These functions (sigandset, sigisemptyset, sigorset) are commonly available
in at least musl libc and glibc; sigorset, at least, has proven quite useful
in qemu-bsd-user work for tracking the current process signal mask in a more
self-documenting/aesthetically pleasing manner.
Reviewed by: bapt, jilles, pfg
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D22187
Update a bunch of Makefile.depend files as
a result of adding Makefile.depend.options files
Reviewed by: bdrewery
MFC after: 1 week
Sponsored by: Juniper Networks
Differential Revision: https://reviews.freebsd.org/D22494
Leaf directories that have dependencies impacted
by options need a Makefile.depend.options file
to avoid churn in Makefile.depend
DIRDEPS for cases such as OPENSSL, TCP_WRAPPERS etc
can be set in local.dirdeps-options.mk
which can add to those set in Makefile.depend.options
See share/mk/dirdeps-options.mk
Reviewed by: bdrewery
MFC after: 1 week
Sponsored by: Juniper Networks
Differential Revision: https://reviews.freebsd.org/D22469
As mandated by POSIX. Also clarify the kill(2) manpage.
While there, restructure the code in killpg1() to use helper which
keeps overall state of the process list iteration in the killpg1_ctx
structued, later used to infer the error returned.
Reported by: amdmi3
Reviewed by: jilles
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D22621
Conditional branch and jump instructions do not always call via PLT
stubs and thus will not honor LD_PRELOAD, etc. lld warns about using
non-preemptible relocations for preemptible or unknown symbols whereas
bfd does not (at least for RISC-V).
Reviewed by: br, James Clarke
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22658
This saves an instruction in each case as well as an extra memory
indirection via the GOT for PIC code.
Reviewed by: br, James Clarke
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22656
o Remove All Rights Reserved from my notices
o imp@FreeBSD.org everywhere
o regularize punctiation, eliminate date ranges
o Make sure that it's clear that I don't claim All Rights reserved by listing
All Rights Reserved on same line as other copyright holders (but not
me). Other such holders are also listed last where it's clear.
Theoretically, this was breaking the size calculation for the symbol.
Noticed when doing a readthrough.
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D22525
Due to ELFv1 specific code in _ctx_start.S and makecontext.c, userspace
context switching was completely broken on ELFv2.
With this change, we now pass the libthr test suite.
Approved by: jhibbits (mentor)
Differential Revision: https://reviews.freebsd.org/D22421
Add ifdefs in the assembler for soft-float compile case.
Submitted by: Hiroki Mori
Reviewed by: ray@
Differential Review: https://reviews.freebsd.org/D22352
__has_attribute(__constructor__) is a better test for clang than
defined(__clang__). Switch to it instead.
While we're already here and touching it, pfg@ nailed down when GCC actually
introduced the priority argument -- 4.3. Use that instead of our
hammer-guess of GCC >= 5 for the sake of correctness.
The preproc logic was added at the last minute to appease GCC 4.2, and
kevans@ did clearly not go back and double-check that the logic worked out
for clang builds to use the new variant.
It turns out that clang defines __GNUC__ == 4. Flip it around and check
__clang__ as well, leaving a note to remove it later.
Reported by: cem
First, this commit is a NOP on GCC <= 4.x; this decidedly doesn't work
cleanly on GCC 4.2, and it will be gone soon anyways so I chose not to dump
time into figuring out if there's a way to make it work. xtoolchain-gcc,
clocking in as GCC6, can cope with it just fine and later versions are also
generally ok with the syntax. I suspect very few users are running GCC4.2
built worlds and also experiencing potential fallout from the status quo.
For dynamically linked applications, this change also means very little.
rtld will run libc ctors before most others, so the situation is
approximately a NOP for these as well.
