It is checked in vm_map_insert() and vm_map_protect() that PROT_WRITE |
PROT_EXEC are never specified together, if vm_map has MAP_WX flag set.
FreeBSD control flag allows specific binary to request WX exempt, and
there are per ABI boolean sysctls kern.elf{32,64}.allow_wx to enable/
disable globally.
Reviewed by: emaste, jhb
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28050
Also centralize and unify checks to enable ASLR stack gap in a new
helper exec_stackgap().
PR: 239873
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Exec and exit are same as corresponding eventhandler hooks.
Thread exit hook is called somewhat earlier, while thread is still
owned by the process and enough context is available. Note that the
process lock is owned when the hook is called.
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D27309
While there, do some minor cleanup for kclocks. They are only
registered from kern_time.c, make registration function static.
Remove event hooks, they are not used by both registered kclocks.
Add some consts.
Perhaps we can stop registering kclocks at all and statically
initialize them.
Reviewed by: mjg
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D27305
There is no point in dynamic registration, umtx hook is there always.
Reviewed by: mjg
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D27303
No functional change intended.
Tracking these structures separately for each proc enables future work to
correctly emulate clone(2) in linux(4).
__FreeBSD_version is bumped (to 1300130) for consumption by, e.g., lsof.
Reviewed by: kib
Discussed with: markj, mjg
Differential Revision: https://reviews.freebsd.org/D27037
This is mostly mechanical except for vmspace_exit(). There, use the new
refcount_release_if_last() to avoid switching to vmspace0 unless other
processes are sharing the vmspace. In that case, upon switching to
vmspace0 we can unconditionally release the reference.
Remove the volatile qualifier from vm_refcnt now that accesses are
protected using refcount(9) KPIs.
Reviewed by: alc, kib, mmel
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27057
r326145 corrected do_execve() to return EJUSTRETURN upon success so that
important registers are not clobbered. This had the side effect of tapping
out 'failures' for all *execve(2) audit records, which is less than useful
for auditing purposes.
Audit exec returns earlier, where we can know for sure that EJUSTRETURN
translates to success. Note that this unsets TDP_AUDITREC as we commit the
audit record, so the usual audit in the syscall return path will do nothing.
PR: 249179
Reported by: Eirik Oeverby <ltning-freebsd anduin net>
Reviewed by: csjp, kib
MFC after: 1 week
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D26922
and current address space is already destroyed, so kern_execve()
terminates the process.
While there, clean up some internals of post_execve() inlined in init_main.
Reported by: Peter <pmc@citylink.dinoex.sub.org>
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D26525
It keeps recalculated way more often than it is needed.
Provide a routine (fdlastfile) to get it if necessary.
Consumers may be better off with a bitmap iterator instead.
Use AUXARGS_ENTRY_PTR to export these pointers. This is a followup to
r359987 and r359988.
Reviewed by: jhb
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D24446
This simplifies discovery of these values, potentially with reducing the
number of syscalls we need to make at runtime. Longer term, we wish to
convert the startup process to pass an auxargs pointer to _start() and
use that rather than walking off the end of envv. This is cleaner,
more C-friendly, and for systems with strong bounds (e.g. CHERI)
necessary.
Reviewed by: kib
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D24407
Modern debuggers and process tracers use ptrace() rather than procfs
for debugging. ptrace() has a supserset of functionality available
via procfs and new debugging features are only added to ptrace().
While the two debugging services share some fields in struct proc,
they each use dedicated fields and separate code. This results in
extra complexity to support a feature that hasn't been enabled in the
default install for several years.
PR: 244939 (exp-run)
Reviewed by: kib, mjg (earlier version)
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D23837
On machines with SMAP, fueword executes two serializing instructions
which can be seen in microbenchmarks.
