This is required for ISA 2.0 support, see chapter
"Zicsr", Control and Status Register (CSR) Instructions, Version 2.0
in
RISC-V Instruction Set Manual, Volume I: RISC-V User-Level ISA
When committed, the MicroBlaze RAM size was hard-coded to 16MB. This
changes the default to 256MB and sets the KCU105 BSPs to 2GB since that
is what the board has on it.
Add MicroBlaze support for libdebugger. This uses only software break
type instructions to provide self-hosted GDB debugging support for
applications since internal control of debug hardware is not possible.
Also of note, this implementation for MicroBlaze would typically use the
brki instruction for software break, but instead uses an illegal opcode
to manage software breaks as exceptions. This is due to poor interaction
with the debug hardware where the debug hardware will intercept software
breaks instead of allowing the software break vector to execute.
This updates behavior of libdebugger to handle debug exceptions in
interrupt context by temporarily removing a software breakpoint,
stepping, and then resuming afterward.
Exception handling should be enabled at all times during execution to
ensure that exceptions are not ignored which would cause further
problems. This separates use of the exception enable bit from use of the
interrupt enable bit in the machine status register so that they can be
manipulated independently.
Add a capability that allows for implementations that operate purely
using software breaks. Due to this implementation method, software
breaks must not be restored until just before returning control to the
thread itself and will be handled by the implementation through thread
switch and interrupt hooks.
It is possible to remove software breaks without actually restoring the
original instruction to memory. When this happens, the original
instruction is lost. This ensures that the original instruction is
restored when a software break is removed.
The file was imported from this repository:
https://github.com/freebsd/freebsd.git
This commit was used:
commit 3ec0dc367bff27c345ad83240625b2057af391b9
Author: Sebastian Huber <sebastian.huber@embedded-brains.de>
Date: Mon Feb 7 14:16:16 2022 -0700
kern_ntptime.c: Remove ntp_init()
The ntp_init() function did set a couple of global objects to zero. These
objects are in the .bss section and already initialized to zero during kernel
or module loading.
Update #2348.
There are two places where we convert from a timecounter delta to
a bintime delta: tc_windup and bintime_off.
Both functions use the same calculations when the timecounter delta is
small. But for a large delta (greater than approximately an equivalent
of 1 second) the calculations were different. Both functions use
approximate calculations based on th_scale that avoid division. Both
produce values slightly greater than a true value, calculated with
division by tc_frequency, would be. tc_windup is slightly more
accurate, so its result is closer to the true value and, thus, smaller
than bintime_off result.
As a consequence there can be a jump back in time when time hands are
switched after a long period of time (a large delta). Just before the
switch the time would be calculated with a large delta from
th_offset_count in bintime_off. tc_windup does the switch using its own
calculations of a new th_offset using the large delta. As explained
earlier, the new th_offset may end up being less than the previously
produced binuptime. So, for a period of time new binuptime values may
be "back in time" comparing to values just before the switch.
Such a jump must never happen. All the code assumes that the uptime is
monotonically nondecreasing and some code works incorrectly when that
assumption is broken. For example, we have observed sleepq_timeout()
ignoring a timeout when the sbinuptime value obtained by the callout
code was greater than the expiration value, but the sbinuptime obtained
in sleepq_timeout() was less than it. In that case the target thread
would never get woken up.
The unified calculations should ensure the monotonic property of the
uptime.
The problem is quite rare as normally tc_windup should be called HZ
times per second (typically 1000 or 100). But it may happen in VMs on
very busy hypervisors where a VM's virtual CPU may not get an execution
time slot for a second or more.
Reviewed by: kib
MFC after: 2 weeks
Sponsored by: Panzura LLC
Hyper-V wants to register its MSR-based timecounter during
SI_SUB_HYPERVISOR, before SI_SUB_LOCK, since an emulated 8254 may not be
available for DELAY(). So we cannot use MTX_SYSINIT to initialize the
timecounter lock.
PR: 259878
Reviewed by: kib
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33014
Do not initialize Thread_Control::libc_reent if
CONFIGURE_DISABLE_NEWLIB_REENTRANCY is defined. This helps to catch errors
with a NULL pointer exception rather than a corruption of the thread control
block.
