QEMU TCG Plugins

QEMU TCG plugins provide a way for users to run experiments taking advantage of the total system control emulation can have over a guest. It provides a mechanism for plugins to subscribe to events during translation and execution and optionally callback into the plugin during these events. TCG plugins are unable to change the system state only monitor it passively. However they can do this down to an individual instruction granularity including potentially subscribing to all load and store operations.

Usage

Any QEMU binary with TCG support has plugins enabled by default. Earlier releases needed to be explicitly enabled with:

configure --enable-plugins

Once built a program can be run with multiple plugins loaded each with their own arguments:

$QEMU $OTHER_QEMU_ARGS \
    -plugin contrib/plugin/libhowvec.so,inline=on,count=hint \
    -plugin contrib/plugin/libhotblocks.so

Arguments are plugin specific and can be used to modify their behaviour. In this case the howvec plugin is being asked to use inline ops to count and break down the hint instructions by type.

Linux user-mode emulation also evaluates the environment variable QEMU_PLUGIN:

QEMU_PLUGIN="file=contrib/plugins/libhowvec.so,inline=on,count=hint" $QEMU

Writing plugins

API versioning

This is a new feature for QEMU and it does allow people to develop out-of-tree plugins that can be dynamically linked into a running QEMU process. However the project reserves the right to change or break the API should it need to do so. The best way to avoid this is to submit your plugin upstream so they can be updated if/when the API changes.

All plugins need to declare a symbol which exports the plugin API version they were built against. This can be done simply by:

QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;

The core code will refuse to load a plugin that doesn’t export a qemu_plugin_version symbol or if plugin version is outside of QEMU’s supported range of API versions.

Additionally the qemu_info_t structure which is passed to the qemu_plugin_install method of a plugin will detail the minimum and current API versions supported by QEMU. The API version will be incremented if new APIs are added. The minimum API version will be incremented if existing APIs are changed or removed.

Lifetime of the query handle

Each callback provides an opaque anonymous information handle which can usually be further queried to find out information about a translation, instruction or operation. The handles themselves are only valid during the lifetime of the callback so it is important that any information that is needed is extracted during the callback and saved by the plugin.

Plugin life cycle

First the plugin is loaded and the public qemu_plugin_install function is called. The plugin will then register callbacks for various plugin events. Generally plugins will register a handler for the atexit if they want to dump a summary of collected information once the program/system has finished running.

When a registered event occurs the plugin callback is invoked. The callbacks may provide additional information. In the case of a translation event the plugin has an option to enumerate the instructions in a block of instructions and optionally register callbacks to some or all instructions when they are executed.

There is also a facility to add an inline event where code to increment a counter can be directly inlined with the translation. Currently only a simple increment is supported. This is not atomic so can miss counts. If you want absolute precision you should use a callback which can then ensure atomicity itself.

Finally when QEMU exits all the registered atexit callbacks are invoked.

Exposure of QEMU internals

The plugin architecture actively avoids leaking implementation details about how QEMU’s translation works to the plugins. While there are conceptions such as translation time and translation blocks the details are opaque to plugins. The plugin is able to query select details of instructions and system configuration only through the exported qemu_plugin functions.

However the following assumptions can be made:

Translation Blocks

All code will go through a translation phase although not all translations will be necessarily be executed. You need to instrument actual executions to track what is happening.

It is quite normal to see the same address translated multiple times. If you want to track the code in system emulation you should examine the underlying physical address (qemu_plugin_insn_haddr) to take into account the effects of virtual memory although if the system does paging this will change too.

Not all instructions in a block will always execute so if its important to track individual instruction execution you need to instrument them directly. However asynchronous interrupts will not change control flow mid-block.

Instructions

Instruction instrumentation runs before the instruction executes. You can be can be sure the instruction will be dispatched, but you can’t be sure it will complete. Generally this will be because of a synchronous exception (e.g. SIGILL) triggered by the instruction attempting to execute. If you want to be sure you will need to instrument the next instruction as well. See the execlog.c plugin for examples of how to track this and finalise details after execution.

Memory Accesses

Memory callbacks are called after a successful load or store. Unsuccessful operations (i.e. faults) will not be visible to memory instrumentation although the execution side effects can be observed (e.g. entering a exception handler).

System Idle and Resume States

The qemu_plugin_register_vcpu_idle_cb and qemu_plugin_register_vcpu_resume_cb functions can be used to track when CPUs go into and return from sleep states when waiting for external I/O. Be aware though that these may occur less frequently than in real HW due to the inefficiencies of emulation giving less chance for the CPU to idle.

