kernel's VA regions, we cannot limit the use of break-based
syscalls to user mode only. The signal trampolines are in the
gateway page, which is mapped into the process address space in
region 5 and thus is kernel space.
We don't special case the gateway page here. Allow break-based
syscalls from anywhere in the kernel VA space.
Approved by: re@ (blanket)
to userland with interrupts disabled until we restore PSR. However,
it has been observed that interrupts do actually happen before they
are enabled again. This is a bit surprising and I don't know yet
what's going on exactly. Nevertheless, the code was not crafted
carefully enough to allow interrupts to happen and we could
clobber the kernel stack of another thread when interrupts did
happen.
This is what happens: we restore the (memory) stack pointer (sp)
and the register stack base prior to restoring ar.k6 and ar.k7.
This is not a problem if interrupts don't happen between setting
sp/ar.bspstore and ar.k6/ar.k7. Alas, interrupts can happen.
Since sp/ar.bspstore already point to the userland stacks, we
need to switch to the kernel stack in interrupt. However, ar.k6
and ar.k7 have not been set, which means that we were switching
to some unrelated kstack and happily clobbered the trapframe
present there if the thread to which the kstack belonged was
in kernel mode or otherwise we could have our trapframe clobbered
if that other thread enters the kernel. Nasty either way.
We now carefully restore ar.k6 prior to restoring ar.bspstore and
likewise for ar.k7 and sp. All we need is the guarantee that an
interrupt does not clobber ar.k6 or ar.k7 before we're back in
userland. That has been achieved by restoring ar.k6/ar.k7
unconditionally (see exception.s)
While here, remove the disabling of interrupts on EPC entry. It
was added as a way to "resolve" the crashes until it was understood
what was going on. I think I achieved the latter, so we can remove
the patch. Note that setting up a trapframe with interrupts
enabled has it's own share of corner cases, but it's better to
properly fixed those than to keep a mostly wrong patch around
because we're afraid to remove it...
Approved by: re@ (blanket)
PSR only to achieve setting PSR.i back to it's previous value. It
makes it impossible to change any of the 30+ other unrelated bits
when done between intr_disable() and intr_restore(). That's bad.
Instead have intr_disable() return 1 when interrupts were previously
enabled and 0 otherwise and only enable interrupts in intr_restore()
when given a non-0 value.
This change specifically disallows using intr_restore() to disable
interrupts. The reason is simple: interrupts only need to be restored
after they are being disabled, which means that intr_restore() is
called with interrupts disabled and we only need to enable them if
they were previously enabled.
This change does not fix any bugs, other than that it bugged me...
Approved by: re@ (blanket)
and user mode. We need to take into account that the EPC syscall path
introduces a grey area in which one can argue either way, including a
third: neither.
We now use the region in which the IP address lies. Regions 5, 6 and 7
are kernel VA regions and if the IP lies any any of those regions we
assume we're in kernel mode. Hence, we can be in kernel mode even if
we're not on the kernel stack and/or have user privileges. There're
gremlins living in the twilight zone :-)
For the EPC syscall path this particularly means that the process
leaves user mode the moment it calls into the gateway page. This
makes the most sense because from a process' point of view the call
represents a request to the kernel for some service and that service
has been performed if the call returns. With the metric we picked,
this also means that we're back in user mode IFF the call returns.
Approved by: re@ (blanket)
when returning from an interrupt. Both registers are used on interrupt
to switch to the right kernel stack, but other than that they are not
used. This means we only have to make sure they contain proper values
while in user mode. As such, we conditionally restored these registers
based on whether we returned to userland or not. A nice property of
conditionally restoring ar.k6 and ar.k7 is that it introduces two
invariants: ar.k6 always points to the bottom of the kernel stack and
ar.k7 always points to the top of the kernel stack (immediately below
the PCB we have there).
However, the EPC syscall path introduces an irregularity: there's no
"thin red line" between user and kernel. There's a grey area that's a
couple of instructions wide. Any interruption in that grey area is
bound to see an inconsistent state. One such state is that we're in
kernel space for all practical purposes, but we still need to have
ar.k6 and ar.k7 restored as if we're in userland.
Thus: restore ar.k6 and ar.k7 unconditionally at the cost of losing
a valuable invariant. Both registers now hold the extend of the
usable portion of the kernel stack at any interrupt nesting, which
when in userland mean the bottom and the top of the kstack.
