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Emulation
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=========
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QEMU's Tiny Code Generator (TCG) provides the ability to emulate a
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number of CPU architectures on any supported host platform. Both
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:ref:`System Emulation` and :ref:`User Mode Emulation` are supported
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depending on the guest architecture.
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.. list-table:: Supported Guest Architectures for Emulation
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:widths: 30 10 10 50
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:header-rows: 1
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* - Architecture (qemu name)
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- System
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- User
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- Notes
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* - Alpha
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- Yes
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- Yes
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- Legacy 64 bit RISC ISA developed by DEC
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* - Arm (arm, aarch64)
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- :ref:`Yes<ARM-System-emulator>`
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- Yes
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- Wide range of features, see :ref:`Arm Emulation` for details
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* - AVR
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- :ref:`Yes<AVR-System-emulator>`
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- No
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- 8 bit micro controller, often used in maker projects
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* - Hexagon
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- No
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- Yes
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- Family of DSPs by Qualcomm
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* - PA-RISC (hppa)
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- Yes
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- Yes
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- A legacy RISC system used in HP's old minicomputers
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* - x86 (i386, x86_64)
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- :ref:`Yes<QEMU-PC-System-emulator>`
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- Yes
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- The ubiquitous desktop PC CPU architecture, 32 and 64 bit.
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* - LoongArch
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- Yes
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- Yes
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- A MIPS-like 64bit RISC architecture developed in China
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* - m68k
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- :ref:`Yes<ColdFire-System-emulator>`
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- Yes
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- Motorola 68000 variants and ColdFire
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* - Microblaze
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- Yes
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- Yes
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- RISC based soft-core by Xilinx
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* - MIPS (mips*)
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- :ref:`Yes<MIPS-System-emulator>`
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- Yes
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- Venerable RISC architecture originally out of Stanford University
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* - OpenRISC
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- :ref:`Yes<OpenRISC-System-emulator>`
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- Yes
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- Open source RISC architecture developed by the OpenRISC community
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* - Power (ppc, ppc64)
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- :ref:`Yes<PowerPC-System-emulator>`
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- Yes
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- A general purpose RISC architecture now managed by IBM
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* - RISC-V
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- :ref:`Yes<RISC-V-System-emulator>`
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- Yes
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- An open standard RISC ISA maintained by RISC-V International
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* - RX
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- :ref:`Yes<RX-System-emulator>`
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- No
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- A 32 bit micro controller developed by Renesas
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* - s390x
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- :ref:`Yes<s390x-System-emulator>`
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- Yes
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- A 64 bit CPU found in IBM's System Z mainframes
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* - sh4
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- Yes
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- Yes
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- A 32 bit RISC embedded CPU developed by Hitachi
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* - SPARC (sparc, sparc64)
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- :ref:`Yes<Sparc32-System-emulator>`
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- Yes
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- A RISC ISA originally developed by Sun Microsystems
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* - Tricore
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- Yes
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- No
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- A 32 bit RISC/uController/DSP developed by Infineon
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* - Xtensa
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- :ref:`Yes<Xtensa-System-emulator>`
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- Yes
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- A configurable 32 bit soft core now owned by Cadence
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.. _Semihosting:
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Semihosting
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-----------
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Semihosting is a feature defined by the owner of the architecture to
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allow programs to interact with a debugging host system. On real
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hardware this is usually provided by an In-circuit emulator (ICE)
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hooked directly to the board. QEMU's implementation allows for
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semihosting calls to be passed to the host system or via the
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``gdbstub``.
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Generally semihosting makes it easier to bring up low level code before a
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more fully functional operating system has been enabled. On QEMU it
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also allows for embedded micro-controller code which typically doesn't
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have a full libc to be run as "bare-metal" code under QEMU's user-mode
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emulation. It is also useful for writing test cases and indeed a
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number of compiler suites as well as QEMU itself use semihosting calls
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to exit test code while reporting the success state.
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Semihosting is only available using TCG emulation. This is because the
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instructions to trigger a semihosting call are typically reserved
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causing most hypervisors to trap and fault on them.
