QEMU TCG Plugins — QEMU documentation

# QEMU TCG Plugins

## 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 inline instructions doing various operations, like adding or storing an immediate value. It is also possible to execute a callback conditionally, with condition being evaluated inline. All those inline operations are associated to a `scoreboard`, which is a thread-local storage automatically expanded when new cores/threads are created and that can be accessed/modified in a thread-safe way without any lock needed. Combining inline operations and conditional callbacks offer a more efficient way to instrument binaries, compared to classic callbacks.

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.

# 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.

enum qemu_plugin_discon_type

  type of a (potential) PC discontinuity

Constants

`QEMU_PLUGIN_DISCON_INTERRUPT`

  an interrupt, defined across all architectures as an asynchronous event, usually originating from outside the CPU

`QEMU_PLUGIN_DISCON_EXCEPTION`

  an exception, defined across all architectures as a synchronous event in response to a specific instruction being executed

`QEMU_PLUGIN_DISCON_HOSTCALL`

  a host call, functionally a special kind of exception that is not handled by code run by the vCPU but machinery outside the vCPU

`QEMU_PLUGIN_DISCON_ALL`

  all types of disconinuity events currently covered

qemu_plugin_vcpu_discon_cb_t

  Typedef: vcpu discontinuity callback

Syntax

> `void qemu_plugin_vcpu_discon_cb_t (qemu_plugin_id_t id, unsigned int vcpu_index, enum qemu_plugin_discon_type type, uint64_t from_pc, uint64_t to_pc)`

Parameters

`qemu_plugin_id_t id`

  plugin ID

`unsigned int vcpu_index`

  the current vcpu context

`enum qemu_plugin_discon_type type`

  the type of discontinuity

`uint64_t from_pc`

  the source of the discontinuity, e.g. the PC before the transition

`uint64_t to_pc`

  the PC pointing to the next instruction to be executed

Description

The exact semantics of from_pc depends on the type of discontinuity. For interrupts, from_pc will point to the next instruction which would have been executed. For exceptions and host calls, from_pc will point to the instruction that caused the exception or issued the host call. Note that in the case of exceptions, the instruction may not be retired and thus not observable via general instruction exec callbacks. The same may be the case for some host calls such as hypervisor call “exceptions”.

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.

void qemu_plugin_register_vcpu_discon_cb(qemu_plugin_id_t id, enum qemu_plugin_discon_type type, qemu_plugin_vcpu_discon_cb_t cb)

  register a discontinuity callback

Parameters

`qemu_plugin_id_t id`

  plugin ID

`enum qemu_plugin_discon_type type`

  types of discontinuities for which to call the callback

`qemu_plugin_vcpu_discon_cb_t cb`

  callback function

Description

The cb function is called every time a vCPU receives a discontinuity event of the specified type(s), after the vCPU was prepared to handle the event. Preparation entails updating the PC, usually to some interrupt handler or trap vector entry.

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

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

qemu_plugin_mem_value qemu_plugin_mem_get_value(qemu_plugin_meminfo_t info)

  return last value loaded/stored

Parameters

`qemu_plugin_meminfo_t info`

  opaque memory transaction handle

Return

memory value

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, if called inside a callback that can be registered with a qemu_plugin_cb_flags argument. This function can also be used in any callback context that does not use a flags argument, such as in a callback registered with qemu_plugin_register_vcpu_init_cb(), except for callbacks registered with qemu_plugin_register_atexit_cb() and qemu_plugin_register_flush_cb().

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

int qemu_plugin_write_register(struct qemu_plugin_register *handle, GByteArray *buf)

  write 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_RW_REGS flag, if called inside a callback that can be registered with a qemu_plugin_cb_flags argument. This function can also be used in any callback context that does not use a flags argument, such as in a callback registered with qemu_plugin_register_vcpu_init_cb(), except for callbacks registered with qemu_plugin_register_atexit_cb() and qemu_plugin_register_flush_cb().

The size of buf must be at least the size of the requested register. Attempting to write a register with buf smaller than the register size will result in a crash or other undesired behavior.