As a measure to restore microbenchmark numbers, only read the word on
the attempt to deliver signal in ast(). If the word is set, signal is
not delivered and word is kept, preventing interruption of
interruptible sleeps by signals until userspace calls
sigfastblock(UNBLOCK) which clears the word.
This way, the spurious EINTR that userspace can see while in critical
section is on first interruptible sleep, if a signal is pending, and
on signal posting. It is believed that it is not important for rtld
and lbithr critical sections. It might be visible for the application
code e.g. for the callback of dl_iterate_phdr(3), but again the belief
is that the non-compliance is acceptable. Most important is that the
retry of the sleeping syscall does not interrupt unless additional
signal is posted.
For now I added the knob kern.sigfastblock_fetch_always to enable the
word read on syscall entry to be able to diagnose possible issues due
to spurious EINTR.
While there, do some code restructuting to have all sigfastblock()
handling located in kern_sig.c.
Reviewed by: jeff
Discussed with: mjg
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D23622
A new syscall sigfastblock(2) is added which registers a uint32_t
variable as containing the count of blocks for signal delivery. Its
content is read by kernel on each syscall entry and on AST processing,
non-zero count of blocks is interpreted same as the signal mask
blocking all signals.
The biggest downside of the feature that I see is that memory
corruption that affects the registered fast sigblock location, would
cause quite strange application misbehavior. For instance, the process
would be immune to ^C (but killable by SIGKILL).
With consumers (rtld and libthr added), benchmarks do not show a
slow-down of the syscalls in micro-measurements, and macro benchmarks
like buildworld do not demonstrate a difference. Part of the reason is
that buildworld time is dominated by compiler, and clang already links
to libthr. On the other hand, small utilities typically used by shell
scripts have the total number of syscalls cut by half.
The syscall is not exported from the stable libc version namespace on
purpose. It is intended to be used only by our C runtime
implementation internals.
Tested by: pho
Disscussed with: cem, emaste, jilles
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D12773
Filesystems which want to use it in limited capacity can employ the
VOP_UNLOCK_FLAGS macro.
Reviewed by: kib (previous version)
Differential Revision: https://reviews.freebsd.org/D21427
exec_map_first_page(). This will also enable pagein clustering for other
interested consumers (tmpfs, md, etc).
Discussed with: alc
Approved by: kib
Differential Revision: https://reviews.freebsd.org/D22731
Partially revert r354741 and r354754 and go back to allocating a
fixed-size chunk of stack space for the auxiliary vector. Keep
sv_copyout_auxargs but change it to accept the address at the end of
the environment vector as an input stack address and no longer
allocate room on the stack. It is now called at the end of
copyout_strings after the argv and environment vectors have been
copied out.
This should fix a regression in r354754 that broke the stack alignment
for newer Linux amd64 binaries (and probably broke Linux arm64 as
well).
Reviewed by: kib
Tested on: amd64 (native, linux64 (only linux-base-c7), and i386)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22695
- Use ustringp for the location of the argv and environment strings
and allow destp to travel further down the stack for the stackgap
and auxv regions.
- Update the Linux copyout_strings variants to move destp down the
stack as was done for the native ABIs in r263349.
- Stop allocating a space for a stack gap in the Linux ABIs. This
used to hold translated system call arguments, but hasn't been used
since r159992.
Reviewed by: kib
Tested on: md64 (amd64, i386, linux64), i386 (i386, linux)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22501
Zeroing of them is needed so that an image activator can update the
values as appropriate (or not set at all).
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D22379
Change the FreeBSD ELF ABIs to use this new hook to copyout ELF auxv
instead of doing it in the sv_fixup hook. In particular, this new
hook allows the stack space to be allocated at the same time the auxv
values are copied out to userland. This allows us to avoid wasting
space for unused auxv entries as well as not having to recalculate
where the auxv vector is by walking back up over the argv and
environment vectors.
