is useless for threaded programs, multiple threads can not share same
stack.
The alternative signal stack is private for thread, no lock is needed,
the orignal P_ALTSTACK is now moved into td_pflags and renamed to
TDP_ALTSTACK.
For single thread or Linux clone() based threaded program, there is no
semantic changed, because those programs only have one kernel thread
in every process.
Reviewed by: deischen, dfr
eventually be passed an async. context as well as a syscall
context.
While here, fix a serious bug in that if the trapframe is a
syscall frame, but we're restoring an async context, we need
to clear the FRAME_SYSCALL flag so that we leave the kernel
via exception_restore.
The split-up code is derived from the ia64 code originally.
Note that I have only compile-tested this, not actually run-tested it.
The ia64 side of the force is missing some significant chunks of signal
delivery code.
Not all transfers between kernel and user space are byte oriented
and thus alignment safe. Especially fuword*() and suword*() are
sensitive to alignment but in general more optimal than block copies.
By catching the misalignment trap we avoid pessimizing the common
case of properly aligned memory accesses which we would do if we
were to use byte copies or adding tests for proper alignment.
Note that the expectation that the kernel produces aligned pointers
is unchanged. This change therefore relates to possible unaligned
pointers generated in userland.
as these ioctl's aren't MD. This also means they are installed in
/usr/include/dev/bktr now. Also provide compatability wrappers for
where these headers lived in 4.x.
flags. We now create asynchronous contexts or syscall contexts only.
Syscall contexts differ from the minimal ABI dictated contexts by
having the scratch registers saved and restored because that's where
we keep the syscall arguments and syscall return values.
Since this change affects KSE, have it use kse_switchin(2) for the
"new" syscall context.
very early (SI_SUB_TUNABLES - 1) and is responsible for setting mp_maxid.
cpu_mp_probe() is now called at SI_SUB_CPU and determines if SMP is
actually present and sets mp_ncpus and all_cpus. Splitting these up
allows an architecture to probe CPUs later than SI_SUB_TUNABLES by just
setting mp_maxid to MAXCPU in cpu_mp_setmaxid(). This could allow the
CPU probing code to live in a module, for example, since modules
sysinit's in modules cannot be invoked prior to SI_SUB_KLD. This is
needed to re-enable the ACPI module on i386.
- For the alpha SMP probing code, use LOCATE_PCS() instead of duplicating
its contents in a few places. Also, add a smp_cpu_enabled() function
to avoid duplicating some code. There is room for further code
reduction later since much of this code is also present in cpu_mp_start().
- All archs besides i386 still set mp_maxid to the same values they set it
to before this change. i386 now sets mp_maxid to MAXCPU.
Tested on: alpha, amd64, i386, ia64, sparc64
Approved by: re (scottl)
on SMP systems has a chance of working. This was a loose end of the
implementation of the ACPI Cx idle states. Since our logical CPU Id
is the ACPI processor Id, we do not need to jump through hoops to
obtain it.
Approved: re@ (jhb)
physical mapping.
- Move the sf_buf API to its own header file; make struct sf_buf's
definition machine dependent. In this commit, we remove an
unnecessary field from struct sf_buf on the alpha, amd64, and ia64.
Ultimately, we may eliminate struct sf_buf on those architecures
except as an opaque pointer that references a vm page.
important change is in cpu_switch() where we disable the high FP
registers for the thread that we switch-out if the CPU currently
has its high FP registers. This avoids that the high FP registers
remain enabled for the thread even when the CPU has unloaded them
or the thread migrated to another processor.
Likewise, when we switch-in a thread of that has its high FP
registers on the CPU, we enable them. This avoids an otherwise
harmless, but unnecessary trap to have them enabled.
The code that handles the disabled high FP trap (in trap()) has
been turned into a critical section for the most part to avoid
being preempted. If there's a race, we bail out and have the
processor trap again if necessary.
Avoid using the generic ia64_highfp_save() function when the
context is predictable. The function adds unnecessary overhead.
Don't use ia64_highfp_load() for the same reason. The function
is now unused and can be removed.
These changes make the lazy context switching of the high FP
registers in an UP kernel functional.
that we currently do not keep track of whether the thread has
actually used the high FP registers before. If not, we should
not save them in the context which automaticly means that we
also would not restore them from the context. For now, do it
unconditionally so that we can reach functional completeness.
functions switched to using {g|s}et_mcontext(). The problem is that
sigreturn(), being a syscall, can be given an async. context (i.e.
one corresponding to an interrupt or trap). When this happens, we
try to return to user mode via epc_syscall_return with a trapframe
that can only be used to return to user mode via exception_restore.
To fix this, we check the frame's flags immediately prior to
epc_syscall_return and branch to exception_restore for non-syscall
frames. Modify the assertion in set_mcontext() to check that if
there's a mismatch, it's because of sigreturn().
Only update them in the newly created context to reflect the state
after copying the dirty registers onto the user stack. If we were to
update the trapframe, we lose the state at entry into the kernel. We
may need that after we create the context, such as for KSE upcalls.
We have to update the trapframe after writing the dirty registers to
the user stack for signal delivery to work. But this is best done in
sendsig() itself where it applies, not in get_mcontext() where it's
done unconditionally.
use set_mcontext() to restore the context in sigreturn(). Since we
put the syscall number and the syscall arguments in the trapframe
(we don't save the scratch registers for syscalls, which allows us
to reuse the space to our advantage), create a MD specific flag so
that we save the scratch registers even for syscalls. We would not
be able to restart a syscall otherwise.