The real cause for this change is statically linked applications doing
almost questionable things in their constructors. qemu-user-static, for
instance, creates a thread in a global constructor for their async rcu
callbacks. In general, this works in other places-
- On OpenBSD, __stack_chk_guard is stored in an .openbsd.randomdata section
that's initialized by the kernel in the static case, or ld.so in the
dynamic case
- On Linux, __stack_chk_guard is apparently stored in TLS and such a problem
is circumvented there because the value is presumed stable in the new
thread.
On FreeBSD, the rcu thread creation ctor and __guard_setup are both unmarked
priority. qemu-user-static spins up the rcu thread prior to __guard_setup
which starts making function calls- some of these are sprinkled with the
canary. In the middle of one of these functions, __guard_setup is invoked in
the main thread and __stack_chk_guard changes- qemu-user-static is promptly
terminated for an SSP violation that didn't actually happen.
This is not an all-too-common problem. We circumvent it here by giving the
__stack_chk_guard constructor a solid priority. 200 was chosen because that
gives static applications ample range (down to 101) for working around it
if they really need to. I suspect most applications will "just work" as
expected- the default/non-prioritized flavor of __constructor__ functions
run last, and the canary is generally not expected to change as of this
point at the very least.
This took approximately three weeks of spare time debugging to pin down.
PR: 241905
Even though clang comes with a number of internal CUDA wrapper headers,
compiling sample CUDA programs will result in errors similar to:
In file included from <built-in>:1:
In file included from /usr/lib/clang/9.0.0/include/__clang_cuda_runtime_wrapper.h:204:
/usr/home/arr/cuda/var/cuda-repo-10-0-local-10.0.130-410.48/usr/local/cuda-10.0//include/crt/math_functions.hpp:2910:7: error: no matching function for call to '__isnan'
if (__isnan(a)) {
^~~~~~~
/usr/lib/clang/9.0.0/include/__clang_cuda_device_functions.h:460:16: note: candidate function not viable: call to __device__ function from __host__ function
__DEVICE__ int __isnan(double __a) { return __nv_isnand(__a); }
^
CUDA expects __isnan() and __isnanf() declarations to be available,
which are glibc specific extensions, equivalent to the regular isnan()
and isnanf().
To provide these, define __isnan() and __isnanf() as aliases of the
already existing static inline functions __inline_isnan() and
__inline_isnanf() from math.h.
Reported by: arrowd
PR: 241550
MFC after: 1 week
This warning (comparing a pointer against a zero character literal
rather than NULL) has existed since GCC 7.1.0, and was recently added to
Clang trunk.
Almost all of these are harmless, except for fwcontrol's str2node, which
needs to both guard against dereferencing a NULL pointer (though in
practice it appears none of the callers will ever pass one in), as well
as ensure it doesn't parse the empty string as node 0 due to strtol's
awkward interface.
Submitted by: James Clarke <jtrc27@jrtc27.com>
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D21914
While FreeBSD's implementation of these expect an int inside of libc, that's an
implementation detail that we can hide from the user as it's the natural
promotion of the current mode_t type and before it is used in the kernel, it's
converted back to the narrower type that's the current definition of mode_t. As
such, documenting int is at best confusing and at worst misleading. Instead add
a note that these args are variadic and as such calling conventions may differ
from non-variadic arguments.
promoted to ints).
- `mode_t` is `uint16_t` (`sys/sys/_types.h`)
- `openat` takes variadic args
- variadic args cannot be 16-bit, and indeed the code uses int
- the manpage currently kinda implies the argument is 16-bit by saying `mode_t`
Prompted by Rust things: https://github.com/tailhook/openat/issues/21
Submitted by: Greg V at unrelenting
Differential Revision: https://reviews.freebsd.org/D21816
Add an atomic shm rename operation, similar in spirit to a file
rename. Atomically unlink an shm from a source path and link it to a
destination path. If an existing shm is linked at the destination
path, unlink it as part of the same atomic operation. The caller needs
the same permissions as shm_unlink to the shm being renamed, and the
same permissions for the shm at the destination which is being
unlinked, if it exists. If those fail, EACCES is returned, as with the
other shm_* syscalls.
truss support is included; audit support will come later.