Internals

Locking

We have to ensure we cannot deadlock, particularly under MTTCG. For this we acquire a lock when called from plugin code. We also keep the list of callbacks under RCU so that we do not have to hold the lock when calling the callbacks. This is also for performance, since some callbacks (e.g. memory access callbacks) might be called very frequently.

A consequence of this is that we keep our own list of CPUs, so that we do not have to worry about locking order wrt cpu_list_lock.

Use a recursive lock, since we can get registration calls from callbacks.

As a result registering/unregistering callbacks is “slow”, since it takes a lock. But this is very infrequent; we want performance when calling (or not calling) callbacks, not when registering them. Using RCU is great for this.

We support the uninstallation of a plugin at any time (e.g. from plugin callbacks). This allows plugins to remove themselves if they no longer want to instrument the code. This operation is asynchronous which means callbacks may still occur after the uninstall operation is requested. The plugin isn’t completely uninstalled until the safe work has executed while all vCPUs are quiescent.

Example Plugins

There are a number of plugins included with QEMU and you are encouraged to contribute your own plugins plugins upstream. There is a contrib/plugins directory where they can go. There are also some basic plugins that are used to test and exercise the API during the make check-tcg target in tests\plugins.

tests/plugins/empty.c

Purely a test plugin for measuring the overhead of the plugins system itself. Does no instrumentation.

tests/plugins/bb.c

A very basic plugin which will measure execution in course terms as each basic block is executed. By default the results are shown once execution finishes:

$ qemu-aarch64 -plugin tests/plugin/libbb.so \
    -d plugin ./tests/tcg/aarch64-linux-user/sha1
SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
bb's: 2277338, insns: 158483046

Behaviour can be tweaked with the following arguments:

inline=true|false

Use faster inline addition of a single counter. Not per-cpu and not thread safe.

idle=true|false

Dump the current execution stats whenever the guest vCPU idles

tests/plugins/insn.c

This is a basic instruction level instrumentation which can count the number of instructions executed on each core/thread:

$ qemu-aarch64 -plugin tests/plugin/libinsn.so \
    -d plugin ./tests/tcg/aarch64-linux-user/threadcount
Created 10 threads
Done
cpu 0 insns: 46765
cpu 1 insns: 3694
cpu 2 insns: 3694
cpu 3 insns: 2994
cpu 4 insns: 1497
cpu 5 insns: 1497
cpu 6 insns: 1497
cpu 7 insns: 1497
total insns: 63135

Behaviour can be tweaked with the following arguments:

inline=true|false

Use faster inline addition of a single counter. Not per-cpu and not thread safe.

sizes=true|false

Give a summary of the instruction sizes for the execution

match=<string>

Only instrument instructions matching the string prefix. Will show some basic stats including how many instructions have executed since the last execution. For example:
$ qemu-aarch64 -plugin tests/plugin/libinsn.so,match=bl \
    -d plugin ./tests/tcg/aarch64-linux-user/sha512-vector
...
0x40069c, 'bl #0x4002b0', 10 hits, 1093 match hits, Δ+1257 since last match, 98 avg insns/match
0x4006ac, 'bl #0x403690', 10 hits, 1094 match hits, Δ+47 since last match, 98 avg insns/match
0x4037fc, 'bl #0x4002b0', 18 hits, 1095 match hits, Δ+22 since last match, 98 avg insns/match
0x400720, 'bl #0x403690', 10 hits, 1096 match hits, Δ+58 since last match, 98 avg insns/match
0x4037fc, 'bl #0x4002b0', 19 hits, 1097 match hits, Δ+22 since last match, 98 avg insns/match
0x400730, 'bl #0x403690', 10 hits, 1098 match hits, Δ+33 since last match, 98 avg insns/match
0x4037ac, 'bl #0x4002b0', 12 hits, 1099 match hits, Δ+20 since last match, 98 avg insns/match
...

