Unlike some other architectures, RISC-V does not expose the current
privilege mode in any architecturally-defined register. That is intentional
to make it easier to implement virtualization in software, but a Unicorn
caller operates outside of the emulated hart and so it can and should be
able to observe and change the current privilege mode in order to properly
emulate certain behaviors of a real CPU.
The current privilege level is therefore now exposed as a new
pseudo-register using the name "priv", which matches the name of the
virtual register used by RISC-V's debug extension to allow the debugger
to read and change the privilege mode while the hart is halted. Unicorn's
use of it is conceptually similar to a debugger.
The bit encoding of this register is the same as specified in RISC-V Debug
Specification v1.0-rc3 Section 4.10.1. It's defined as a "virtual"
register exposing a subset of fields from the dcsr register, although here
it's implemented directly inside the Unicorn code because QEMU doesn't
currently have explicit support for the CSRs from the debug specification.
If it supports "dcsr" in a future release then this implementation could
change to wrap reading and writing that CSR and then projecting the "prv"
and "v" bitfields into the correct locations for the virtual register.
Some structs, specically CPUARMState is 16-bytes aligned.
This causes segment fault because gcc tends to vectorize
the assignment of the struct with infamous movaps tricks.
Without this patch, we fail on manylinux with 2.17 glibc
in release mode in i686.
qemu_memalign will ensure the alignment across platforms.
The wfi exception trigger behavior should take into account user mode,
hstatus.vtw, and the fact the an wfi might raise different types of
exceptions depending on various factors:
If supervisor mode is not present:
- an illegal instruction exception should be generated if user mode
executes and wfi instruction and mstatus.tw = 1.
If supervisor mode is present:
- when a wfi instruction is executed, an illegal exception should be triggered
if either the current mode is user or the mode is supervisor and mstatus.tw is
set.
Plus, if the hypervisor extensions are enabled:
- a virtual instruction exception should be raised when a wfi is executed from
virtual-user or virtual-supervisor and hstatus.vtw is set.
Signed-off-by: Jose Martins <josemartins90@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210420213656.85148-1-josemartins90@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This line appears to be trying to undo the effect of adding 4 to pc above,
but does so incorrectly and so ends up returning with next_pc earlier than
it was prior to decoding.
This causes the translator to malfunction because it does not expect
pc_next to decrease during decoding: this is effectively reporting that
the invalid construction has a negative size, which is impossible. The
decoder uses the increase in next_pc to decide the translation block size,
but converts it to uint16_t thereby causing a block containing _only_ an
invalid instruction to be treated as having size 65532 (reinterpreted -4)
and therefore the translation loop tries to find the next translation block
at 65532 bytes after the invalid instruction, which can cause a spurious
instruction access/page fault if the page containing that address is not
mapped as executable.
In practice we don't need to readjust the pc at all here because it is
correct to report that the invalid instruction is four bytes long. This
allows the translation loop to correctly find the next instruction, and
to avoid producing spurious TLB fills that might cause incorrect exceptions.
These APIs take size parameters, which can be used to properly bounds-check the
inputs and outputs for various registers. Additionally, all backends now throw
UC_ERR_ARG if the input register numbers are invalid.
Completes #1831.
Unicorn has included some ugly hacks to provide a envirement where vaddr == paddr.
These hacks where to use the full 64 bit mappings on x86 without init the mmu
and some memory redirect for MIPS.
The UC_TLB_CPU mode defaults to vaddr == paddr, therfor these hacks aren't
required anymore.
quit_request is for internal use. This means the IP register was updated and
qemu needs to rebuild the translation blocks.
stop_request is set by the user (uc_emu_stop) to indecate that unicorn sould
stop emulating.
