Use PCID to avoid complete TLB shootdown when switching between user
and kernel mode with PTI enabled.
I use the model close to what I read about KAISER, user-mode PCID has
1:1 correspondence to the kernel-mode PCID, by setting bit 11 in PCID.
Full kernel-mode TLB shootdown is performed on context switches, since
KVA TLB invalidation only works in the current pmap. User-mode part of
TLB is flushed on the pmap activations as well.
Similarly, IPI TLB shootdowns must handle both kernel and user address
spaces for each address. Note that machines which implement PCID but
do not have INVPCID instructions, cause the usual complications in the
IPI handlers, due to the need to switch to the target PCID temporary.
This is racy, but because for PCID/no-INVPCID we disable the
interrupts in pmap_activate_sw(), IPI handler cannot see inconsistent
state of CPU PCID vs PCPU pmap/kcr3/ucr3 pointers.
On the other hand, on kernel/user switches, CR3_PCID_SAVE bit is set
and we do not clear TLB.
I can imagine alternative use of PCID, where there is only one PCID
allocated for the kernel pmap. Then, there is no need to shootdown
kernel TLB entries on context switch. But copyout(3) would need to
either use method similar to proc_rwmem() to access the userspace
data, or (in reverse) provide a temporal mapping for the kernel buffer
into user mode PCID and use trampoline for copy.
Reviewed by: markj (previous version)
Tested by: pho
Discussed with: alc (some aspects)
Sponsored by: The FreeBSD Foundation
MFC after: 3 weeks
Differential revision: https://reviews.freebsd.org/D13985
When PTI is enabled, empty IDT slots point to rsvd_pti.
Reported by: Dexuan-BSD Cui <dexuan.bsd@gmail.com>
Sponsored by: The FreeBSD Foundation
MFC after: 5 days
When allocating memory through malloc(9), we always expect the amount of
memory requested to be unsigned as a negative value would either stand for
an error or an overflow.
Unsign some values, found when considering the use of mallocarray(9), to
avoid unnecessary casting. Also consider that indexes should be of
at least the same size/type as the upper limit they pretend to index.
MFC after: 3 weeks
Uses of mallocarray(9).
The use of mallocarray(9) has rocketed the required swap to build FreeBSD.
This is likely caused by the allocation size attributes which put extra pressure
on the compiler.
Given that most of these checks are superfluous we have to choose better
where to use mallocarray(9). We still have more uses of mallocarray(9) but
hopefully this is enough to bring swap usage to a reasonable level.
Reported by: wosch
PR: 225197
Kernel Page Table Isolation (KPTI) was introduced in r328083 as a
mitigation for the 'Meltdown' vulnerability. AMD CPUs are not affected,
per https://www.amd.com/en/corporate/speculative-execution:
We believe AMD processors are not susceptible due to our use of
privilege level protections within paging architecture and no
mitigation is required.
Thus default KPTI to off for AMD CPUs, and to on for others. This may
be refined later as we obtain more specific information on the sets of
CPUs that are and are not affected.
Submitted by: Mitchell Horne
Reviewed by: cem
Relnotes: Yes
Security: CVE-2017-5754
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D13971
The implementation of the Kernel Page Table Isolation (KPTI) for
amd64, first version. It provides a workaround for the 'meltdown'
vulnerability. PTI is turned off by default for now, enable with the
loader tunable vm.pmap.pti=1.
The pmap page table is split into kernel-mode table and user-mode
table. Kernel-mode table is identical to the non-PTI table, while
usermode table is obtained from kernel table by leaving userspace
mappings intact, but only leaving the following parts of the kernel
mapped:
kernel text (but not modules text)
PCPU
GDT/IDT/user LDT/task structures
IST stacks for NMI and doublefault handlers.
Kernel switches to user page table before returning to usermode, and
restores full kernel page table on the entry. Initial kernel-mode
stack for PTI trampoline is allocated in PCPU, it is only 16
qwords. Kernel entry trampoline switches page tables. then the
hardware trap frame is copied to the normal kstack, and execution
continues.