For more detailed execution tracing see the execlog plugin for other options.

tests/plugins/mem.c

Basic instruction level memory instrumentation:

$ qemu-aarch64 -plugin tests/plugin/libmem.so,inline=true \
    -d plugin ./tests/tcg/aarch64-linux-user/sha1
SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
inline mem accesses: 79525013

Behaviour can be tweaked with the following arguments:

inline=true|false

Use faster inline addition of a single counter. Not per-cpu and not thread safe.

callback=true|false

Use callbacks on each memory instrumentation.

hwaddr=true|false

Count IO accesses (only for system emulation)

tests/plugins/syscall.c

A basic syscall tracing plugin. This only works for user-mode. By default it will give a summary of syscall stats at the end of the run:

$ qemu-aarch64 -plugin tests/plugin/libsyscall \
    -d plugin ./tests/tcg/aarch64-linux-user/threadcount
Created 10 threads
Done
syscall no.  calls  errors
        12     0
         11     11
        11     0
        11     0
         10     0
        10     0
        10     0
        8      0
        4      0
        2      0
         2      0
         1      0
         1      0
         1      0
        1      0
         1      0
        1      0
        1      0

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.

If your program is single-threaded you can use the inline option for slightly faster (but not thread safe) counters.

Example:

$ qemu-aarch64 \
  -plugin contrib/plugins/libhotblocks.so -d plugin \
  ./tests/tcg/aarch64-linux-user/sha1
SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
collected 903 entries in the hash table
pc, tcount, icount, ecount
0x0000000041ed10, 1, 5, 66087
0x000000004002b0, 1, 4, 66087
...

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
SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
Addr, RCPUs, Reads, WCPUs, Writes
0x000055007fe000, 0x0001, 31747952, 0x0001, 8835161
0x000055007ff000, 0x0001, 29001054, 0x0001, 8780625
0x00005500800000, 0x0001, 687465, 0x0001, 335857
0x0000000048b000, 0x0001, 130594, 0x0001, 355
0x0000000048a000, 0x0001, 1826, 0x0001, 11

The hotpages plugin can be configured using the following arguments:

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

Track IO addresses. Only relevant to full system emulation. (Default: off)

pagesize=N

The page size used. (Default: N = 4096)

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.

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)

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:

track=read or track=write

By default the plugin tracks both reads and writes. You can use one of these options 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
  ...

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

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:

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

dblksize=B

dassoc=A

Data cache configuration arguments. They specify the cache size, block size, and associativity of the data cache, respectively. (default: N = 16384, B = 64, A = 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

l2blksize=B

l2assoc=A

L2 cache configuration arguments. They specify the cache size, block size, and associativity of the L2 cache, respectively. Setting any of the L2 configuration arguments implies l2=on. (default: N = 2097152 (2MB), B = 64, A = 16)

Plugin API

The following API is generated from the inline documentation in include/qemu/qemu-plugin.h. Please ensure any updates to the API include the full kernel-doc annotations.

type qemu_plugin_id_t: Unique plugin ID

struct qemu_info_t: system information for plugins

Definition

struct qemu_info_t {
  const char *target_name;
  struct {
    int min;
    int cur;
  } version;
  bool system_emulation;
  union {
    struct {
      int smp_vcpus;
      int max_vcpus;
    } system;
  };
};

Members

target_name: string describing architecture
version: minimum and current plugin API level
system_emulation: is this a full system emulation?
{unnamed_union}: anonymous
system: information relevant to system emulation

Description

This structure provides for some limited information about the system to allow the plugin to make decisions on how to proceed. For example it might only be suitable for running on some guest architectures or when under full system emulation.

int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info, int argc, char **argv): Install a plugin

Parameters

qemu_plugin_id_t id: this plugin’s opaque ID
const qemu_info_t *info: a block describing some details about the guest
int argc: number of arguments
char **argv: array of arguments (argc elements)

Description

All plugins must export this symbol which is called when the plugin is first loaded. Calling qemu_plugin_uninstall() from this function is a bug.

Note

info is only live during the call. Copy any information we want to keep. argv remains valid throughout the lifetime of the loaded plugin.

Return

0 on successful loading, !0 for an error.

qemu_plugin_simple_cb_t: Typedef: simple callback

Syntax

void qemu_plugin_simple_cb_t (qemu_plugin_id_t id)

Parameters

qemu_plugin_id_t id: the unique qemu_plugin_id_t

Description

This callback passes no information aside from the unique id.

qemu_plugin_udata_cb_t: Typedef: callback with user data

Syntax

void qemu_plugin_udata_cb_t (qemu_plugin_id_t id, void *userdata)

Parameters

qemu_plugin_id_t id: the unique qemu_plugin_id_t
void *userdata: a pointer to some user data supplied when the callback was registered.

qemu_plugin_vcpu_simple_cb_t: Typedef: vcpu callback

Syntax

void qemu_plugin_vcpu_simple_cb_t (qemu_plugin_id_t id, unsigned int vcpu_index)