Reviewed by: brooks, emaste
Tested on: amd64 (amd64 and i386 binaries), i386, mips, mips64
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22355
Atomics are used for page busy and valid state when the shared busy is
held. The details of the locking protocol and valid and dirty
synchronization are in the updated vm_page.h comments.
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21594
This is the first in a series of patches that promotes the page busy field
to a first class lock that no longer requires the object lock for
consistency.
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21548
exec_map_first_page() would unconditionally free an unbacked, invalid
page from the executable image. However, it is possible that the page
is wired, in which case it is incorrect to free the page, so check for
additional wirings first.
Reported by: syzkaller
Tested by: pho
Reviewed by: kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21767
There are several mechanisms by which a vm_page reference is held,
preventing the page from being freed back to the page allocator. In
particular, holding the page's object lock is sufficient to prevent the
page from being freed; holding the busy lock or a wiring is sufficent as
well. These references are protected by the page lock, which must
therefore be acquired for many per-page operations. This results in
false sharing since the page locks are external to the vm_page
structures themselves and each lock protects multiple structures.
Transition to using an atomically updated per-page reference counter.
The object's reference is counted using a flag bit in the counter. A
second flag bit is used to atomically block new references via
pmap_extract_and_hold() while removing managed mappings of a page.
Thus, the reference count of a page is guaranteed not to increase if the
page is unbusied, unmapped, and the object's write lock is held. As
a consequence of this, the page lock no longer protects a page's
identity; operations which move pages between objects are now
synchronized solely by the objects' locks.
The vm_page_wire() and vm_page_unwire() KPIs are changed. The former
requires that either the object lock or the busy lock is held. The
latter no longer has a return value and may free the page if it releases
the last reference to that page. vm_page_unwire_noq() behaves the same
as before; the caller is responsible for checking its return value and
freeing or enqueuing the page as appropriate. vm_page_wire_mapped() is
introduced for use in pmap_extract_and_hold(). It fails if the page is
concurrently being unmapped, typically triggering a fallback to the
fault handler. vm_page_wire() no longer requires the page lock and
vm_page_unwire() now internally acquires the page lock when releasing
the last wiring of a page (since the page lock still protects a page's
queue state). In particular, synchronization details are no longer
leaked into the caller.
The change excises the page lock from several frequently executed code
paths. In particular, vm_object_terminate() no longer bounces between
page locks as it releases an object's pages, and direct I/O and
sendfile(SF_NOCACHE) completions no longer require the page lock. In
these latter cases we now get linear scalability in the common scenario
where different threads are operating on different files.
__FreeBSD_version is bumped. The DRM ports have been updated to
accomodate the KPI changes.
Reviewed by: jeff (earlier version)
Tested by: gallatin (earlier version), pho
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D20486
Otherwise, we might left the boolean set, which would affect cleanup
after an error on interpreter activation.
Reviewed by: markj
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D21560
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
uiomove_object_page() and exec_map_first_page() would previously wire a
page after having grabbed it. Ask vm_page_grab() to perform the wiring
instead: this removes some redundant code, and is cheaper in the case
where the requested page is not resident since the page allocator can be
asked to initialize the page as wired, whereas a separate vm_page_wire()
call requires the page lock.
In vm_imgact_hold_page(), use vm_page_unwire_noq() instead of
vm_page_unwire(PQ_NONE). The latter ensures that the page is dequeued
before returning, but this is unnecessary since vm_page_free() will
trigger a batched dequeue of the page.
Reviewed by: alc, kib
Tested by: pho (part of a larger patch)
MFC after: 1 week
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21440
These vnodes are explicitly opened via VOP_OPEN via
exec_check_permissions identical to the main exectuable image.
Setting ISOPEN allows filesystems to perform suitable checks in
VOP_LOOKUP (e.g. close-to-open consistency in the NFS client).
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D21129
This effectively makes the stack base on the csu _start entry
randomized.