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.. warning::
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Semihosting inherently bypasses any isolation there may be between
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the guest and the host. As a result a program using semihosting can
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happily trash your host system. Some semihosting calls (e.g.
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``SYS_READC``) can block execution indefinitely. You should only
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ever run trusted code with semihosting enabled.
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Redirection
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~~~~~~~~~~~
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Semihosting calls can be re-directed to a (potentially remote) gdb
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during debugging via the :ref:`gdbstub<GDB usage>`. Output to the
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semihosting console is configured as a ``chardev`` so can be
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redirected to a file, pipe or socket like any other ``chardev``
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device.
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Supported Targets
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~~~~~~~~~~~~~~~~~
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Most targets offer similar semihosting implementations with some
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minor changes to define the appropriate instruction to encode the
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semihosting call and which registers hold the parameters. They tend to
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presents a simple POSIX-like API which allows your program to read and
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write files, access the console and some other basic interactions.
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For full details of the ABI for a particular target, and the set of
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calls it provides, you should consult the semihosting specification
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for that architecture.
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.. note::
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QEMU makes an implementation decision to implement all file
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access in ``O_BINARY`` mode. The user-visible effect of this is
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regardless of the text/binary mode the program sets QEMU will
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always select a binary mode ensuring no line-terminator conversion
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is performed on input or output. This is because gdb semihosting
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support doesn't make the distinction between the modes and
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magically processing line endings can be confusing.
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.. list-table:: Guest Architectures supporting Semihosting
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:widths: 10 10 80
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:header-rows: 1
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* - Architecture
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- Modes
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- Specification
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* - Arm
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- System and User-mode
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- https://github.com/ARM-software/abi-aa/blob/main/semihosting/semihosting.rst
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* - m68k
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- System
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- https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=libgloss/m68k/m68k-semi.txt;hb=HEAD
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* - MIPS
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- System
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- Unified Hosting Interface (MD01069)
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* - RISC-V
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- System and User-mode
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- https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc
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* - Xtensa
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- System
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- Tensilica ISS SIMCALL
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TCG Plugins
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-----------
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QEMU TCG plugins provide a way for users to run experiments taking
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advantage of the total system control emulation can have over a guest.
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It provides a mechanism for plugins to subscribe to events during
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translation and execution and optionally callback into the plugin
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during these events. TCG plugins are unable to change the system state
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only monitor it passively. However they can do this down to an
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individual instruction granularity including potentially subscribing
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to all load and store operations.
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See the developer section of the manual for details about
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:ref:`writing plugins<TCG Plugins>`.
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Usage
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~~~~~
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Any QEMU binary with TCG support has plugins enabled by default.
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Earlier releases needed to be explicitly enabled with::
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configure --enable-plugins
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Once built a program can be run with multiple plugins loaded each with
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their own arguments::
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$QEMU $OTHER_QEMU_ARGS \
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-plugin contrib/plugins/libhowvec.so,inline=on,count=hint \
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-plugin contrib/plugins/libhotblocks.so
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Arguments are plugin specific and can be used to modify their
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behaviour. In this case the howvec plugin is being asked to use inline
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ops to count and break down the hint instructions by type.
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Linux user-mode emulation also evaluates the environment variable
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``QEMU_PLUGIN``::
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QEMU_PLUGIN="file=contrib/plugins/libhowvec.so,inline=on,count=hint" $QEMU
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QEMU plugins avoid to write directly to stdin/stderr, and use the log provided
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by the API (see function ``qemu_plugin_outs``).
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To show output, you may use this additional parameter::
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$QEMU $OTHER_QEMU_ARGS \
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-d plugin \
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-plugin contrib/plugins/libhowvec.so,inline=on,count=hint
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Example Plugins
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~~~~~~~~~~~~~~~
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There are a number of plugins included with QEMU and you are
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encouraged to contribute your own plugins plugins upstream. There is a
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``contrib/plugins`` directory where they can go. There are also some
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basic plugins that are used to test and exercise the API during the
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``make check-tcg`` target in ``tests/tcg/plugins`` that are never the
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less useful for basic analysis.
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Empty
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.....