Parameters

qemu_plugin_id_t id: the unique qemu_plugin_id_t
unsigned int vcpu_index: the current vcpu context

qemu_plugin_vcpu_udata_cb_t: Typedef: vcpu callback

Syntax

void qemu_plugin_vcpu_udata_cb_t (unsigned int vcpu_index, void *userdata)

Parameters

unsigned int vcpu_index: the current vcpu context
void *userdata: a pointer to some user data supplied when the callback was registered.

void qemu_plugin_uninstall(qemu_plugin_id_t id, qemu_plugin_simple_cb_t cb): Uninstall a plugin

Parameters

qemu_plugin_id_t id: this plugin’s opaque ID
qemu_plugin_simple_cb_t cb: callback to be called once the plugin has been removed

Description

Do NOT assume that the plugin has been uninstalled once this function returns. Plugins are uninstalled asynchronously, and therefore the given plugin receives callbacks until cb is called.

Note

Calling this function from qemu_plugin_install() is a bug.

void qemu_plugin_reset(qemu_plugin_id_t id, qemu_plugin_simple_cb_t cb): Reset a plugin

Parameters

qemu_plugin_id_t id: this plugin’s opaque ID
qemu_plugin_simple_cb_t cb: callback to be called once the plugin has been reset

Description

Unregisters all callbacks for the plugin given by id.

Do NOT assume that the plugin has been reset once this function returns. Plugins are reset asynchronously, and therefore the given plugin receives callbacks until cb is called.

void qemu_plugin_register_vcpu_init_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_simple_cb_t cb): register a vCPU initialization callback

Parameters

qemu_plugin_id_t id: plugin ID
qemu_plugin_vcpu_simple_cb_t cb: callback function

Description

The cb function is called every time a vCPU is initialized.

See also: qemu_plugin_register_vcpu_exit_cb()

void qemu_plugin_register_vcpu_exit_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_simple_cb_t cb): register a vCPU exit callback

Parameters

qemu_plugin_id_t id: plugin ID
qemu_plugin_vcpu_simple_cb_t cb: callback function

Description

The cb function is called every time a vCPU exits.

See also: qemu_plugin_register_vcpu_init_cb()

void qemu_plugin_register_vcpu_idle_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_simple_cb_t cb): register a vCPU idle callback

Parameters

qemu_plugin_id_t id: plugin ID
qemu_plugin_vcpu_simple_cb_t cb: callback function

Description

The cb function is called every time a vCPU idles.

void qemu_plugin_register_vcpu_resume_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_simple_cb_t cb): register a vCPU resume callback

Parameters

qemu_plugin_id_t id: plugin ID
qemu_plugin_vcpu_simple_cb_t cb: callback function

Description

The cb function is called every time a vCPU resumes execution.

type qemu_plugin_u64: uint64_t member of an entry in a scoreboard

Description

This field allows to access a specific uint64_t member in one given entry, located at a specified offset. Inline operations expect this as entry.

enum qemu_plugin_cb_flags: type of callback

Constants

QEMU_PLUGIN_CB_NO_REGS: callback does not access the CPU’s regs
QEMU_PLUGIN_CB_R_REGS: callback reads the CPU’s regs
QEMU_PLUGIN_CB_RW_REGS: callback reads and writes the CPU’s regs

Note

currently QEMU_PLUGIN_CB_RW_REGS is unused, plugins cannot change system register state.

enum qemu_plugin_cond: condition to enable callback

Constants

QEMU_PLUGIN_COND_NEVER: false
QEMU_PLUGIN_COND_ALWAYS: true
QEMU_PLUGIN_COND_EQ: is equal?
QEMU_PLUGIN_COND_NE: is not equal?
QEMU_PLUGIN_COND_LT: is less than?
QEMU_PLUGIN_COND_LE: is less than or equal?
QEMU_PLUGIN_COND_GT: is greater than?
QEMU_PLUGIN_COND_GE: is greater than or equal?

qemu_plugin_vcpu_tb_trans_cb_t: Typedef: translation callback

Syntax

void qemu_plugin_vcpu_tb_trans_cb_t (qemu_plugin_id_t id, struct qemu_plugin_tb *tb)

Parameters

qemu_plugin_id_t id: unique plugin id
struct qemu_plugin_tb *tb: opaque handle used for querying and instrumenting a block.

void qemu_plugin_register_vcpu_tb_trans_cb(qemu_plugin_id_t id, qemu_plugin_vcpu_tb_trans_cb_t cb): register a translate cb

Parameters

qemu_plugin_id_t id: plugin ID
qemu_plugin_vcpu_tb_trans_cb_t cb: callback function