IST stacks are kept mapped and no trampoline is needed for
NMI/doublefault, but of course page table switch is performed.
On return to usermode, the trampoline is used again, iret frame is
copied to the trampoline stack, page tables are switched and iretq is
executed. The case of iretq faulting due to the invalid usermode
context is tricky, since the frame for fault is appended to the
trampoline frame. Besides copying the fault frame and original
(corrupted) frame to kstack, the fault frame must be patched to make
it look as if the fault occured on the kstack, see the comment in
doret_iret detection code in trap().
Currently kernel pages which are mapped during trampoline operation
are identical for all pmaps. They are registered using
pmap_pti_add_kva(). Besides initial registrations done during boot,
LDT and non-common TSS segments are registered if user requested their
use. In principle, they can be installed into kernel page table per
pmap with some work. Similarly, PCPU can be hidden from userspace
mapping using trampoline PCPU page, but again I do not see much
benefits besides complexity.
PDPE pages for the kernel half of the user page tables are
pre-allocated during boot because we need to know pml4 entries which
are copied to the top-level paging structure page, in advance on a new
pmap creation. I enforce this to avoid iterating over the all
existing pmaps if a new PDPE page is needed for PTI kernel mappings.
The iteration is a known problematic operation on i386.
The need to flush hidden kernel translations on the switch to user
mode make global tables (PG_G) meaningless and even harming, so PG_G
use is disabled for PTI case. Our existing use of PCID is
incompatible with PTI and is automatically disabled if PTI is
enabled. PCID can be forced on only for developer's benefit.
MCE is known to be broken, it requires IST stack to operate completely
correctly even for non-PTI case, and absolutely needs dedicated IST
stack because MCE delivery while trampoline did not switched from PTI
stack is fatal. The fix is pending.
Reviewed by: markj (partially)
Tested by: pho (previous version)
Discussed with: jeff, jhb
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
The static atrtc_set() function was called only from clock_settime(), so
just move its contents entirely into clock_settime() and delete atrtc_set().
Rename the struct bcd_clocktime variables from 'ct' to 'bct'. I had
originally wanted to emphasize how identical the clocktime and bcd_clocktime
structs were, but things evolved to the point where the structs are not at
all identical anymore, so now emphasizing the difference seems better.
related series of operations without doing a lock/unlock for each byte.
Use them when reading and writing the entire set of time registers.
The original rtcin() and writertc() functions which do lock/unlock on each
byte still exist, because they are public and called by outside code.
Focus on code where we are doing multiplications within malloc(9). None of
these ire likely to overflow, however the change is still useful as some
static checkers can benefit from the allocation attributes we use for
mallocarray.
This initial sweep only covers malloc(9) calls with M_NOWAIT. No good
reason but I started doing the changes before r327796 and at that time it
was convenient to make sure the sorrounding code could handle NULL values.
X-Differential revision: https://reviews.freebsd.org/D13837
New common routines were added to kern/subr_clock.c for converting between
calendrical time expressed in BCD and struct timespec. The new functions
return EINVAL on error, as expected when the clock hardware does not provide
valid time.
PR: 224813
Differential Revision: https://reviews.freebsd.org/D13731 (no reviewers)
allocated with a tag to come from the specified domain if it meets the
other constraints provided by the tag. Automatically create a tag at
the root of each bus specifying the domain local to that bus if
available.
Reviewed by: jhb, kib
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D13545
userspace to control NUMA policy administratively and programmatically.
Implement domainset based iterators in the page layer.
Remove the now legacy numa_* syscalls.
Cleanup some header polution created by having seq.h in proc.h.
Reviewed by: markj, kib
Discussed with: alc
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
Differential Revision: https://reviews.freebsd.org/D13403
Add cpuctl(4) ioctl CPUCTL_EVAL_CPU_FEATURES which forces re-read of
cpu_features, cpu_features2, cpu_stdext_features, and
std_stdext_features2.