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``tests/tcg/plugins/empty.c``
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Purely a test plugin for measuring the overhead of the plugins system
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itself. Does no instrumentation.
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Basic Blocks
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............
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``tests/tcg/plugins/bb.c``
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A very basic plugin which will measure execution in coarse terms as
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each basic block is executed. By default the results are shown once
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execution finishes::
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$ qemu-aarch64 -plugin tests/plugin/libbb.so \
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-d plugin ./tests/tcg/aarch64-linux-user/sha1
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SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
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bb's: 2277338, insns: 158483046
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Behaviour can be tweaked with the following arguments:
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.. list-table:: Basic Block plugin arguments
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:widths: 20 80
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:header-rows: 1
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* - Option
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- Description
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* - inline=true|false
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- Use faster inline addition of a single counter.
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* - idle=true|false
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- Dump the current execution stats whenever the guest vCPU idles
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Basic Block Vectors
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...................
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``contrib/plugins/bbv.c``
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The bbv plugin allows you to generate basic block vectors for use with the
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`SimPoint <https://cseweb.ucsd.edu/~calder/simpoint/>`__ analysis tool.
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.. list-table:: Basic block vectors arguments
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:widths: 20 80
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:header-rows: 1
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* - Option
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- Description
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* - interval=N
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- The interval to generate a basic block vector specified by the number of
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instructions (Default: N = 100000000)
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* - outfile=PATH
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- The path to output files.
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It will be suffixed with ``.N.bb`` where ``N`` is a vCPU index.
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Example::
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$ qemu-aarch64 \
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-plugin contrib/plugins/libbbv.so,interval=100,outfile=sha1 \
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tests/tcg/aarch64-linux-user/sha1
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SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
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$ du sha1.0.bb
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23128 sha1.0.bb
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Instruction
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...........
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``tests/tcg/plugins/insn.c``
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This is a basic instruction level instrumentation which can count the
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number of instructions executed on each core/thread::
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$ qemu-aarch64 -plugin tests/plugin/libinsn.so \
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-d plugin ./tests/tcg/aarch64-linux-user/threadcount
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Created 10 threads
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Done
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cpu 0 insns: 46765
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cpu 1 insns: 3694
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cpu 2 insns: 3694
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cpu 3 insns: 2994
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cpu 4 insns: 1497
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cpu 5 insns: 1497
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cpu 6 insns: 1497
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cpu 7 insns: 1497
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total insns: 63135
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Behaviour can be tweaked with the following arguments:
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.. list-table:: Instruction plugin arguments
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:widths: 20 80
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:header-rows: 1
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* - Option
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- Description
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* - inline=true|false
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- Use faster inline addition of a single counter.
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* - sizes=true|false
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- Give a summary of the instruction sizes for the execution
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* - match=<string>
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- Only instrument instructions matching the string prefix
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The ``match`` option will show some basic stats including how many
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instructions have executed since the last execution. For
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example::
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$ qemu-aarch64 -plugin tests/plugin/libinsn.so,match=bl \
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-d plugin ./tests/tcg/aarch64-linux-user/sha512-vector
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...
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0x40069c, 'bl #0x4002b0', 10 hits, 1093 match hits, Δ+1257 since last match, 98 avg insns/match
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0x4006ac, 'bl #0x403690', 10 hits, 1094 match hits, Δ+47 since last match, 98 avg insns/match
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0x4037fc, 'bl #0x4002b0', 18 hits, 1095 match hits, Δ+22 since last match, 98 avg insns/match
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0x400720, 'bl #0x403690', 10 hits, 1096 match hits, Δ+58 since last match, 98 avg insns/match
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0x4037fc, 'bl #0x4002b0', 19 hits, 1097 match hits, Δ+22 since last match, 98 avg insns/match
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0x400730, 'bl #0x403690', 10 hits, 1098 match hits, Δ+33 since last match, 98 avg insns/match
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0x4037ac, 'bl #0x4002b0', 12 hits, 1099 match hits, Δ+20 since last match, 98 avg insns/match
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...
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For more detailed execution tracing see the ``execlog`` plugin for
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other options.
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Memory
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......