Description

The cb function is called every time a translation occurs. The cb function is passed an opaque qemu_plugin_type which it can query for additional information including the list of translated instructions. At this point the plugin can register further callbacks to be triggered when the block or individual instruction executes.

void qemu_plugin_register_vcpu_tb_exec_cb(struct qemu_plugin_tb *tb, qemu_plugin_vcpu_udata_cb_t cb, enum qemu_plugin_cb_flags flags, void *userdata): register execution callback

Parameters

struct qemu_plugin_tb *tb: the opaque qemu_plugin_tb handle for the translation
qemu_plugin_vcpu_udata_cb_t cb: callback function
enum qemu_plugin_cb_flags flags: does the plugin read or write the CPU’s registers?
void *userdata: any plugin data to pass to the cb?

Description

The cb function is called every time a translated unit executes.

void qemu_plugin_register_vcpu_tb_exec_cond_cb(struct qemu_plugin_tb *tb, qemu_plugin_vcpu_udata_cb_t cb, enum qemu_plugin_cb_flags flags, enum qemu_plugin_cond cond, qemu_plugin_u64 entry, uint64_t imm, void *userdata): register conditional callback

Parameters

struct qemu_plugin_tb *tb: the opaque qemu_plugin_tb handle for the translation
qemu_plugin_vcpu_udata_cb_t cb: callback function
enum qemu_plugin_cb_flags flags: does the plugin read or write the CPU’s registers?
enum qemu_plugin_cond cond: condition to enable callback
qemu_plugin_u64 entry: first operand for condition
uint64_t imm: second operand for condition
void *userdata: any plugin data to pass to the cb?

Description

The cb function is called when a translated unit executes if entry cond imm is true. If condition is QEMU_PLUGIN_COND_ALWAYS, condition is never interpreted and this function is equivalent to qemu_plugin_register_vcpu_tb_exec_cb. If condition QEMU_PLUGIN_COND_NEVER, condition is never interpreted and callback is never installed.

enum qemu_plugin_op: describes an inline op

Constants

QEMU_PLUGIN_INLINE_ADD_U64: add an immediate value uint64_t
QEMU_PLUGIN_INLINE_STORE_U64: store an immediate value uint64_t

void qemu_plugin_register_vcpu_tb_exec_inline_per_vcpu(struct qemu_plugin_tb *tb, enum qemu_plugin_op op, qemu_plugin_u64 entry, uint64_t imm): execution inline op

Parameters

struct qemu_plugin_tb *tb: the opaque qemu_plugin_tb handle for the translation
enum qemu_plugin_op op: the type of qemu_plugin_op (e.g. ADD_U64)
qemu_plugin_u64 entry: entry to run op
uint64_t imm: the op data (e.g. 1)

Description

Insert an inline op on a given scoreboard entry.

void qemu_plugin_register_vcpu_insn_exec_cb(struct qemu_plugin_insn *insn, qemu_plugin_vcpu_udata_cb_t cb, enum qemu_plugin_cb_flags flags, void *userdata): register insn execution cb

Parameters

struct qemu_plugin_insn *insn: the opaque qemu_plugin_insn handle for an instruction
qemu_plugin_vcpu_udata_cb_t cb: callback function
enum qemu_plugin_cb_flags flags: does the plugin read or write the CPU’s registers?
void *userdata: any plugin data to pass to the cb?

Description

The cb function is called every time an instruction is executed

void qemu_plugin_register_vcpu_insn_exec_cond_cb(struct qemu_plugin_insn *insn, qemu_plugin_vcpu_udata_cb_t cb, enum qemu_plugin_cb_flags flags, enum qemu_plugin_cond cond, qemu_plugin_u64 entry, uint64_t imm, void *userdata): conditional insn execution cb

Parameters

struct qemu_plugin_insn *insn: the opaque qemu_plugin_insn handle for an instruction
qemu_plugin_vcpu_udata_cb_t cb: callback function
enum qemu_plugin_cb_flags flags: does the plugin read or write the CPU’s registers?
enum qemu_plugin_cond cond: condition to enable callback
qemu_plugin_u64 entry: first operand for condition
uint64_t imm: second operand for condition
void *userdata: any plugin data to pass to the cb?