Returns the number of bytes written. On failure returns 0.

bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len)

  read from memory using a virtual address

Parameters

`uint64_t addr`

  A virtual address to read from

`GByteArray *data`

  A byte array to store data into

`size_t len`

  The number of bytes to read, starting from addr

Description

len bytes of data is read starting at addr and stored into data. If data is not large enough to hold len bytes, it will be expanded to the necessary size, reallocating if necessary. len must be greater than 0.

This function does not ensure writes are flushed prior to reading, so callers should take care when calling this function in plugin callbacks to avoid attempting to read data which may not yet be written and should use the memory callback API instead.

Returns true on success and false on failure.

bool qemu_plugin_write_memory_vaddr(uint64_t addr, GByteArray *data)

  write to memory using a virtual address

Parameters

`uint64_t addr`

  A virtual address to write to

`GByteArray *data`

  A byte array containing the data to write

Description

The contents of data will be written to memory starting at the virtual address addr.

This function does not guarantee consistency of writes, nor does it ensure that pending writes are flushed either before or after the write takes place, so callers should take care to only call this function in vCPU context (i.e. in callbacks) and avoid depending on the existence of data written using this function which may be overwritten afterward.

Returns true on success and false on failure.

enum qemu_plugin_hwaddr_operation_result

  result of a memory operation

Constants

`QEMU_PLUGIN_HWADDR_OPERATION_OK`

  hwaddr operation succeeded

`QEMU_PLUGIN_HWADDR_OPERATION_ERROR`

  unexpected error occurred

`QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR`

  error in memory device

`QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED`

  permission error

`QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS`

  address was invalid

`QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE`

  invalid address space

enum qemu_plugin_hwaddr_operation_result qemu_plugin_read_memory_hwaddr(uint64_t addr, GByteArray *data, size_t len)

  read from memory using a hardware address

Parameters

`uint64_t addr`

  The physical address to read from

`GByteArray *data`

  A byte array to store data into

`size_t len`

  The number of bytes to read, starting from addr

Description

len bytes of data is read from the current memory space for the current vCPU starting at addr and stored into data. If data is not large enough to hold len bytes, it will be expanded to the necessary size, reallocating if necessary. len must be greater than 0.

This function does not ensure writes are flushed prior to reading, so callers should take care when calling this function in plugin callbacks to avoid attempting to read data which may not yet be written and should use the memory callback API instead.

This function is only valid for softmmu targets.

Returns a qemu_plugin_hwaddr_operation_result indicating the result of the operation.

enum qemu_plugin_hwaddr_operation_result qemu_plugin_write_memory_hwaddr(uint64_t addr, GByteArray *data)

  write to memory using a hardware address

Parameters

`uint64_t addr`

  A physical address to write to

`GByteArray *data`

  A byte array containing the data to write

Description

The contents of data will be written to memory starting at the hardware address addr in the current address space for the current vCPU.

This function does not guarantee consistency of writes, nor does it ensure that pending writes are flushed either before or after the write takes place, so callers should take care when calling this function in plugin callbacks to avoid depending on the existence of data written using this function which may be overwritten afterward. In addition, this function requires that the pages containing the address are not locked. Practically, this means that you should not write instruction memory in a current translation block inside a callback registered with qemu_plugin_register_vcpu_tb_trans_cb.

You can, for example, write instruction memory in a current translation block in a callback registered with qemu_plugin_register_vcpu_tb_exec_cb, although be aware that the write will not be flushed until after the translation block has finished executing. In general, this function should be used to write data memory or to patch code at a known address, not in a current translation block.

This function is only valid for softmmu targets.

Returns a qemu_plugin_hwaddr_operation_result indicating the result of the operation.

bool qemu_plugin_translate_vaddr(uint64_t vaddr, uint64_t *hwaddr)

  translate virtual address for current vCPU

Parameters

`uint64_t vaddr`

  virtual address to translate

`uint64_t *hwaddr`

  pointer to store the physical address

Description

This function is only valid in vCPU context (i.e. in callbacks) and is only valid for softmmu targets.

Returns true on success and false on failure.

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