The intent is to allow the kernel to see the changes in the CPU
features after micocode update. Of course, the update is not atomic
across variables and not synchronized with readers. See the man page
warning as well.
Reviewed by: imp (previous version), jilles
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D13770
SDM editions 64 and below stated that it is enough to use MFENCe or
LFENCE to serialize x2APIC register writes. New edition 65 requires
either full serialization instruction or MFENCE;LFENCE sequence. Use
the later, FreeBSD needs serialization to ensure that writes done
before IPI request are visible to the target IPI CPU.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
(now: Interrupt_Index[15]) and assigned the previously reserved bits
55:48 (Interrupt_Index[14:0] goes into 63:49 while Destination Field
used 63:56 and bit 48 now is Interrupt_Format) in the IO redirection
tables (see the VT-d specification, "5.1.5.1 I/OxAPIC Programming").
Thus, when not using interrupt remapping, ensure that all previously
reserved bits in the high part of the RTEs are zero instead of doing
a read-modify-write for their Destination Field bits only.
Otherwise, on machines based on Apollo Lake and its derivatives such
as Denverton, typically some of the previously preserved bits remain
set after boot when not employing interrupt remapping. The result is
that INTx interrupts are not getting delivered.
Note: With an AMD IOMMU, interrupt remapping apparently bypasses the
IO APIC altogether.
Submitted by: loos (modulo comment)
Reviewed by: jhb (modulo comment)
platform divergence.
Only architectures which pass arguments in registers (mips)
and platforms which use really weird compilers (any?) would
need to augment the contents of <sys/_stdarg.h>
Convert x86, arm and arm64 architectures to use <sys/_stdarg.h>
being removed from GENERIC in 12. Always print PNP info for ISA when
it exists: it doesn't depend on ISAPNP. Add PNP ID to orm and vga to
prevent us from warning about them since those devices aren't being
removed from GENERIC. PNP devices will be removed from GENERIC too,
but they will be automatically loaded, so need no warning. We don't
warn for non-GENERIC kernels because people running them are presumed
to know what they are doing.
MFC After: 2 weeks
restart_cpus() worked well enough by accident. Before this set of fixes,
resume_cpus() used the same cpuset (started_cpus, meaning CPUs directed to
restart) as restart_cpus(). resume_cpus() waited for the wrong cpuset
(stopped_cpus) to become empty, but since mixtures of stopped and suspended
CPUs are not close to working, stopped_cpus must be empty when resuming so
the wait is null -- restart_cpus just allows the other CPUs to restart and
returns without waiting.
Fix resume_cpus() to wait on a non-wrong cpuset for the ACPI case, and
add further kludges to try to keep it working for the XEN case. It
was only used for XEN. It waited on suspended_cpus. This works for
XEN. However, for ACPI, resuming is a 2-step process. ACPI has already
woken up the other CPUs and removed them from suspended_cpus. This
fix records the move by putting them in a new cpuset resuming_cpus.
Waiting on suspended_cpus would give the same null wait as waiting on
stopped_cpus. Wait on resuming_cpus instead.
Add a cpuset toresume_cpus to map the CPUs being told to resume to keep
this separate from the cpuset started_cpus for mapping the CPUs being told
to restart. Mixtures of stopped and suspended/resuming CPUs are still far
from working. Describe new and some old cpusets in comments.
Add further kludges to cpususpend_handler() to try to avoid breaking it
for XEN. XEN doesn't use resumectx(), so it doesn't use the second
return path for savectx(), and it goes from the suspended state directly
to the restarted state, while ACPI resume goes through the resuming state.
Enter the resuming state early for all cases so that resume_cpus can test
for being in this state and not have to worry about the intermediate
!suspended state for ACPI only.