The signal trampoline does not need to flush the regiters anymore,
because get_mcontext() already handles that. In fact, if we set up
the context correctly, we do not need to have a trampoline at all.
This change however only minimally changes the trampoline code. In
follow-up commits this can be further optimized.
Note that normally we preserve cfm and iip in the trapframe created
by the EPC syscall path when we restore a context in set_mcontext()
because those fields are not normally set for a synchronuous context.
The kernel puts the return address and frame info of the syscall
stub in there. By preserving these fields we hide this detail from
userland which allows us to use setcontext(2) for user created
contexts. However, sigreturn() is commonly called from the trampoline,
which means that if we preserve cfm and iip in all cases, we would
return to the trampoline after the sigreturn(), which means we hit
the safety net: we call exit(2). So, we do not preserve cfm and iip
when we have a synchronous context that also has scratch registers
(the uncommon context created by sendsig() only), under the assumption
that if such a context is created in userland, something special is
going on and the use of cfm and iip is then just another quirk. All
this is invisible in the common case.
Since all callers either passed 0 or 1 for clear_ret, define bit 0 in
the flags for use as clear_ret. Reserve bits 1, 2 and 3 for use by MI
code for possible (but unlikely) future use. The remaining bits are for
use by MD code.
This change is triggered by a need on ia64 to have another knob for
get_mcontext().
are zx1 based machines and they don't particularly like it when we
poke at them with PC legacy code. The atkbd and psm devices were
disabled in the hints file so that one could enable them on machines
that support legacy devices, but that's not really something you can
expect from a first-time installer. This still leaves syscons (sc)
and the vga device, which were enabled by default and wrecking havoc
anyway. We could disable them by default like the atkbd and psm
devices, but there's really no point in pretending we're in a better
shape that way.
sure we handle stacked registers properly by taking into account
that:
1. bspstore points after the frame (due to cover),
2. we need to adjust for intermediate NaT collections.
cr.isr sanity check. We actually encounter insanities, which very
likely means that the insanity check itself is insane. Remove an empty
comment while I'm at it.
An example of useless is bios.h. An example of wrong is msdos.h (due
to the use of long for 32-bit fields).
display.h cannot be removed because it's used by syscons. That header
however has no platform dependency and shouldn't really be here.
Removal if these headers may cause build failures in the ports tree.
It's the ports that need fixing in that case.
Tested with: buildworld, LINT
the RNAT bit index constant. The net effect of this is that there's
no discontinuity WRT NaT collections which greatly simplifies certain
operations. The cost of this is that there can be up to 504 bytes of
unused stack between the true base of the kernel stack and the start
of the RSE backing store. The cost of adjusting the backing store
pointer to keep the RNAT bit index constant, for each kernel entry,
is negligible.
The primary reasons for this change are:
1. Asynchronuous contexts in KSE processes have the disadvantage of
having to copy the dirty registers from the kernel stack onto the
user stack. The implementation we had so far copied the registers
one at a time without calculating NaT collection values. A process
that used speculation would not work. Now that the RNAT bit index
is constant, we can block-copy the registers from the kernel stack
to the user stack without having to worry about NaT collections.
They will be in the right place on the user stack.
2. The ndirty field in the trapframe is now also usable in userland.
This was previously not the case because ndirty also includes the
space occupied by NaT collections. The value could be off by 8,
depending on the discontinuity. Now that the RNAT bit index is
contants, we have exactly the same number of NaT collection points
on the kernel stack as we would have had on the user stack if we
didn't switch backing stores.
3. Debuggers and other applications that use ptrace(2) can now copy
the dirty registers from the kernel stack (using ptrace(2)) and
copy them whereever they want them (onto the user stack of the
inferior as might be the case for gdb) without having to worry
about NaT collections in the same way the kernel doesn't have to
worry about them.
There's a second order effect caused by the randomization of the
base of the backing store, for it depends on the number of dirty
registers the processor happened to have at the time of entry into
the kernel. The second order effect is that the RSE will have a
better cache utilization as compared to having the backing store
always aligned at page boundaries. This has not been measured and
may be in practice only minimally beneficial, if at all measurable.
license. Only clause 3 has been revoked. Restore the fourth clause
as clause 3.
Pointed out by: das@
Remove my name as a copyright holder since I don't use a BSD license
compatible or comparable to the UCB license. I choose not to add a
complete second license for my work for aesthetic reasons, nor to
replace the UCB license on grounds of rewriting more than 90% of the
source files. The rewrite can also be seen as an enhancement and since
the files were practically empty, it's rather trivial to have changed
90% of the files.
added for XFree86. There are 2 reasons for doing this with sysarch():
1. The memory mapped I/O space is not at a fixed physical address. An
application has to use some interface to get the base address. It
gets worse if the machine has multiple memory mapped I/O spaces.
2. Access to the memory mapped I/O space needs to happen through a
translation that is flagged as uncachable. There's no interface
that allows a process to do uncached memory I/O, other than though
/dev/mem (possibly).
So, until we either disallow direct access to I/O or bus space from
userland or have a better way of doing this, sysarch() has the least
negative impact on existing interfaces.
