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.
overlapping TR/TC entries (which results in a machine check). Note
that we don't look at the size of the memory descriptor, because
it doesn't guarantee non-overlap.
With this change, a UP kernel could boot on a Intel Tiger4 machine
with the following options:
options LOG2_ID_PAGE_SIZE=26 # 64M
options LOG2_PAGE_SIZE=14 # 16K
Approved by: marcel
we had were bogus.
While here, reassign the copyright to the Project. There's nothing
in this files that originates from NetBSD, especially now that the
FreeBSD/alpha bits have been removed, but even then the amount of
inherited code that we actually used was nil.
mcontext_t for the register values. Currently only ld8 and ldfd
instructions are handled as those are the ones we need now (a
misaligned ld8 occurs 4 times in ntpd(8) and a misaligned ldfd
occurs once in mozilla 1.4 and 1.5). Other instructions are added
when needed.
at the first address and spills it to the second address. This
allows unaligned_fixup() to update the context of the process in
a way that assures proper rounding.
Similar functions for single-and extended-precision are added when
needed.
in that it provides an abstract (intermediate) representation for
instructions. This significantly improves working with instructions
such as emulation of instructions that are not implemented by the
hardware (e.g. long branch) or enhancing implemented instructions
(e.g. handling of misaligned memory accesses). Not to mention that
it's much easier to print instructions.
Functions are included that provide a textual representation for
opcodes, completers and operands.
The disassembler supports all ia64 instructions defined by revision
2.1 of the SDM (Oct 2002).
by libguile that needs to know the base of the RSE backing store. We
currently do not export the fixed address to userland by means of a
sysctl so user code needs to hardcode it for now. This will be revisited
later.
The RSE backing store is now at the bottom of region 4. The memory stack
is at the top of region 4. This means that the whole region is usable
for the stacks, giving a 61-bit stack space.
Port: lang/guile (depended of x11/gnome2)
halt state that minimizes power consumption while still preserving
cache and TLB coherency. Halting the processor is not conditional at
this time. Tested with UP and SMP kernels.
from UWX_REG_MUMBLE to UWX_REG_AR_MUMBLE. Compatibility defines are
present in libuwx. Change the names here so that we don't depend on
compatibility defines.
Note that there's now an UWX_REG_PFS and an UWX_REG_AR_PFS and the
former is not a compatibility define for the latter AFAICT. Change
to UWX_REG_AR_PFS as that seems to be the one we need to handle.
A small helper function pmap_is_prefaultable() is added. This function
encapsulate the few lines of pmap_prefault() that actually vary from
machine to machine. Note: pmap_is_prefaultable() and pmap_mincore() have
much in common. Going forward, it's worth considering their merger.
frame marker) and the syscall stub frame info in the trap frame.
Previously we stored the stub frame info in (rp,pfs) and the
caller frame info in (iip,cfm). This ends up being suboptimal
for the following reasons:
1. When we create a new context, such as for an execve(2), we had
to set the (rp,pfs) pair for the entry point when using the
syscall path out of the kernel but we need to set the (iip,cfm)
pair when we take the interrupt way out. This is mostly just
an inconsistency from the kernel's point of view, but an ugly
irregularity from gdb(1)'s point of view.
2. The getcontext(2) and setcontext(2) syscalls had to swap the
(rp,pfs) and (iip,cfm) pairs to make the context compatible
with one created purely in userland.
Swapping the (rp,pfs) and (iip,cfm) pairs is visible to signal
handlers that actually peek at the mcontext_t and to gdb(1).
Since this change is made for gdb(1) and we don't care about
signal handlers that peek at the mcontext_t because we're still
a tier 2 platform, this ABI breakage is academic at this moment
in time.
Note that there was no real reason to save the caller frame info
in (iip,cfm) and the stub frame info in (rp,pfs).
about because we're still tier 2 and our current compiler, as well
as future compilers will not support varargs. This is mostly a
no-op in practice, because <sys/varargs.h> should already cause
compile failures.
systems where the data/stack/etc limits are too big for a 32 bit process.
Move the 5 or so identical instances of ELF_RTLD_ADDR() into imgact_elf.c.
Supply an ia32_fixlimits function. Export the clip/default values to
sysctl under the compat.ia32 heirarchy.
Have mmap(0, ...) respect the current p->p_limits[RLIMIT_DATA].rlim_max
value rather than the sysctl tweakable variable. This allows mmap to
place mappings at sensible locations when limits have been reduced.
Have the imgact_elf.c ld-elf.so.1 placement algorithm use the same
method as mmap(0, ...) now does.
Note that we cannot remove all references to the sysctl tweakable
maxdsiz etc variables because /etc/login.conf specifies a datasize
of 'unlimited'. And that causes exec etc to fail since it can no
longer find space to mmap things.
not guaranteed that the RSE writes the NaT collection immediately,
sort of atomically, to the backing store when it writes the register
immediately prior to the NaT collection point. This means that we
cannot assume that the low 9 bits of the backingstore pointer do not
point to the NaT collection. This is rather a surprise and I don't
know at this time if it's a bug in the Merced or that it's actually
a valid condition of the architecture. A quick scan over the sources
does not indicate that we depend on the false assumption elsewhere,
but it's something to keep in mind.
The fix is to write the saved contents of the ar.rnat register to
the backingstore prior to entering the loop that copies the dirty
registers from the kernel stack to the user stack.
functions reference UMA internals from <vm/uma_int.h>, which makes
them highly unwanted in non-UMA specific files.
While here, prune the includes in pmap.c and use __FBSDID(). Move
the includes above the descriptive comment.
The copyright of uma_machdep.c is assigned to the project and can
be reassigned to the foundation if and when when such is preferrable.
restart instruction bits in the PSR. As such, we were returning
from interrupt to the instruction in the bundle that caused us
to enter the kernel, only now we're returning to a completely
different bundle.
While close here: add two KASSERTs to make sure that we restore
sync contexts only when entered the kernel through a syscall and
restore an async context only when entered the kernel through an
interrupt, trap or fault.
While not exactly here, but close enough: use suword64() when we
copy the dirty registers from the kernel stack to the user stack.
The code was intended to be be replaced shortly after being added,
but that was a couple of weeks ago. I might as well avoid that it
is a source for panics until it's replaced.
