of this micro-optimization occurs when we call pmap_enter() to wire an
already mapped page. Because of the micro-optimization, we fail to
mark the PTE as wired. Later, on teardown of the address space,
pmap_remove_pages() destroys the PTE before vm_fault_unwire() has
unwired the page. (pmap_remove_pages() is not supposed to destroy
wired PTEs. They are destroyed by a later call to pmap_remove().)
Thus, the page becomes lost.
Note: The page is not lost if the application called munlock(2), only
if it relies on teardown of the address space to unwire its pages.
For the historically inclined, this bug was introduced by a
megacommit, revision 1.182, roughly six years ago.
Leak observed by: green@ and dillon independently
Patch submitted by: dillon at backplane dot com
Reviewed by: tegge@
MFC after: 1 week
gmon and struct gmonhdr was originally just to represent the kernel
(profiling) clock frequency and it remains poorly suited to representing
the frequencies of fast counters like the TSC. It broke a year or two
ago. This quick fix keeps it working for another year or month or two
until TSC frequencies can exceed 2^32, by dividing the frequency by 2.
Dividing the frequency by 4 would work for a little longer but would
lose a little too much precision.
ordinary functions, essentially by backing out half of rev.1.115 of
amd64/exception.S. The handlers must be between certain labels for
the purposes of profiling, and this was broken by scattering them in
separately compiled .S files, especially for ordinary functions that
ended up between the labels. Merge the files by #including them as
before, except with different pathnames and better comments and
organization. Changes to the scattered files are minimal -- just
move the labels to the file that does the #includes.
This also partly fixes profiling of IPIs -- all IPI handlers are now
correctly classified as interrupt handlers, but many are still missing
mcount calls.
- perfmon headers must be avoided until perfmon is supported.
- all call-used registers including return registers must be preserved
by .mcount(), etc., not quite as in profile.h. __cyg_profile_func_*()
don't require this, but they are (mis)implemented as aliases for
.mcount(), etc. so they preserve the registers.
- i386 ifdefs related to perfmon have not been adjusted yet.
amd64 as necessary. This is routine, except:
- the FAKE_MCOUNT($bintr) in doreti was missing the '$'. This gave a
a garbage address made up of padding bytes (with the nop byte 0x90 as
the MSB) instead of the intended address of bintr. This accidentally
worked on i386's because (0x90 << 24) is close enough to bintr, but
it doesn't work on amd64's because (0x90 << 56) is much further away
from bintr.
- the FAKE_MCOUNT($btrap) in calltrap was similarly broken. It hasn't
been needed since FreeBSD-1, so just delete it.
and high resolution profiling of interrupt handlers. The adjustments
are routine once the magic stack offset 13*4 is decoded to be TF_RIP
(there were originally more types of stack frames so using TF_EIP for
one of them wouldn't have been much simpler).
Removed garbage comments attached to some of the FAKE_MCOUNT()s.
that the usual macro for "ret" hides the detail of calling .mexitcount
before returning.
Fixed missing call to .mexitcount in lgdt(). This was missing on
i386's, mainly because lgdt() uses lret[q] insted of ret. This is
very unimportant since lgdt() is not (normally?) called until after
profiling is initialized.
and improved some comments). Also, made the documented {f,s}uword()
functions the standard entry points and the undocumented {f,s}uword64()
functions alternative entry points, like {f,s}uword32() for i386's. The
bitrot in the comments was a little larger here -- there are new undocumented
32-bit sub-word functions, not just renaming of 16-bit functions from
documented ones to undocumented ones.
to <sys/gmon.h>. Cleaned them up a little by not attempting to ifdef
for incomplete and out of date support for GUPROF in userland, as in
the sparc64 version.
different context support for 32 vs 64 bit processes. This simply omits
the save/restore of the segment selector registers for non 32 bit
processes. This avoids the rdmsr/rwmsr juggling when restoring %gs
clobbers the kernel msr that holds the gsbase.
However, I suspect it might be better to conditionally do this at
user<->kernel transition where we wouldn't need to do the juggling in the
first place. Or have per-thread extended context save/restore hooks.
to help the AMD cpus (which have a hardware tlb flush filter). I held
off to see what the 64 bit Intel cpus did, but it doesn't seem to help
much there either. Oh well, store it in the Attic.
elf_reloc() backends for two reasons. First, to support the possibility
of there being two elf linkers in the kernel (eg: amd64), and second, to
pass the relocbase explicitly (for relocating .o format kld files).
individual asm versions. The global lock is shared between the BIOS and
OS and thus cannot use our mutexes. It is defined in section 5.2.9.1 of
the ACPI specification.
Reviewed by: marcel, bde, jhb
register controlled the trigger mode and polarity of EISA interrupts.
However, it appears that most (all?) PCI systems use the ELCR to manage
the trigger mode and polarity of ISA interrupts as well since ISA IRQs used
to route PCI interrupts need to be level triggered with active low
polarity. We check to see if the ELCR exists by sanity checking the value
we get back ensuring that IRQS 0 (8254), 1 (atkbd), 2 (the link from the
slave PIC), and 8 (RTC) are all clear indicating edge trigger and active
high polarity.
This mini-driver will be used by the atpic driver to manage the trigger and
polarity of ISA IRQs. Also, the mptable parsing code will use this mini
driver rather than examining the ELCR directly.