On alpha, PAL is involved in context management and after wiring
the CPU (in alpha_init()) a context switch was performed to tell
PAL about the context. This was bogusly brought over to ia64
where it introduced bugs, because we restored the context from
a mostly uninitialized PCB.
The cleanup constitutes:
o Remove the unused arguments from ia64_init().
o Don't return from ia64_init(), but instead call mi_startup()
directly. This reduces the amount of muckery in assembly and
also allows for the next bullet:
o Save our currect context prior to calling mi_startup(). The
reason for this is that many threads are created from thread0
by cloning the PCB. By saving our context in the PCB, we have
something sane to clone. It also ensures that a cloned thread
that does not alter the context in any way will return to
the saved context, where we're ready for the eventuality with
a nice, user unfriendly panic().
The cleanup fixes at least the following bugs:
o Entering mi_startup() with the RSE in enforced lazy mode.
o Re-execution of ia64_init() in certain "lab" conditions.
While here, add proper unwind directives to __start() so that
the unwind knows it has reached the bottom of the (call) stack.
Approved by: re@ (blanket)
When interrupting a kernel context, we don't need to switch stacks
(memory nor register). As such, we were also not restoring the
register stack pointer (ar.bspstore). This, however, fails to be
valid in 1 situation: when we interrupt a register stack switch as
is being done in restorectx(). The problem is that restorectx()
needs to have ar.bsp == ar.bspstore before it can assign the new
value to ar.bspstore. This is achieved by doing a loadrs prior to
assigning to ar.bspstore. If we take an interrupt in between the
loadrs and the assignment and we don't make sure we restore the
ar.bspstore prior to returning from the interrupt, we switch
stacks with possibly non-zero dirty registers, which means that
the new frame pointer (ar.bsp) will be invalid.
So, instead of jumping over the restoration of the register frame
pointer and related registers, we conditionalize it based on whether
we return to kernel context or user context. A future performance
tweak is possible by only restoring ar.bspstore when returning to
kernel mode *and* when the RSE is in enforced lazy mode. One cannot
assume ar.bsp == ar.bspstore if the RSE is not in enforced lazy mode
anyway.
While here (well, not quite) don't unconditionally assign to
ar.bspstore in exception_save. Only do that when we actually switch
stacks. It can only harm us to do it unconditionally.
Approved by: re@ (blanket)
register stack. There's nothing really wrong with flushing before
putting the RSE in enforced lazy mode, provided you don't depend on
ar.bspstore being equal to ar.bsp when the RSE has been put in
enforced lazy more. The small window between the flush and setting
the RSE may be sufficient to have the RSE eagerly increase the dirty
region (and hence cause ar.bspstore != ar.bsp) or have an interrupt
that may even get the laziest RSE to do something.
Anyway: we don't depend on ar.bspstore being equal to ar.bsp, so
nothing was and is broken. But the code was non-intuitive and
easily confuses. This is a source of future bugs.
Note: the advantage of not depending on ar.bspstore is that there's
some recilience against an interrupted flushrs. Clobbering is limited
to stacked register contents only, not to RSE address clobbering.
Approved: re@ (blanket)
failt and data access fault install the PTE in question into
the VHPT table. However, a post-increment was missing and we
wrote the raw PTE data into the pagesize/access key field.
This leaves a corrupt VHPT entry.
o While here, remove the explicit cache purge. Insertion into
the translation implicitly purges any overlapping entries.
o Make sure there's a cycle break between the itc and the rfi.
o Whitespace fixes.
a mutex. The only volatile chain operations are insertion and deletion
but since updating an existing PTE also updates the VHPT entry itself,
and we have the VHPT mutex in both other cases, we also lock when we
update an existing PTE even though no chain operation is involved.
Note that we perform the insertion and deletion careful enough that
we don't need to lock traversals. If we need to lock traversals, we
also need to lock from the exception handler, which we can't without
creating a trapframe.
We're now able to withstand a -j8 buildworld. More work is needed to
withstand Murphy fields. In other words: we still have a bogon...
Approved by: re@ (blanket)
- Fix visibilty test for LONG_BIT and WORD_BIT. `#if defined(__FOO_VISIBLE)'
is alays wrong because __FOO_VISIBLE is always defined (to 0 for
invisibility).
sys/<arch>/include/limits.h
sys/<arch>/include/_limits.h:
- Style fixes.
