
it's not clear what the eventual upstream kernel solution will be, but
something needs to be done on the libc side so as not to be producing
binaries that seem to work on older/existing/lts kernels (which lack
the function and thus lack the bug) but will break fantastically when
moving to newer kernels.
hopefully vdso support will be added back soon, but with a new symbol
name or version from the kernel to allow continued rejection of broken
ones.
Linux defines MAP_SYNC on powerpc and powerpc64 as of commit
22fcea6f85f2 ("mm: move MAP_SYNC to asm-generic/mman-common.h"),
so we can stop undefining it on those architectures.
on all mips variants, Linux did (and maybe still does) have some
syscall return paths that wrongly return both the error flag in r7 and
a negated error code in r2. in particular this happened for at least
some causes of ENOSYS.
add an extra check to only negate the error code if it's positive to
begin with.
bug report and concept for patch by Andreas Dröscher.
commit 4221f154ff added the r7
constraint apparently out of a misunderstanding of the breakage it was
addressing, and did so because the asm was in a shared macro used by
all the __syscallN inline functions. now "+r" is used in the output
section for the forms 4-argument and up, so having it in input is
redundant, and the forms with 0-3 arguments don't need it as an input
at all.
the r2 constraint is kept because without it most gcc versions (seems
to be all prior to 9.x) fail to honor the output register binding for
r2. this seems to be a variant of gcc bug #87733.
both the r7 and r2 input constraints look useless, but the r2 one was
a quiet workaround for gcc bug 87733, which affects all modern
versions prior to 9.x, so it's kept and documented.
exactly revert commit 604f8d3d8b which
was wrong; it caused a major regression on Linux versions prior to
2.6.36. old kernels did not properly preserve r2 across syscall
restart, and instead restarted with the instruction right before
syscall, imposing a contract that the previous instruction must load
r2 from an immediate or a register (or memory) not clobbered by the
syscall.
effectivly revert commit ddc7c4f936
which was wrong; it caused a major regression on Linux versions prior
to 2.6.36. old kernels did not properly preserve r2 across syscall
restart, and instead restarted with the instruction right before
syscall, imposing a contract that the previous instruction must load
r2 from an immediate or a register (or memory) not clobbered by the
syscall.
since other changes were made since, including removal of the struct
stat conversion that was replaced by separate struct kstat, this is
not a direct revert, only a functional one.
the "0"(r2) input constraint added back seems useless/erroneous, but
without it most gcc versions (seems to be all prior to 9.x) fail to
honor the output register binding for r2. this seems to be a variant
of gcc bug #87733. further changes should be made later if a better
workaround is found, but this one has been working since 2012. it
seems this issue was encountered but misidentified then, when it
inspired commit 4221f154ff.
this extends commit 5a105f19b5, removing
timer[fd]_settime and timer[fd]_gettime. the timerfd ones are likely
to have been used in software that started using them before it could
rely on libc exposing functions.
under _GNU_SOURCE for namespace cleanliness, analogous to other archs.
the original placement in sys/reg.h seems not to have been motivated;
such a header isn't even present on other implementations.
some nontrivial number of applications have historically performed
direct syscalls for these operations rather than using the public
functions. such usage is invalid now that time_t is 64-bit and these
syscalls no longer match the types they are used with, and it was
already harmful before (by suppressing use of vdso).
since syscall() has no type safety, incorrect usage of these syscalls
can't be caught at compile-time. so, without manually inspecting or
running additional tools to check sources, the risk of such errors
slipping through is high.
this patch renames the syscalls on 32-bit archs to clock_gettime32 and
gettimeofday_time32, so that applications using the original names
will fail to build without being fixed.
note that there are a number of other syscalls that may also be unsafe
to use directly after the time64 switchover, but (1) these are the
main two that seem to be in widespread use, and (2) most of the others
continue to have valid usage with a null timeval/timespec argument, as
the argument is an optional timeout or similar.
This patch adds an explicit cast to the int arguments passed to the
inline asm used in the RISC-V's implementation of `a_cas`, to ensure
that they are properly sign extended to 64 bits. They aren't
automatically sign extended by Clang, and GCC technically also doesn't
guarantee that they will be sign extended.
the syscall numbers were reserved in v5.3 but not wired up on mips, see
linux commit 0671c5b84e9e0a6d42d22da9b5d093787ac1c5f3
MIPS: Wire up clone3 syscall
mips application specific isa extensions were previously not exported
in hwcaps so userspace could not apply optimized code at runtime.
linux commit 38dffe1e4dde1d3174fdce09d67370412843ebb5
MIPS: elf_hwcap: Export userspace ASEs
the syscall number is reserved on all targets, but it is not wired up
on all targets, see
linux commit 8f6ccf6159aed1f04c6d179f61f6fb2691261e84
Merge tag 'clone3-v5.3' of ... brauner/linux
linux commit 8f3220a806545442f6f26195bc491520f5276e7c
arch: wire-up clone3() syscall
linux commit 7f192e3cd316ba58c88dfa26796cf77789dd9872
fork: add clone3
see
linux commit 7615d9e1780e26e0178c93c55b73309a5dc093d7
arch: wire-up pidfd_open()
linux commit 32fcb426ec001cb6d5a4a195091a8486ea77e2df
pid: add pidfd_open()