Description

The cb function is called when an instruction executes if entry cond imm is true. If condition is QEMU_PLUGIN_COND_ALWAYS, condition is never interpreted and this function is equivalent to qemu_plugin_register_vcpu_insn_exec_cb. If condition QEMU_PLUGIN_COND_NEVER, condition is never interpreted and callback is never installed.

void qemu_plugin_register_vcpu_insn_exec_inline_per_vcpu(struct qemu_plugin_insn *insn, enum qemu_plugin_op op, qemu_plugin_u64 entry, uint64_t imm): insn exec inline op

Parameters

struct qemu_plugin_insn *insn: the opaque qemu_plugin_insn handle for an instruction
enum qemu_plugin_op op: the type of qemu_plugin_op (e.g. ADD_U64)
qemu_plugin_u64 entry: entry to run op
uint64_t imm: the op data (e.g. 1)

Description

Insert an inline op to every time an instruction executes.

size_t qemu_plugin_tb_n_insns(const struct qemu_plugin_tb *tb): query helper for number of insns in TB

Parameters

const struct qemu_plugin_tb *tb: opaque handle to TB passed to callback

Return

number of instructions in this block

uint64_t qemu_plugin_tb_vaddr(const struct qemu_plugin_tb *tb): query helper for vaddr of TB start

Parameters

const struct qemu_plugin_tb *tb: opaque handle to TB passed to callback

Return

virtual address of block start

struct qemu_plugin_insn *qemu_plugin_tb_get_insn(const struct qemu_plugin_tb *tb, size_t idx): retrieve handle for instruction

Parameters

const struct qemu_plugin_tb *tb: opaque handle to TB passed to callback
size_t idx: instruction number, 0 indexed

Description

The returned handle can be used in follow up helper queries as well as when instrumenting an instruction. It is only valid for the lifetime of the callback.

Return

opaque handle to instruction

size_t qemu_plugin_insn_data(const struct qemu_plugin_insn *insn, void *dest, size_t len): copy instruction data

Parameters

const struct qemu_plugin_insn *insn: opaque instruction handle from qemu_plugin_tb_get_insn()
void *dest: destination into which data is copied
size_t len: length of dest

Description

Returns the number of bytes copied, minimum of len and insn size.

size_t qemu_plugin_insn_size(const struct qemu_plugin_insn *insn): return size of instruction

Parameters

const struct qemu_plugin_insn *insn: opaque instruction handle from qemu_plugin_tb_get_insn()

Return

size of instruction in bytes

uint64_t qemu_plugin_insn_vaddr(const struct qemu_plugin_insn *insn): return vaddr of instruction

Parameters

const struct qemu_plugin_insn *insn: opaque instruction handle from qemu_plugin_tb_get_insn()

Return

virtual address of instruction

void *qemu_plugin_insn_haddr(const struct qemu_plugin_insn *insn): return hardware addr of instruction

Parameters

const struct qemu_plugin_insn *insn: opaque instruction handle from qemu_plugin_tb_get_insn()

Return

hardware (physical) target address of instruction

type qemu_plugin_meminfo_t: opaque memory transaction handle

Description

This can be further queried using the qemu_plugin_mem_* query functions.

unsigned int qemu_plugin_mem_size_shift(qemu_plugin_meminfo_t info): get size of access

Parameters

qemu_plugin_meminfo_t info: opaque memory transaction handle

Return

size of access in ^2 (0=byte, 1=16bit, 2=32bit etc…)

bool qemu_plugin_mem_is_sign_extended(qemu_plugin_meminfo_t info): was the access sign extended

Parameters

qemu_plugin_meminfo_t info: opaque memory transaction handle

Return

true if it was, otherwise false

bool qemu_plugin_mem_is_big_endian(qemu_plugin_meminfo_t info): was the access big endian

Parameters

qemu_plugin_meminfo_t info: opaque memory transaction handle

Return

true if it was, otherwise false

bool qemu_plugin_mem_is_store(qemu_plugin_meminfo_t info): was the access a store

Parameters

qemu_plugin_meminfo_t info: opaque memory transaction handle

Return

true if it was, otherwise false

struct qemu_plugin_hwaddr *qemu_plugin_get_hwaddr(qemu_plugin_meminfo_t info, uint64_t vaddr): return handle for memory operation

Parameters

qemu_plugin_meminfo_t info: opaque memory info structure
uint64_t vaddr: the virtual address of the memory operation

Description

For system emulation returns a qemu_plugin_hwaddr handle to query details about the actual physical address backing the virtual address. For linux-user guests it just returns NULL.