Submitted by: bde
Reviewed by: bsdmike
Approved by: re (scottl)
interrupted while writing into the VHPT table. While here, make sure
memory accesses a properly ordered. Tag invalidation must happen
first so that the hardware VHPT walker will not be able to match
this entry while we're updating it and we have to make sure the new
new tag gets written only after the PTE is completely updated.
Approved by: re (blanket)
previously committed cleared pcb_current_pmap prior to changing
the region registers, but that was removed before committing.
Since we don't normally (at all?) pass a NULL pointer, the bug
was mostly harmless. Fix it while I'm here...
I'm here because we need to have data serialization after writing
to the region registers. Not doing so was likely the cause of the
hangs we were experiencing. General exceptions in cpu_switch may
also be caused by the lack of serialization.
Approved by: re (blanket)
switching user regions (region 0-4) with schedlock. Avoid unnecessary
recursion on schedlock by moving the core functionality to another
function (pmap_switch()) where we assert schedlock is held. Turn
pmap_install() into a wrapper that grabs schedlock. This minimizes
the number of callsites that need to be changed.
Since we already have schedlock in cpu_switch() and cpu_throw(),
have them call pmap_switch() directly. These were also the only two
calls to pmap_install() outside pmap.c, so make pmap_install() static
and remove its prototype from pmap.h
Approved by: re (blanket)
prime objectives are:
o Implement a syscall path based on the epc inststruction (see
sys/ia64/ia64/syscall.s).
o Revisit the places were we need to save and restore registers
and define those contexts in terms of the register sets (see
sys/ia64/include/_regset.h).
Secundairy objectives:
o Remove the requirement to use contigmalloc for kernel stacks.
o Better handling of the high FP registers for SMP systems.
o Switch to the new cpu_switch() and cpu_throw() semantics.
o Add a good unwinder to reconstruct contexts for the rare
cases we need to (see sys/contrib/ia64/libuwx)
Many files are affected by this change. Functionally it boils
down to:
o The EPC syscall doesn't preserve registers it does not need
to preserve and places the arguments differently on the stack.
This affects libc and truss.
o The address of the kernel page directory (kptdir) had to
be unstaticized for use by the nested TLB fault handler.
The name has been changed to ia64_kptdir to avoid conflicts.
The renaming affects libkvm.
o The trapframe only contains the special registers and the
scratch registers. For syscalls using the EPC syscall path
no scratch registers are saved. This affects all places where
the trapframe is accessed. Most notably the unaligned access
handler, the signal delivery code and the debugger.
o Context switching only partly saves the special registers
and the preserved registers. This affects cpu_switch() and
triggered the move to the new semantics, which additionally
affects cpu_throw().
o The high FP registers are either in the PCB or on some
CPU. context switching for them is done lazily. This affects
trap().
o The mcontext has room for all registers, but not all of them
have to be defined in all cases. This mostly affects signal
delivery code now. The *context syscalls are as of yet still
unimplemented.
Many details went into the removal of the requirement to use
contigmalloc for kernel stacks. The details are mostly CPU
specific and limited to exception_save() and exception_restore().
The few places where we create, destroy or switch stacks were
mostly simplified by not having to construct physical addresses
and additionally saving the virtual addresses for later use.
Besides more efficient context saving and restoring, which of
course yields a noticable speedup, this also fixes the dreaded
SMP bootup problem as a side-effect. The details of which are
still not fully understood.
This change includes all the necessary backward compatibility
code to have it handle older userland binaries that use the
break instruction for syscalls. Support for break-based syscalls
has been pessimized in favor of a clean implementation. Due to
the overall better performance of the kernel, this will still
be notived as an improvement if it's noticed at all.
Approved by: re@ (jhb)
switching to kernel_pmap. The pmap is not special enough.
o Clear the active bit on the pmap we're switching out.
o Fix some nearby style(9) bugs.
Approved by: re@
kernel_vm_end in pmap_bootstrap. Don't delay the initialization until
we need to grow the kernel VM space. This BTW happens twice before
we enter either single- or multi-user mode. Don't adjust kernel_vm_end
while growing based on whether the KPT contains a non-NULL entry. We
trust kernel_vm_end to be correct and we make sure it's still correct
after growing.