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``tests/tcg/plugins/mem.c``
|
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Basic instruction level memory instrumentation::
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$ qemu-aarch64 -plugin tests/plugin/libmem.so,inline=true \
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-d plugin ./tests/tcg/aarch64-linux-user/sha1
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SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
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inline mem accesses: 79525013
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Behaviour can be tweaked with the following arguments:
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|
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.. list-table:: Memory plugin arguments
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:widths: 20 80
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:header-rows: 1
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|
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* - Option
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- Description
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* - inline=true|false
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- Use faster inline addition of a single counter
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* - callback=true|false
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- Use callbacks on each memory instrumentation.
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* - hwaddr=true|false
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- Count IO accesses (only for system emulation)
|
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System Calls
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............
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|
``tests/tcg/plugins/syscall.c``
|
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A basic syscall tracing plugin. This only works for user-mode. By
|
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default it will give a summary of syscall stats at the end of the
|
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run::
|
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$ qemu-aarch64 -plugin tests/plugin/libsyscall \
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-d plugin ./tests/tcg/aarch64-linux-user/threadcount
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Created 10 threads
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Done
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syscall no. calls errors
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226 12 0
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99 11 11
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115 11 0
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222 11 0
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93 10 0
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220 10 0
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233 10 0
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215 8 0
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214 4 0
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134 2 0
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64 2 0
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96 1 0
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94 1 0
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80 1 0
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261 1 0
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78 1 0
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160 1 0
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135 1 0
|
|
|
|
Behaviour can be tweaked with the following arguments:
|
|
|
|
.. list-table:: Syscall plugin arguments
|
|
:widths: 20 80
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:header-rows: 1
|
|
|
|
* - Option
|
|
- Description
|
|
* - print=true|false
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- Print the number of times each syscall is called
|
|
* - log_writes=true|false
|
|
- Log the buffer of each write syscall in hexdump format
|
|
|
|
Test inline operations
|
|
......................
|
|
|
|
``tests/plugins/inline.c``
|
|
|
|
This plugin is used for testing all inline operations, conditional callbacks and
|
|
scoreboard. It prints a per-cpu summary of all events.
|
|
|
|
|
|
Hot Blocks
|
|
..........
|
|
|
|
``contrib/plugins/hotblocks.c``
|
|
|
|
The hotblocks plugin allows you to examine the where hot paths of
|
|
execution are in your program. Once the program has finished you will
|
|
get a sorted list of blocks reporting the starting PC, translation
|
|
count, number of instructions and execution count. This will work best
|
|
with linux-user execution as system emulation tends to generate
|
|
re-translations as blocks from different programs get swapped in and
|
|
out of system memory.
|
|
|
|
Example::
|
|
|
|
$ qemu-aarch64 \
|
|
-plugin contrib/plugins/libhotblocks.so -d plugin \
|
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./tests/tcg/aarch64-linux-user/sha1
|
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SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
|
|
collected 903 entries in the hash table
|
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pc, tcount, icount, ecount
|
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0x0000000041ed10, 1, 5, 66087
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0x000000004002b0, 1, 4, 66087
|
|
...
|
|
|
|
|
|
Hot Pages
|
|
.........
|
|
|
|
``contrib/plugins/hotpages.c``
|
|
|
|
Similar to hotblocks but this time tracks memory accesses::
|
|
|
|
$ qemu-aarch64 \
|
|
-plugin contrib/plugins/libhotpages.so -d plugin \
|
|
./tests/tcg/aarch64-linux-user/sha1
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|
SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
|
|
Addr, RCPUs, Reads, WCPUs, Writes
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0x000055007fe000, 0x0001, 31747952, 0x0001, 8835161
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0x000055007ff000, 0x0001, 29001054, 0x0001, 8780625
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0x00005500800000, 0x0001, 687465, 0x0001, 335857
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0x0000000048b000, 0x0001, 130594, 0x0001, 355
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0x0000000048a000, 0x0001, 1826, 0x0001, 11
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|
|
|
The hotpages plugin can be configured using the following arguments:
|
|
|
|
.. list-table:: Hot pages arguments
|
|
:widths: 20 80
|
|
:header-rows: 1
|
|
|
|
* - Option
|
|
- Description
|
|
* - sortby=reads|writes|address
|
|
- Log the data sorted by either the number of reads, the number of writes, or
|
|
memory address. (Default: entries are sorted by the sum of reads and writes)
|
|
* - io=on
|
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- Track IO addresses. Only relevant to full system emulation. (Default: off)
|
|
* - pagesize=N
|
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- The page size used. (Default: N = 4096)
|
|
|
|
Instruction Distribution
|
|
........................