Reviewed by: kib
it by a transient double mapping for the one instruction in ACPI wakeup
where it is needed (and for many surrounding instructions in ACPI resume).
Invalidate the TLB as soon as convenient after undoing the transient
mapping. ACPI resume already has the strict ordering needed for this.
This fixes the non-trapping of null pointers and other garbage pointers
below NBPDR (except transiently). NBPDR is quite large (4MB, or 2MB for
PAE).
This fixes spurious traps at the first instruction in VM86 bioscalls.
The traps are for transiently missing read permission in the first
VM86 page (physical page 0) which was just written to at KERNBASE in
the kernel. The mechanism is unknown (it is not simply PG_G).
locore uses a similar but larger transient double mapping and needs
it for 2 instructions instead of 1. Unmap the first PDE in it after
the 2 instructions to detect most garbage pointers while bootstrapping.
pmap_bootstrap() finishes the unmapping.
Remove the avoidance of the double mapping for a recently fixed special
case. ACPI resume could use this avoidance (made non-special) to avoid
any problems with the transient double mapping, but no such problems
are known.
Update comments in locore. Many were for old versions of FreeBSD which
tried to map low memory r/o except for special cases, or might have
allowed access to low memory via physical offsets. Now all kernel
maps are r/w, and removal of of the double map disallows use of physical
offsets again.
turn it off by default. It is very inefficient to verify current P-state of
each core, especially for CPUs with many cores. When multiple commands are
requested to the same power domain before completion of pending transitions,
the last command is executed according to the manual. Because requests are
serialized by the caller, all cores will receive the same command for each
call. Do not call sched_bind() and sched_unbind(). It is redundant because
the caller does it anyway.
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
Mainly focus on files that use BSD 3-Clause license.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
Initially, only tag files that use BSD 4-Clause "Original" license.
RelNotes: yes
Differential Revision: https://reviews.freebsd.org/D13133
It is for console presented at 2001 and featuring Pentium III
processor. Even if any of them are still alive and run FreeBSD, we do
not have any sign of life from their users. While removing another
dozens of #ifdefs from the i386 sources reduces the aversion from
looking at the code and improves the platform vitality.
Reviewed by: cem, pfg, rink (XBOX support author)
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D13016
Also keep the calculated vm_page_alloc_contig() flags in the variable
to not re-evaluate it on the loop iteration.
Noted by: alc
Sponsored by: The FreeBSD Foundation
similar to the kernel memory allocator.
This simplifies NUMA allocation because the domain will be known at wait
time and races between failure and sleeping are eliminated. This also
reduces boilerplate code and simplifies callers.
A wait primitive is supplied for uma zones for similar reasons. This
eliminates some non-specific VM_WAIT calls in favor of more explicit
sleeps that may be satisfied without new pages.
Reviewed by: alc, kib, markj
Tested by: pho
Sponsored by: Netflix, Dell/EMC Isilon
- allocate value for new AT_HWCAP2 auxiliary vector on all platforms.
- expand 'struct sysentvec' by new 'u_long *sv_hwcap2', in exactly
same way as for AT_HWCAP.
MFC after: 1 month
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D12699
When it was added in r314636, AMD Thresholding was hardcoded to only
bank 4 (Northbridge) for some reason. However, even on family 10h the
MCAx_MISC register Valid/Present bits determine whether thresholding is
supported on that bank.
Expand thresholding support to monitor all monitorable banks. This
simplifies some of the logic and makes it more consistent with our Intel
CMCI support.
Reviewed by: markj (earlier version)
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D12321
A new 'u_long *sv_hwcap' field is added to 'struct sysentvec'. A
process ABI can set this field to point to a value holding a mask of
architecture-specific CPU feature flags. If an ABI does not wish to
supply AT_HWCAP to processes the field can be left as NULL.
The support code for AT_EHDRFLAGS was already present on all systems,
just the #define was not present. This is a step towards unifying the
AT_* constants across platforms.
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D12290