Define virtual_avail and virtual_end in terms of VM_MIN_KERNEL_ADDRESS
and VM_MAX_KERNEL_ADDRESS (resp). Don't hardcode region knowledge.
o Limit the size of the region ID map to 64KB. This gives a bitmap
that is large enough to keep track of 2^19 numbers. The minimal map
size is 32KB. The reason we limit the map size is that processor
models may have implemented a 24-bit region ID, which would give
a 2MB bitmap while the maximum number of allocations is always
less than PID_MAX*5, which is less than 2^19.
o Allocate all region IDs up-front. The slight downside of reserving
more RIDs then a process needs (3 for ia64 native and 1 for ia32)
is preferable over the call to pmap_ensure_rid() where RIDs are
allocated on demand. On SMP systems this may lead to a race
condition.
o When allocating a region ID, don't use arc4random(). We're not
interested in randomness or uniform distribution across the
spectrum. We only need uniqueness. Random numbers may easily
collide when the number of allocated RIDs is high, creating a
possibly unbounded retry rate.
The advantage of using register sets is that you don't focus on each
register seperately, but instead instroduce a level of abstraction.
This reduces the chance of errors, and also simplifies the code.
The register sers form the basis of everything register.
The sets in this file are:
struct _special
contains all of the control related registers, such as instruction
pointer and stack pointer. It also contains interrupt specific registers
like the faulting address. The set is roughly split in 3 groups. The
first contains the registers that define a context or thread. This is
the only group that the kernel needs to switch threads. The second group
contains registers needed in addition to the first group needed to switch
userland threads. This group contains the thread pointer and the FP control
register. The third group contains those registers we need for execption
handling and are used on top of the first two groups.
struct _callee_saved, struct _callee_saved_fp
These sets contain the preserved registers, including the NaT after
spilling. The general registers (including branch registers) are
seperated from the FP registers for ptrace(2).
struct _caller_saved, struct _caller_saved_fp
These sets contain the scratch registers based on SDM 2.1, This means that
both ar.csd and ar.ccd are included here, even though they contain ia32
segment register descriptions. We keep seperate NaT bits for scratch and
preserved registers, because they are never saved/restored at the same
time.
struct _high_fp
The upper 96 FP registers that can be enabled/disabled seperately on
the CPU from the lower 32 FP registers. Due to the size of this set,
we treat them specially, even though they are defined as scratch
registers.
CVS ----------------------------------------------------------------------
save and restore "sets" of registers in various places.
The restorectx and swapctx functions are used by cpu_switch()
and deal with the special registers, as well as the preserved
registers.
The *callee_saved* functions are used to save and restore the
preserved registers (integer and floating-point). They are
useful for signal delivery and ptrace support.
The save_high_fp and restore_high_fp functions are used to
"load" and "unload" to and from the CPU as part of lazy context
switching.
The ia32 specific context functions have been kept with the ia32
code.
Approved by: re@ (blanket)
on the epc instruction. The epc instruction, given the permissions
of the page in which the epc is located, allows the privilege level
to be increased with little or no overhead. The previous privilege
level is recorded in the current frame marker and is restored by
a regular (function) return.
Since the epc instruction has to live in a page with non-standard
properties, we hardwire a "gateway" page in the address space. The
address of the gateway page is exported to userland in ar.k7. This
allows us to rewire the page without breaking the ABI.
The syscall stubs in libc are regular function calls that slightly
differ from the normal runtime. The difference is mostly to simplify
the stubs themselves by by moving some of the logic to the kernel.
The libc stubs call into the gateway page (offset 0), from where the
kernel trampolines to the code that sets up a minimal trapframe and
arranges to execute from the kernel stack.
The way back is basicly the same. The kernel returns to the gateway
page, whereby privilege is dropped, and jumps back to the syscall
stub.
Only the special registers are saved in the trapframe. None of the
scratch registers are preserved and since the kernel follows the
same runtime model, none of the preserved registers are saved.
Future enhancements can include the implementation of lightweight
syscalls, where kernel functions are performed without setting up
a trapframe. Good candidates are the *context syscalls for example.
Now that there's a gateway page from which code can be executed in
a non-privileged context, we also have the ideal place to put the
signal trampolines. By moving the signal trampolines from the user
stack to the gateway page, we open up the doors to unexecutable
stacks. The gateway page contains signal trampolines for both the
"legacy" break-based syscall code and the new and improved epc-
based syscall code.
Approved: re@ (blanket)
- Move struct sigacts out of the u-area and malloc() it using the
M_SUBPROC malloc bucket.
- Add a small sigacts_*() API for managing sigacts structures: sigacts_alloc(),
sigacts_free(), sigacts_copy(), sigacts_share(), and sigacts_shared().
- Remove the p_sigignore, p_sigacts, and p_sigcatch macros.
- Add a mutex to struct sigacts that protects all the members of the struct.