|
|
|
|
``contrib/plugins/howvec.c``
|
|
|
|
This is an instruction classifier so can be used to count different
|
|
types of instructions. It has a number of options to refine which get
|
|
counted. You can give a value to the ``count`` argument for a class of
|
|
instructions to break it down fully, so for example to see all the system
|
|
registers accesses::
|
|
|
|
$ qemu-system-aarch64 $(QEMU_ARGS) \
|
|
-append "root=/dev/sda2 systemd.unit=benchmark.service" \
|
|
-smp 4 -plugin ./contrib/plugins/libhowvec.so,count=sreg -d plugin
|
|
|
|
which will lead to a sorted list after the class breakdown::
|
|
|
|
Instruction Classes:
|
|
Class: UDEF not counted
|
|
Class: SVE (68 hits)
|
|
Class: PCrel addr (47789483 hits)
|
|
Class: Add/Sub (imm) (192817388 hits)
|
|
Class: Logical (imm) (93852565 hits)
|
|
Class: Move Wide (imm) (76398116 hits)
|
|
Class: Bitfield (44706084 hits)
|
|
Class: Extract (5499257 hits)
|
|
Class: Cond Branch (imm) (147202932 hits)
|
|
Class: Exception Gen (193581 hits)
|
|
Class: NOP not counted
|
|
Class: Hints (6652291 hits)
|
|
Class: Barriers (8001661 hits)
|
|
Class: PSTATE (1801695 hits)
|
|
Class: System Insn (6385349 hits)
|
|
Class: System Reg counted individually
|
|
Class: Branch (reg) (69497127 hits)
|
|
Class: Branch (imm) (84393665 hits)
|
|
Class: Cmp & Branch (110929659 hits)
|
|
Class: Tst & Branch (44681442 hits)
|
|
Class: AdvSimd ldstmult (736 hits)
|
|
Class: ldst excl (9098783 hits)
|
|
Class: Load Reg (lit) (87189424 hits)
|
|
Class: ldst noalloc pair (3264433 hits)
|
|
Class: ldst pair (412526434 hits)
|
|
Class: ldst reg (imm) (314734576 hits)
|
|
Class: Loads & Stores (2117774 hits)
|
|
Class: Data Proc Reg (223519077 hits)
|
|
Class: Scalar FP (31657954 hits)
|
|
Individual Instructions:
|
|
Instr: mrs x0, sp_el0 (2682661 hits) (op=0xd5384100/ System Reg)
|
|
Instr: mrs x1, tpidr_el2 (1789339 hits) (op=0xd53cd041/ System Reg)
|
|
Instr: mrs x2, tpidr_el2 (1513494 hits) (op=0xd53cd042/ System Reg)
|
|
Instr: mrs x0, tpidr_el2 (1490823 hits) (op=0xd53cd040/ System Reg)
|
|
Instr: mrs x1, sp_el0 (933793 hits) (op=0xd5384101/ System Reg)
|
|
Instr: mrs x2, sp_el0 (699516 hits) (op=0xd5384102/ System Reg)
|
|
Instr: mrs x4, tpidr_el2 (528437 hits) (op=0xd53cd044/ System Reg)
|
|
Instr: mrs x30, ttbr1_el1 (480776 hits) (op=0xd538203e/ System Reg)
|
|
Instr: msr ttbr1_el1, x30 (480713 hits) (op=0xd518203e/ System Reg)
|
|
Instr: msr vbar_el1, x30 (480671 hits) (op=0xd518c01e/ System Reg)
|
|
...
|
|
|
|
To find the argument shorthand for the class you need to examine the
|
|
source code of the plugin at the moment, specifically the ``*opt``
|
|
argument in the InsnClassExecCount tables.