This handle is only valid for the duration of the callback. Any information about the handle should be recovered before the callback returns.

bool qemu_plugin_hwaddr_is_io(const struct qemu_plugin_hwaddr *haddr): query whether memory operation is IO

Parameters

const struct qemu_plugin_hwaddr *haddr: address handle from qemu_plugin_get_hwaddr()

Description

Returns true if the handle’s memory operation is to memory-mapped IO, or false if it is to RAM

uint64_t qemu_plugin_hwaddr_phys_addr(const struct qemu_plugin_hwaddr *haddr): query physical address for memory operation

Parameters

const struct qemu_plugin_hwaddr *haddr: address handle from qemu_plugin_get_hwaddr()

Description

Returns the physical address associated with the memory operation

Note that the returned physical address may not be unique if you are dealing with multiple address spaces.

qemu_plugin_vcpu_mem_cb_t: Typedef: memory callback function type

Syntax

void qemu_plugin_vcpu_mem_cb_t (unsigned int vcpu_index, qemu_plugin_meminfo_t info, uint64_t vaddr, void *userdata)

Parameters

unsigned int vcpu_index: the executing vCPU
qemu_plugin_meminfo_t info: an opaque handle for further queries about the memory
uint64_t vaddr: the virtual address of the transaction
void *userdata: any user data attached to the callback

void qemu_plugin_register_vcpu_mem_cb(struct qemu_plugin_insn *insn, qemu_plugin_vcpu_mem_cb_t cb, enum qemu_plugin_cb_flags flags, enum qemu_plugin_mem_rw rw, void *userdata): register memory access callback

Parameters

struct qemu_plugin_insn *insn: handle for instruction to instrument
qemu_plugin_vcpu_mem_cb_t cb: callback of type qemu_plugin_vcpu_mem_cb_t
enum qemu_plugin_cb_flags flags: (currently unused) callback flags
enum qemu_plugin_mem_rw rw: monitor reads, writes or both
void *userdata: opaque pointer for userdata

Description

This registers a full callback for every memory access generated by an instruction. If the instruction doesn’t access memory no callback will be made.

The callback reports the vCPU the access took place on, the virtual address of the access and a handle for further queries. The user can attach some userdata to the callback for additional purposes.

Other execution threads will continue to execute during the callback so the plugin is responsible for ensuring it doesn’t get confused by making appropriate use of locking if required.

void qemu_plugin_register_vcpu_mem_inline_per_vcpu(struct qemu_plugin_insn *insn, enum qemu_plugin_mem_rw rw, enum qemu_plugin_op op, qemu_plugin_u64 entry, uint64_t imm): inline op for mem access

Parameters

struct qemu_plugin_insn *insn: handle for instruction to instrument
enum qemu_plugin_mem_rw rw: apply to reads, writes or both
enum qemu_plugin_op op: the op, of type qemu_plugin_op
qemu_plugin_u64 entry: entry to run op
uint64_t imm: immediate data for op

Description

This registers a inline op every memory access generated by the instruction.

const void *qemu_plugin_request_time_control(void): request the ability to control time

Parameters

void: no arguments

Description

This grants the plugin the ability to control system time. Only one plugin can control time so if multiple plugins request the ability all but the first will fail.

Returns an opaque handle or NULL if fails

void qemu_plugin_update_ns(const void *handle, int64_t time): update system emulation time

Parameters

const void *handle: opaque handle returned by qemu_plugin_request_time_control()
int64_t time: time in nanoseconds

Description

This allows an appropriately authorised plugin (i.e. holding the time control handle) to move system time forward to time. For user-mode emulation the time is not changed by this as all reported time comes from the host kernel.

Start time is 0.

char *qemu_plugin_insn_disas(const struct qemu_plugin_insn *insn): return disassembly string for instruction

Parameters

const struct qemu_plugin_insn *insn: instruction reference

Description

Returns an allocated string containing the disassembly

const char *qemu_plugin_insn_symbol(const struct qemu_plugin_insn *insn): best effort symbol lookup

Parameters

const struct qemu_plugin_insn *insn: instruction reference

Description

Return a static string referring to the symbol. This is dependent on the binary QEMU is running having provided a symbol table.

void qemu_plugin_vcpu_for_each(qemu_plugin_id_t id, qemu_plugin_vcpu_simple_cb_t cb): iterate over the existing vCPU

Parameters

qemu_plugin_id_t id: plugin ID
qemu_plugin_vcpu_simple_cb_t cb: callback function

Description

The cb function is called once for each existing vCPU.