This commit includes only the implementation; the sysent-generated
bits will come in a follow-on commit.
Submitted by: Matthew Bryan <matthew.bryan@isilon.com>
Reviewed by: jilles (earlier revision)
Reviewed by: brueffer (manpages, earlier revision)
Relnotes: yes
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D21423
Described in [1], signal handlers running in a vfork child have
opportunities to corrupt the parent's state. Address this by adding a new
rfork(2) flag, RFSPAWN, that has vfork(2) semantics but also resets signal
handlers in the child during creation.
x86 uses rfork_thread(3) instead of a direct rfork(2) because rfork with
RFMEM/RFSPAWN cannot work when the return address is stored on the stack --
further information about this problem is described under RFMEM in the
rfork(2) man page.
Addressing this has been identified as a prerequisite to using posix_spawn
in subprocess on FreeBSD [2].
[1] https://ewontfix.com/7/
[2] https://bugs.python.org/issue35823
Reviewed by: jilles, kib
Differential Revision: https://reviews.freebsd.org/D19058
When RFSPAWN is passed, rfork exhibits vfork(2) semantics but also resets
signal handlers in the child during creation to avoid a point of corruption
of parent state from the child.
This flag will be used by posix_spawn(3) to handle potential signal issues.
Reviewed by: jilles, kib
Differential Revision: https://reviews.freebsd.org/D19058
memfd_create is effectively a SHM_ANON shm_open(2) mapping with optional
CLOEXEC and file sealing support. This is used by some mesa parts, some
linux libs, and qemu can also take advantage of it and uses the sealing to
prevent resizing the region.
This reimplements shm_open in terms of shm_open2(2) at the same time.
shm_open(2) will be moved to COMPAT12 shortly.
Reviewed by: markj, kib
Differential Revision: https://reviews.freebsd.org/D21393
bde reports (in a reply to r351700 commit mail):
This uses scasb, which was last optimal on the 8086, or perhaps the
original i386. On freefall, it is several times slower than the
naive translation of the naive C code.
Reported by: bde
Reviewed by: kib, markj
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21785
The two options are
* nocover/cover: Prevent/allow mounting over an existing root mountpoint.
E.g., "mount -t ufs -o nocover /dev/sd1a /usr/local" will fail if /usr/local
is already a mountpoint.
* emptydir/noemptydir: Prevent/allow mounting on a non-empty directory.
E.g., "mount -t ufs -o emptydir /dev/sd1a /usr" will fail.
Neither of these options is intended to be a default, for historical and
compatibility reasons.
Reviewed by: allanjude, kib
Differential Revision: https://reviews.freebsd.org/D21458
calls to max allowed UDP datagram size.
Since max allowed size both for keys and values where increased, the
old sizes of around 1K cause ypmatch(3) failures, while plain maps
fetches work.
The buffers were reduced in r34146 from default UDP rpcclient values
to 1024/2304 due to the key and value size being 1K.
Reviewed by: slavash
Sponsored by: Mellanox Technologies
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D21586
- Fix the statement that big5 is a de facto standard of Traditional Chinese
text [1]
- Add a BUGS section describes the problem of big5 and suggests use utf8
PR: 189095
Submitted by: Brennan Vincent <brennan@umanwizard.com> [1]
Reviewed by: Ting-Wei Lan <lantw44@gmail.com>
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21622
When SO_TIMESTAMP is set, the kernel will attempt to attach a timestamp as
ancillary data to each IP datagram that is received on the socket. However,
it may fail, for example due to insufficient memory. In that case the
packet will still be received but not timestamp will be attached.
Reviewed by: kib
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D21607
heap buffer overflow. This was discovered by a Google fuzzer test.
This can lead to remote denial of service. User interaction and
execution privileges are not a prerequisite for exploitation.