|
|
|
|
Lockstep Execution
|
|
..................
|
|
|
|
``contrib/plugins/lockstep.c``
|
|
|
|
This is a debugging tool for developers who want to find out when and
|
|
where execution diverges after a subtle change to TCG code generation.
|
|
It is not an exact science and results are likely to be mixed once
|
|
asynchronous events are introduced. While the use of -icount can
|
|
introduce determinism to the execution flow it doesn't always follow
|
|
the translation sequence will be exactly the same. Typically this is
|
|
caused by a timer firing to service the GUI causing a block to end
|
|
early. However in some cases it has proved to be useful in pointing
|
|
people at roughly where execution diverges. The only argument you need
|
|
for the plugin is a path for the socket the two instances will
|
|
communicate over::
|
|
|
|
|
|
$ qemu-system-sparc -monitor none -parallel none \
|
|
-net none -M SS-20 -m 256 -kernel day11/zImage.elf \
|
|
-plugin ./contrib/plugins/liblockstep.so,sockpath=lockstep-sparc.sock \
|
|
-d plugin,nochain
|
|
|
|
which will eventually report::
|
|
|
|
qemu-system-sparc: warning: nic lance.0 has no peer
|
|
@ 0x000000ffd06678 vs 0x000000ffd001e0 (2/1 since last)
|
|
@ 0x000000ffd07d9c vs 0x000000ffd06678 (3/1 since last)
|
|
Δ insn_count @ 0x000000ffd07d9c (809900609) vs 0x000000ffd06678 (809900612)
|
|
previously @ 0x000000ffd06678/10 (809900609 insns)
|
|
previously @ 0x000000ffd001e0/4 (809900599 insns)
|
|
previously @ 0x000000ffd080ac/2 (809900595 insns)
|
|
previously @ 0x000000ffd08098/5 (809900593 insns)
|
|
previously @ 0x000000ffd080c0/1 (809900588 insns)
|
|
|
|
|
|
Hardware Profile
|
|
................
|
|
|
|
``contrib/plugins/hwprofile.c``
|
|
|
|
The hwprofile tool can only be used with system emulation and allows
|
|
the user to see what hardware is accessed how often. It has a number of options:
|
|
|
|
.. list-table:: Hardware Profile arguments
|
|
:widths: 20 80
|
|
:header-rows: 1
|
|
|
|
* - Option
|
|
- Description
|
|
* - track=[read|write]
|
|
- By default the plugin tracks both reads and writes. You can use
|
|
this option to limit the tracking to just one class of accesses.
|
|
* - source
|
|
- Will include a detailed break down of what the guest PC that made the
|
|
access was. Not compatible with the pattern option. Example output::
|
|
|
|
cirrus-low-memory @ 0xfffffd00000a0000
|
|
pc:fffffc0000005cdc, 1, 256
|
|
pc:fffffc0000005ce8, 1, 256
|
|
pc:fffffc0000005cec, 1, 256
|
|
|
|
* - pattern
|
|
- Instead break down the accesses based on the offset into the HW
|
|
region. This can be useful for seeing the most used registers of
|
|
a device. Example output::
|
|
|
|
pci0-conf @ 0xfffffd01fe000000
|
|
off:00000004, 1, 1
|
|
off:00000010, 1, 3
|
|
off:00000014, 1, 3
|
|
off:00000018, 1, 2
|
|
off:0000001c, 1, 2
|
|
off:00000020, 1, 2
|
|
...
|
|
|
|
|
|
Execution Log
|
|
.............
|
|
|
|
``contrib/plugins/execlog.c``
|
|
|
|
The execlog tool traces executed instructions with memory access. It can be used
|
|
for debugging and security analysis purposes.
|
|
Please be aware that this will generate a lot of output.