The gap is enabled if ASLR is for the ABI is enabled, and then
kern.elf{64,32}.aslr.stack_gap specify the max percentage of the
initial stack size that can be wasted for gap. Setting it to zero
disables the gap, and max is capped at 50%.
Only amd64 for now.
Reviewed by: cem, markj
Discussed with: emaste
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D21081
The hold_count and wire_count fields of struct vm_page are separate
reference counters with similar semantics. The remaining essential
differences are that holds are not counted as a reference with respect
to LRU, and holds have an implicit free-on-last unhold semantic whereas
vm_page_unwire() callers must explicitly determine whether to free the
page once the last reference to the page is released.
This change removes the KPIs which directly manipulate hold_count.
Functions such as vm_fault_quick_hold_pages() now return wired pages
instead. Since r328977 the overhead of maintaining LRU for wired pages
is lower, and in many cases vm_fault_quick_hold_pages() callers would
swap holds for wirings on the returned pages anyway, so with this change
we remove a number of page lock acquisitions.
No functional change is intended. __FreeBSD_version is bumped.
Reviewed by: alc, kib
Discussed with: jeff
Discussed with: jhb, np (cxgbe)
Tested by: pho (previous version)
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D19247
This allows replacing "sys/eventfilter.h" includes with "sys/_eventfilter.h"
in other header files (e.g., sys/{bus,conf,cpu}.h) and reduces header
pollution substantially.
EVENTHANDLER_DECLARE and EVENTHANDLER_LIST_DECLAREs were moved out of .c
files into appropriate headers (e.g., sys/proc.h, powernv/opal.h).
As a side effect of reduced header pollution, many .c files and headers no
longer contain needed definitions. The remainder of the patch addresses
adding appropriate includes to fix those files.
LOCK_DEBUG and LOCK_FILE_LINE_ARG are moved to sys/_lock.h, as required by
sys/mutex.h since r326106 (but silently protected by header pollution prior
to this change).
No functional change (intended). Of course, any out of tree modules that
relied on header pollution for sys/eventhandler.h, sys/lock.h, or
sys/mutex.h inclusion need to be fixed. __FreeBSD_version has been bumped.
kern_execve() locks text vnode exclusive to be able to set and clear
VV_TEXT flag. VV_TEXT is mutually exclusive with the v_writecount > 0
condition.
The change removes VV_TEXT, replacing it with the condition
v_writecount <= -1, and puts v_writecount under the vnode interlock.
Each text reference decrements v_writecount. To clear the text
reference when the segment is unmapped, it is recorded in the
vm_map_entry backed by the text file as MAP_ENTRY_VN_TEXT flag, and
v_writecount is incremented on the map entry removal
The operations like VOP_ADD_WRITECOUNT() and VOP_SET_TEXT() check that
v_writecount does not contradict the desired change. vn_writecheck()
is now racy and its use was eliminated everywhere except access.
Atomic check for writeability and increment of v_writecount is
performed by the VOP. vn_truncate() now increments v_writecount
around VOP_SETATTR() call, lack of which is arguably a bug on its own.
nullfs bypasses v_writecount to the lower vnode always, so nullfs
vnode has its own v_writecount correct, and lower vnode gets all
references, since object->handle is always lower vnode.
On the text vnode' vm object dealloc, the v_writecount value is reset
to zero, and deadfs vop_unset_text short-circuit the operation.
Reclamation of lowervp always reclaims all nullfs vnodes referencing
lowervp first, so no stray references are left.
Reviewed by: markj, trasz
Tested by: mjg, pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 month
Differential revision: https://reviews.freebsd.org/D19923
PTI mode for the process pmap on exec is activated iff P_MD_PTI is set.
On exec, the existing vmspace can be reused only if pti mode of the
pmap matches the P_MD_PTI flag of the process. Add MD
cpu_exec_vmspace_reuse() callback for exec_new_vmspace() which can
vetoed reuse of the existing vmspace.
MFC note: md_flags change struct proc KBI.