Reported by: enh at Google, to FreeBSD by maya@NetBSD.org
Obtained from: enh at Google
See also: NetBSD ns_name.c r1.12
Reviewed by: delphij, ume
MFC after: 3 days
https://android-review.googlesource.com/c/platform/bionic/+/1093130
Differential Revision: https://reviews.freebsd.org/D21523
It allows a process to request that stack gap was not applied to its
stacks, retroactively. Also it is possible to control the gaps in the
process after exec.
PR: 239894
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D21352
Previously userspace would issue one syscall to resolve the sysctl and then
another one to actually use it. Do it all in one trip.
Fallback is provided in case newer libc happens to be running on an older
kernel.
Submitted by: Pawel Biernacki
Reported by: kib, brooks
Differential Revision: https://reviews.freebsd.org/D17282
Parentheses added to HASZERO macro to avoid a GCC warning.
Reviewed by: kib, mjg
Obtained from: musl (snapshot at commit 4d0a82170a)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17631
The symbol version for _mcount was removed 12 years ago in r169525 from
gmon/Symbol.map, to be added to the per-arch Symbol.map. mips was overlooked
in this, so _mcount has no symver. Add it back to where it should have been,
rather than where it would go if it were added today, since we're correcting
a historical mistake.
Additionally, _mcount is getting thrown into .mdebug.abi32 in the llvm80/90
world as it's not getting explicitly thrown into .text, so do this now. This
fixes the libc build that was previously failing due to relocations in
.mdebug.abi32. This is specifically due to the way clang's integrated AS
works and that they emit the .mdebug.abiNN section early in the process. An
LLVM bug has been submitted[0] and an agreement has been made that the
mips backend should switch to .text following .mdebug.abiNN for
compatibility.
[0] https://bugs.llvm.org/show_bug.cgi?id=43119
Reviewed by: imp, arichardson
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D21435
gets is unsafe and shouldn't be used (for many years now). Leave it in
the existing symbol version so anything that previously linked aginst it
still runs, but do not allow new software to link against it.
(The compatability/legacy implementation must not be static so that
the symbol and in particular the compat sym gets@FBSD_1.0 make it
into libc.)
PR: 222796 (exp-run)
Reported by: Paul Vixie
Reviewed by: allanjude, cy, eadler, gnn, jhb, kib, ngie (some earlier)
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D12298
This unskips:
- lib.libc.stdlib.strtod_test.strtod_round
- lib.msun.fe_round_test.t_nofe_round
In lib/msun/tests/Makefile only define on fe_round_test.c because
lib.msun.ilogb_test.ilogb will get wrong results and needs more examination.
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
machine/regnum.h ends up being included by sys/procfs.h and sys/ptrace.h via
machine/reg.h. Many of the regnum definitions are too short and too generic
to be exposing to any userland application including one of these two
headers. Moreover, these actively cause build failures in googletest
(template <typename T1 ...> expanding to template <typename 9 ...>).
Hide the definitions behind _KERNEL or _WANT_MIPS_REGNUM, and patch all of
the userland consumers to define as needed.
Discussed with: imp, jhb
Reviewed by: imp, jhb
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D21330
Although libc syscall wrappers do not get checked in this can aid in
finding the source of generated files when spelunking in the objdir.
Multiple tools use @generated to identify generated files (for example,
in a review Phabricator will by default hide diffs in generated files).
For consistency use the @generated tag in makesyscalls.sh as we've done
for other generated files, even though these wrappers aren't checked in
to the tree.
Use quad.h from libc instead for the time being. This reduces the number of
nearly-identical-quad.h we have in tree to two with only minor changes.
Prototypes for some *sh*di3 have been added to match the copy in libkern.
The differences between the two are likely few enough that they can perhaps
be merged with little additional effort to bring us down to 1.
MFC after: 3 days
Since YP protocol definition uses the constant to declare
variable-size opaque byte strings, the change should be binary
compatible with existing installations which do not expose keys or
values larger than 1024 bytes.
All uses of local variables with YPMAXRECORD sizes were removed to
avoid insane stack use. On the other hand, variables with static
lifetime should be fine and only result in increased VA use.