|
|
|
|
The plugin needs default argument::
|
|
|
|
$ qemu-system-arm $(QEMU_ARGS) \
|
|
-plugin ./contrib/plugins/libexeclog.so -d plugin
|
|
|
|
which will output an execution trace following this structure::
|
|
|
|
# vCPU, vAddr, opcode, disassembly[, load/store, memory addr, device]...
|
|
0, 0xa12, 0xf8012400, "movs r4, #0"
|
|
0, 0xa14, 0xf87f42b4, "cmp r4, r6"
|
|
0, 0xa16, 0xd206, "bhs #0xa26"
|
|
0, 0xa18, 0xfff94803, "ldr r0, [pc, #0xc]", load, 0x00010a28, RAM
|
|
0, 0xa1a, 0xf989f000, "bl #0xd30"
|
|
0, 0xd30, 0xfff9b510, "push {r4, lr}", store, 0x20003ee0, RAM, store, 0x20003ee4, RAM
|
|
0, 0xd32, 0xf9893014, "adds r0, #0x14"
|
|
0, 0xd34, 0xf9c8f000, "bl #0x10c8"
|
|
0, 0x10c8, 0xfff96c43, "ldr r3, [r0, #0x44]", load, 0x200000e4, RAM
|
|
|
|
Please note that you need to configure QEMU with Capstone support to get disassembly.
|
|
|
|
The output can be filtered to only track certain instructions or
|
|
addresses using the ``ifilter`` or ``afilter`` options. You can stack the
|
|
arguments if required::
|
|
|
|
$ qemu-system-arm $(QEMU_ARGS) \
|
|
-plugin ./contrib/plugins/libexeclog.so,ifilter=st1w,afilter=0x40001808 -d plugin
|
|
|
|
This plugin can also dump registers when they change value. Specify the name of the
|
|
registers with multiple ``reg`` options. You can also use glob style matching if you wish::
|
|
|
|
$ qemu-system-arm $(QEMU_ARGS) \
|
|
-plugin ./contrib/plugins/libexeclog.so,reg=\*_el2,reg=sp -d plugin
|
|
|
|
Be aware that each additional register to check will slow down
|
|
execution quite considerably. You can optimise the number of register
|
|
checks done by using the rdisas option. This will only instrument
|
|
instructions that mention the registers in question in disassembly.
|
|
This is not foolproof as some instructions implicitly change
|
|
instructions. You can use the ifilter to catch these cases::
|
|
|
|
$ qemu-system-arm $(QEMU_ARGS) \
|
|
-plugin ./contrib/plugins/libexeclog.so,ifilter=msr,ifilter=blr,reg=x30,reg=\*_el1,rdisas=on
|
|
|
|
Cache Modelling
|
|
...............
|
|
|
|
``contrib/plugins/cache.c``
|
|
|
|
Cache modelling plugin that measures the performance of a given L1 cache
|
|
configuration, and optionally a unified L2 per-core cache when a given working
|
|
set is run::
|
|
|
|
$ qemu-x86_64 -plugin ./contrib/plugins/libcache.so \
|
|
-d plugin -D cache.log ./tests/tcg/x86_64-linux-user/float_convs
|
|
|
|
will report the following::
|
|
|
|
core #, data accesses, data misses, dmiss rate, insn accesses, insn misses, imiss rate
|
|
0 996695 508 0.0510% 2642799 18617 0.7044%
|
|
|
|
address, data misses, instruction
|
|
0x424f1e (_int_malloc), 109, movq %rax, 8(%rcx)
|
|
0x41f395 (_IO_default_xsputn), 49, movb %dl, (%rdi, %rax)
|
|
0x42584d (ptmalloc_init.part.0), 33, movaps %xmm0, (%rax)
|
|
0x454d48 (__tunables_init), 20, cmpb $0, (%r8)
|
|
...
|
|
|
|
address, fetch misses, instruction
|
|
0x4160a0 (__vfprintf_internal), 744, movl $1, %ebx
|
|
0x41f0a0 (_IO_setb), 744, endbr64
|
|
0x415882 (__vfprintf_internal), 744, movq %r12, %rdi
|
|
0x4268a0 (__malloc), 696, andq $0xfffffffffffffff0, %rax
|
|
...