Reviewed by: jhb, markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D19514
With this change, randomization can be enabled for all non-fixed
mappings. It means that the base address for the mapping is selected
with a guaranteed amount of entropy (bits). If the mapping was
requested to be superpage aligned, the randomization honours the
superpage attributes.
Although the value of ASLR is diminshing over time as exploit authors
work out simple ASLR bypass techniques, it elimintates the trivial
exploitation of certain vulnerabilities, at least in theory. This
implementation is relatively small and happens at the correct
architectural level. Also, it is not expected to introduce
regressions in existing cases when turned off (default for now), or
cause any significant maintaince burden.
The randomization is done on a best-effort basis - that is, the
allocator falls back to a first fit strategy if fragmentation prevents
entropy injection. It is trivial to implement a strong mode where
failure to guarantee the requested amount of entropy results in
mapping request failure, but I do not consider that to be usable.
I have not fine-tuned the amount of entropy injected right now. It is
only a quantitive change that will not change the implementation. The
current amount is controlled by aslr_pages_rnd.
To not spoil coalescing optimizations, to reduce the page table
fragmentation inherent to ASLR, and to keep the transient superpage
promotion for the malloced memory, locality clustering is implemented
for anonymous private mappings, which are automatically grouped until
fragmentation kicks in. The initial location for the anon group range
is, of course, randomized. This is controlled by vm.cluster_anon,
enabled by default.
The default mode keeps the sbrk area unpopulated by other mappings,
but this can be turned off, which gives much more breathing bits on
architectures with small address space, such as i386. This is tied
with the question of following an application's hint about the mmap(2)
base address. Testing shows that ignoring the hint does not affect the
function of common applications, but I would expect more demanding
code could break. By default sbrk is preserved and mmap hints are
satisfied, which can be changed by using the
kern.elf{32,64}.aslr.honor_sbrk sysctl.
ASLR is enabled on per-ABI basis, and currently it is only allowed on
FreeBSD native i386 and amd64 (including compat 32bit) ABIs. Support
for additional architectures will be added after further testing.
Both per-process and per-image controls are implemented:
- procctl(2) adds PROC_ASLR_CTL/PROC_ASLR_STATUS;
- NT_FREEBSD_FCTL_ASLR_DISABLE feature control note bit makes it possible
to force ASLR off for the given binary. (A tool to edit the feature
control note is in development.)
Global controls are:
- kern.elf{32,64}.aslr.enable - for non-fixed mappings done by mmap(2);
- kern.elf{32,64}.aslr.pie_enable - for PIE image activation mappings;
- kern.elf{32,64}.aslr.honor_sbrk - allow to use sbrk area for mmap(2);
- vm.cluster_anon - enables anon mapping clustering.
PR: 208580 (exp runs)
Exp-runs done by: antoine
Reviewed by: markj (previous version)
Discussed with: emaste
Tested by: pho
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D5603
Code after exec_fail_dealloc label expects that the image vnode is
locked if present. When copyout() of the strings or auxv vectors fails,
goto to the error handling did not relocked the vnode as required.
The copyout() can be made failing e.g. by creating an ELF image with
PT_GNU_STACK segment disabling the write.
Reported by: Jonathan Stuart <n0t.jcs@gmail.com> (found by fuzzing)
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Given a zeroed struct image_args with an allocated buf member,
exec_args_add_fname() must be called to install a file name (or NULL).
Then zero or more calls to exec_args_add_env() followed by zero or
more calls to exec_args_add_env(). exec_args_adjust_args() may be
called after args and/or env to allow an interpreter to be prepended to
the argument list.
To allow code reuse when adding arg and env variables, begin_envv
should be accessed with the accessor exec_args_get_begin_envv()
which handles the case when no environment entries have been added.
Use these functions to simplify exec_copyin_args() and
freebsd32_exec_copyin_args().
Reviewed by: kib
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D15468