Glibc made same change, increasing the allowed length for keys and
values in YP to 16M, in 2013.
Reviewed by: markj
Discussed with: ian
Sponsored by: Mellanox Technologies
MFC after: 3 weeks
Differential revision: https://reviews.freebsd.org/D20900
If the length of the source wide character string, passed in via the
"size_t n" parameter, is set to zero, the function should only return
the required length for the destination wide character string. In this
case, it should *not* attempt to write to the destination, so the "dst"
parameter is permitted to be NULL.
However, when the internally called _collate_wxfrm() function returns an
error, such as when using the "C" locale, as a fallback wcscpy(3) or
wcsncpy(3) are used. But if the input length is zero, wcsncpy(3) will
be called with a length of -1! If the "dst" parameter is NULL, this
will immediately result in a segfault, or if "dst" is a valid pointer,
it will most likely result in unexpectedly overwritten memory.
Fix this by explicitly checking for an input length greater than zero,
before calling wcsncpy(3).
Note that a similar situation does not occur in strxfrm(3), the plain
character version of this function, as it uses strlcpy(3) for the error
case. The strlcpy(3) function does not write to the destination if the
input length is zero.
MFC after: 1 week
This is a variant of mkostemps() which takes a directory descriptor and
returns a descriptor for a tempfile relative to that directory. Unlike
the other mktemp functions, mkostempsat() can be used in capability
mode.
Reviewed by: cem
Discussed with: brooks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21031
copy_file_range.2 is a new man page (content change).
Reviewed by: kib, asomers
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D20584
fusefs file systems may have a fsname subtype (set by mount_fusefs's "-o
subtype" option) that gets appended to the fsname as returned by statfs(2).
The subtype is set on a per-mount basis so it isn't part of the struct
vfsconf. Special-case getvfsbyname to match either the full "fusefs.foobar"
or short "fusefs" fsname.
This is a merge of r348007, r348054, and r350093 from projects/fuse2
Reviewed by: kib
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21043
This avoids reading past the end of the static strings. On a system
with bounds checking these tests fault.
Reviewed by: asomers
Obtained from: CheriBSD
MFC after: 1 week
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D21004
In some circumstances, setmode(3) may call umask(2) twice to retrieve
the current mode and then restore it. Between calls, the process will
have a umask of 0.
Reviewed by: markj
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D20982
This ptrace operation returns a structure containing the error and
return values from the current system call. It is only valid when a
thread is stopped during a system call exit (PL_FLAG_SCX is set).
The sr_error member holds the error value from the system call. Note
that this error value is the native FreeBSD error value that has _not_
been translated to an ABI-specific error value similar to the values
logged to ktrace.
If sr_error is zero, then the return values of the system call will be
set in sr_retval[0] and sr_retval[1].
Reviewed by: kib
MFC after: 1 month
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D20901
NetBSD and OpenBSD have libc wrapper functions for the ARM_SYNC_ICACHE and
ARM_DRAIN_WRITEBUF sysarch operations. This change adds compatible functions
to our library. This should make it easier for various upstream sources to
support *BSD operating systems with a single variation of cache maintence
code in tools like interpreters and JIT compilers.
I consider the argument types passed to arm_sync_icache() to be especially
unfortunate, but this is intended to match the other BSDs.
Differential Revision: https://reviews.freebsd.org/D20906
Take part of the text from POSIX 2018 edition and describe the
atomicity requirements for read and write syscalls. See p1003.1-2018,
Vol.2, 2.9.7 Threads interaction with Regular File Operations.
Reviewed by: asomers
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Differential revision: https://reviews.freebsd.org/D20867
feature bit.
In particular, allocate the bit to opt-out the image from implicit
PROTMAX enablement. Provide procctl(2) verbs to set and query
implicit PROTMAX handling. The knobs mimic the same per-image flag
and per-process controls for ASLR.