|
|
|
|
The plugin has a number of arguments, all of them are optional:
|
|
|
|
.. list-table:: Cache modelling arguments
|
|
:widths: 20 80
|
|
:header-rows: 1
|
|
|
|
* - Option
|
|
- Description
|
|
* - limit=N
|
|
- Print top N icache and dcache thrashing instructions along with
|
|
their address, number of misses, and its disassembly. (default: 32)
|
|
* - icachesize=N
|
|
iblksize=B
|
|
iassoc=A
|
|
- Instruction cache configuration arguments. They specify the
|
|
cache size, block size, and associativity of the instruction
|
|
cache, respectively. (default: N = 16384, B = 64, A = 8)
|
|
* - dcachesize=N
|
|
- Data cache size (default: 16834)
|
|
* - dblksize=B
|
|
- Data cache block size (default: 64)
|
|
* - dassoc=A
|
|
- Data cache associativity (default: 8)
|
|
* - evict=POLICY
|
|
- Sets the eviction policy to POLICY. Available policies are:
|
|
``lru``, ``fifo``, and ``rand``. The plugin will use
|
|
the specified policy for both instruction and data caches.
|
|
(default: POLICY = ``lru``)
|
|
* - cores=N
|
|
- Sets the number of cores for which we maintain separate icache
|
|
and dcache. (default: for linux-user, N = 1, for full system
|
|
emulation: N = cores available to guest)
|
|
* - l2=on
|
|
- Simulates a unified L2 cache (stores blocks for both
|
|
instructions and data) using the default L2 configuration (cache
|
|
size = 2MB, associativity = 16-way, block size = 64B).
|
|
* - l2cachesize=N
|
|
- L2 cache size (default: 2097152 (2MB)), implies ``l2=on``
|
|
* - l2blksize=B
|
|
- L2 cache block size (default: 64), implies ``l2=on``
|
|
* - l2assoc=A
|
|
- L2 cache associativity (default: 16), implies ``l2=on``
|
|
|
|
Stop on Trigger
|
|
...............
|
|
|
|
``contrib/plugins/stoptrigger.c``
|
|
|
|
The stoptrigger plugin allows to setup triggers to stop emulation.
|
|
It can be used for research purposes to launch some code and precisely stop it
|
|
and understand where its execution flow went.
|
|
|
|
Two types of triggers can be configured: a count of instructions to stop at,
|
|
or an address to stop at. Multiple triggers can be set at once.
|
|
|
|
By default, QEMU will exit with return code 0. A custom return code can be
|
|
configured for each trigger using ``:CODE`` syntax.
|
|
|
|
For example, to stop at the 20-th instruction with return code 41, at address
|
|
0xd4 with return code 0 or at address 0xd8 with return code 42::
|
|
|
|
$ qemu-system-aarch64 $(QEMU_ARGS) \
|
|
-plugin ./contrib/plugins/libstoptrigger.so,icount=20:41,addr=0xd4,addr=0xd8:42 -d plugin
|
|
|
|
The plugin will log the reason of exit, for example::
|
|
|
|
0xd4 reached, exiting
|
|
|
|
Limit instructions per second
|
|
.............................
|
|
|
|
This plugin can limit the number of Instructions Per Second that are executed::
|
|
|
|
# get number of instructions
|
|
$ num_insn=$(./build/qemu-x86_64 -plugin ./build/tests/plugin/libinsn.so -d plugin /bin/true |& grep total | sed -e 's/.*: //')
|
|
# limit speed to execute in 10 seconds
|
|
$ time ./build/qemu-x86_64 -plugin ./build/contrib/plugins/libips.so,ips=$(($num_insn/10)) /bin/true
|
|
real 10.000s
|
|
|
|
|
|
.. list-table:: IPS arguments
|
|
:widths: 20 80
|
|
:header-rows: 1
|
|
|
|
* - Option
|
|
- Description
|
|
* - ips=N
|
|
- Maximum number of instructions per cpu that can be executed in one second.
|
|
The plugin will sleep when the given number of instructions is reached.
|
|
|
|
Other emulation features
|
|
------------------------
|
|
|
|
When running system emulation you can also enable deterministic
|
|
execution which allows for repeatable record/replay debugging. See
|
|
:ref:`Record/Replay<replay>` for more details.
|