See also: qemu_plugin_register_vcpu_init_cb()

void qemu_plugin_register_atexit_cb(qemu_plugin_id_t id, qemu_plugin_udata_cb_t cb, void *userdata): register exit callback

Parameters

qemu_plugin_id_t id: plugin ID
qemu_plugin_udata_cb_t cb: callback
void *userdata: user data for callback

Description

The cb function is called once execution has finished. Plugins should be able to free all their resources at this point much like after a reset/uninstall callback is called.

In user-mode it is possible a few un-instrumented instructions from child threads may run before the host kernel reaps the threads.

void qemu_plugin_outs(const char *string): output string via QEMU’s logging system

Parameters

const char *string: a string

bool qemu_plugin_bool_parse(const char *name, const char *val, bool *ret): parses a boolean argument in the form of “<argname>=[on|yes|true|off|no|false]”

Parameters

const char *name: argument name, the part before the equals sign
const char *val: argument value, what’s after the equals sign
bool *ret: output return value

Description

returns true if the combination name**=**val parses correctly to a boolean argument, and false otherwise

const char *qemu_plugin_path_to_binary(void): path to binary file being executed

Parameters

void: no arguments

Description

Return a string representing the path to the binary. For user-mode this is the main executable. For system emulation we currently return NULL. The user should g_free() the string once no longer needed.

uint64_t qemu_plugin_start_code(void): returns start of text segment

Parameters

void: no arguments

Description

Returns the nominal start address of the main text segment in user-mode. Currently returns 0 for system emulation.

uint64_t qemu_plugin_end_code(void): returns end of text segment

Parameters

void: no arguments

Description

Returns the nominal end address of the main text segment in user-mode. Currently returns 0 for system emulation.

uint64_t qemu_plugin_entry_code(void): returns start address for module

Parameters

void: no arguments

Description

Returns the nominal entry address of the main text segment in user-mode. Currently returns 0 for system emulation.

type qemu_plugin_reg_descriptor: register descriptions

GArray *qemu_plugin_get_registers(void): return register list for current vCPU

Parameters

void: no arguments

Description

Returns a potentially empty GArray of qemu_plugin_reg_descriptor. Caller frees the array (but not the const strings).

Should be used from a qemu_plugin_register_vcpu_init_cb() callback after the vCPU is initialised, i.e. in the vCPU context.

int qemu_plugin_read_register(struct qemu_plugin_register *handle, GByteArray *buf): read register for current vCPU

Parameters

struct qemu_plugin_register *handle: a qemu_plugin_reg_handle handle
GByteArray *buf: A GByteArray for the data owned by the plugin

Description

This function is only available in a context that register read access is explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag.

Returns the size of the read register. The content of buf is in target byte order. On failure returns -1.

struct qemu_plugin_scoreboard *qemu_plugin_scoreboard_new(size_t element_size): alloc a new scoreboard

Parameters

size_t element_size: size (in bytes) for one entry

Description

Returns a pointer to a new scoreboard. It must be freed using qemu_plugin_scoreboard_free.

void qemu_plugin_scoreboard_free(struct qemu_plugin_scoreboard *score): free a scoreboard

Parameters

struct qemu_plugin_scoreboard *score: scoreboard to free

void *qemu_plugin_scoreboard_find(struct qemu_plugin_scoreboard *score, unsigned int vcpu_index): get pointer to an entry of a scoreboard

Parameters

struct qemu_plugin_scoreboard *score: scoreboard to query
unsigned int vcpu_index: entry index

Description

Returns address of entry of a scoreboard matching a given vcpu_index. This address can be modified later if scoreboard is resized.

void qemu_plugin_u64_add(qemu_plugin_u64 entry, unsigned int vcpu_index, uint64_t added): add a value to a qemu_plugin_u64 for a given vcpu

Parameters

qemu_plugin_u64 entry: entry to query
unsigned int vcpu_index: entry index
uint64_t added: value to add

uint64_t qemu_plugin_u64_get(qemu_plugin_u64 entry, unsigned int vcpu_index): get value of a qemu_plugin_u64 for a given vcpu

Parameters

qemu_plugin_u64 entry: entry to query
unsigned int vcpu_index: entry index

void qemu_plugin_u64_set(qemu_plugin_u64 entry, unsigned int vcpu_index, uint64_t val): set value of a qemu_plugin_u64 for a given vcpu

Parameters

qemu_plugin_u64 entry: entry to query
unsigned int vcpu_index: entry index
uint64_t val: new value

uint64_t qemu_plugin_u64_sum(qemu_plugin_u64 entry): return sum of all vcpu entries in a scoreboard

Parameters

qemu_plugin_u64 entry: entry to sum