Reviewed by: emaste, markj (previous version)
Discussed with: brooks
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D20795
Currently RTLD is linked against libc_nossp_pic which means that any libc
symbol used in rtld can pull in a lot of depedencies. This was causing
symbol such as __libc_interposing and all the pthread stubs to be included
in RTLD even though they are not required. It turns out most of these
dependencies can easily be avoided by providing overrides inside of rtld.
This change is motivated by CHERI, where we have an experimental ABI that
requires additional relocation processing to allow the use of function
pointers inside of rtld. Instead of adding this self-relocation code to
RTLD I attempted to remove most function pointers from RTLD and discovered
that most of them came from the libc dependencies instead of being actually
used inside rtld.
A nice side-effect of this change is that rtld is now 22% smaller on amd64.
text data bss dec hex filename
0x21eb6 0xce0 0xe60 145910 239f6 /home/alr48/ld-elf-x86.before.so.1
0x1a6ed 0x728 0xdd8 113645 1bbed /home/alr48/ld-elf-x86.after.so.1
The number of R_X86_64_RELATIVE relocations that need to be processed on
startup has also gone down from 368 to 187 (almost 50% less).
Reviewed By: kib
Differential Revision: https://reviews.freebsd.org/D20663
Summary:
PowerPC has two PLT models: BSS-PLT and Secure-PLT. BSS-PLT uses runtime
code generation to generate the PLT stubs. Secure-PLT was introduced with
GCC 4.1 and Binutils 2.17 (base has GCC 4.2.1 and Binutils 2.17), and is a
more secure PLT format, using a read-only linkage table, with the dynamic
linker populating a non-executable index table.
This is the libc, rtld, and kernel support only. The toolchain and build
parts will be updated separately.
Reviewed By: nwhitehorn, bdragon, pfg
Differential Revision: https://reviews.freebsd.org/D20598
MFC after: 1 month
This is in preparation for compiling these files as part of rtld (which is
built with WARNS=6). See https://reviews.freebsd.org/D20663 for more details.
In the case of mmap(), add a HISTORY section. Mention that mmap() and
mprotect()'s documentation predates an implementation. The
implementation first saw wide use in 4.3-Reno, but there seems to be no
easy way to express that in mdoc so stick with 4.4BSD.
Reviewed by: emaste
Requested by: cem
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D20713
A new macro PROT_MAX() alters a protection value so it can be OR'd with
a regular protection value to specify the maximum permissions. If
present, these flags specify the maximum permissions.
While these flags are non-portable, they can be used in portable code
with simple ifdefs to expand PROT_MAX() to 0.
This change allows (e.g.) a region that must be writable during run-time
linking or JIT code generation to be made permanently read+execute after
writes are complete. This complements W^X protections allowing more
precise control by the programmer.
This change alters mprotect argument checking and returns an error when
unhandled protection flags are set. This differs from POSIX (in that
POSIX only specifies an error), but is the documented behavior on Linux
and more closely matches historical mmap behavior.
In addition to explicit setting of the maximum permissions, an
experimental sysctl vm.imply_prot_max causes mmap to assume that the
initial permissions requested should be the maximum when the sysctl is
set to 1. PROT_NONE mappings are excluded from this for compatibility
with rtld and other consumers that use such mappings to reserve
address space before mapping contents into part of the reservation. A
final version this is expected to provide per-binary and per-process
opt-in/out options and this sysctl will go away in its current form.
As such it is undocumented.
Reviewed by: emaste, kib (prior version), markj
Additional suggestions from: alc
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D18880
The man page claims that with O_FSYNC (aka O_SYNC) the kernel will not cache
written data. However, that's not true. Nor does POSIX require it.
Perhaps it was true when that section of the man page was written in r69336
(I haven't checked). But it's not true now. Now the effect is simply that
writes are sent to disk immediately and synchronously, but they're still
cached.
See also: https://pubs.opengroup.org/onlinepubs/9699919799/
See also: ffs_write in sys/ufs/ffs/ffs_vnops.c
Reviewed by: cem
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D20641