- Add sigacts locking.
- Remove Giant from nosys(), kill(), killpg(), and kern_sigaction() now
that sigacts is locked.
- Several in-kernel functions such as psignal(), tdsignal(), trapsignal(),
and thread_stopped() are now MP safe.
Reviewed by: arch@
Approved by: re (rwatson)
Remove DBL_DIG, DBL_MIN, DBL_MAX and their FLT_ counterparts, they
were marked for deprecation ever since SUSv1 at least.
Only define ULLONG_MIN/MAX and LLONG_MAX if long long type is
supported.
Restore a lost comment in MI _limits.h file and remove it from
sys/limits.h where it does not belong.
o do not use the in* and out* functions. These functions are used by
legacy drivers and thus must have ia32 compatible behaviour. Hence,
they need to have fences. Using these functions for newbus would
then pessimize performance.
o remove the conditional compilation of PIO and/or MEMIO support. It's
a PITA without having any significant benefit. We always support them
both. Since there are no I/O ports on ia64 (they are simulated by the
chipset by translating memory mapped I/O to predefined uncacheable
memory regions) the only difference between PIO and MEMIO is in the
address calculation. There should be enough ILP that can be exploited
here that making these computations compile-time conditional is not
worth it. We now also don't use the read* and write* functions.
o Add the missing *_8 variants. They were missing, although not missed.
It's for completeness.
o Do not add the fences that were present in the low-level support
functions here. We're using uncacheable memory, which means that
accesses are in program order. Change the barrier implementation
to not only do a memory fence, but also an acceptance fence. This
should more reliably synchronize drivers with the hardware. The
memory fence enforces ordering, but does not imply visibility (ie
the access does not necessarily have happened). This is what the
acceptance deals with.
cpufunc.h cleanup:
o Remove the low-level memory mapped I/O support functions. They are
not used. Keep the low-level I/O port access functions for legacy
drivers and add fences to ensure ia32 compatibility.
o Remove the syscons specific functions now that we have moved the
proper definitions where they belong.
o Replace the ia64_port_address() and ia64_memory_address() functions
with macros. There's a bigger change inline functions get inlined
when there aren't function callsi and the calculations are simply
enough to do it with macros.
Replace the one reference to ia64_memory address in mp_machdep.c to
use the macro.
syscall return values should be cleared. The system calls
getcontext() and swapcontext() want to return 0 on success
but these contexts can be switched to at a later time so
the return values need to be cleared in the saved register
sets. Other callers of get_mcontext() would normally want
the context without clearing the return values.
Remove the i386-specific context saving from the KSE code.
get_mcontext() is not i386-specific any more.
Fix a bad pointer in the alpha get_mcontext() code. The
context was being bcopy()'d from &td->tf_frame, but tf_frame
is itself a pointer, so the thread was being copied instead.
Spotted by jake.
Glanced at by: jake
Reviewed by: bde (months ago)
to get actual constant values. This is in preparation for machine/limits.h
retirement.
Discussed on: standards@
Submitted by: Craig Rodrigues <rodrigc@attbi.com> (*)
Modified by: kan
kern_sigprocmask() in the various binary compatibility emulators.
- Replace calls to sigsuspend(), sigaltstack(), sigaction(), and
sigprocmask() that used the stackgap with calls to the corresponding
kern_sig*() functions instead without using the stackgap.
instruction requires that a translation is present in the TC. This
may trigger a TLB miss and a subsequent call to vm_fault().
This implementation is deliberately non-inline for debugging and
profiling purposes. Partial or full inlining should eventually be
done.
Valuable insights by: jake
enum to an int and redefine the BUS_DMASYNC_* constants as
flags. This allows us to specify several operations in one
call to bus_dmamap_sync() as in NetBSD.
by allprison_mtx), a unique prison/jail identifier field, two path
fields (pr_path for reporting and pr_root vnode instance) to store
the chroot() point of each jail.
o Add jail_attach(2) to allow a process to bind to an existing jail.
o Add change_root() to perform the chroot operation on a specified
vnode.
o Generalize change_dir() to accept a vnode, and move namei() calls
to callers of change_dir().
o Add a new sysctl (security.jail.list) which is a group of
struct xprison instances that represent a snapshot of active jails.
Reviewed by: rwatson, tjr
of asserting that an mbuf has a packet header. Use it instead of hand-
rolled versions wherever applicable.
Submitted by: Hiten Pandya <hiten@unixdaemons.com>
