zx_object_get_info

Summary

Query information about an object.

Declaration

#include <zircon/syscalls.h>

zx_status_t zx_object_get_info(zx_handle_t handle,
                               uint32_t topic,
                               void* buffer,
                               size_t buffer_size,
                               size_t* actual,
                               size_t* avail);

Description

zx_object_get_info() requests information about the provided handle (or the object the handle refers to). The topic parameter indicates what specific information is desired.

buffer is a pointer to a buffer of size buffer_size to return the information.

actual is an optional pointer to return the number of records that were written to buffer.

avail is an optional pointer to return the number of records that are available to read.

If the buffer is insufficiently large, avail will be larger than actual.

TOPICS

ZX_INFO_HANDLE_VALID

handle type: Any

buffer type: n/a

Returns ZX_OK if handle is valid, or ZX_ERR_BAD_HANDLE otherwise. No records are returned and buffer may be NULL.

ZX_INFO_HANDLE_BASIC

handle type: Any

buffer type: zx_info_handle_basic_t[1]

typedef struct zx_info_handle_basic {
    // The unique id assigned by kernel to the object referenced by the
    // handle.
    zx_koid_t koid;

    // The immutable rights assigned to the handle. Two handles that
    // have the same koid and the same rights are equivalent and
    // interchangeable.
    zx_rights_t rights;

    // The object type: channel, event, socket, etc.
    uint32_t type;                // zx_obj_type_t;

    // If the object referenced by the handle is related to another (such
    // as the other end of a channel, or the parent of a job) then
    // |related_koid| is the koid of that object, otherwise it is zero.
    // This relationship is immutable: an object's |related_koid| does
    // not change even if the related object no longer exists.
    zx_koid_t related_koid;
} zx_info_handle_basic_t;

ZX_INFO_HANDLE_COUNT

handle type: Any

buffer type: zx_info_handle_count_t[1]

typedef struct zx_info_handle_count {
    // The number of outstanding handles to a kernel object.
    uint32_t handle_count;
} zx_info_handle_count_t;

The handle_count should only be used as a debugging aid. Do not use it to check that an untrusted processes cannot modify a kernel object. Due to asynchronous nature of the system scheduler, there might be a time window during which it is possible for an object to be modified by a previous handle owner even as the last handle is transferred from one process to another.

ZX_INFO_PROCESS_HANDLE_STATS

handle type: Process

buffer type: zx_info_process_handle_stats_t[1]

typedef struct zx_info_process_handle_stats {
    // The number of outstanding handles to kernel objects of each type.
    uint32_t handle_count[ZX_OBJ_TYPE_UPPER_BOUND];
} zx_info_process_handle_stats_t;

ZX_INFO_HANDLE_TABLE

handle type: Process

buffer type: zx_info_handle_extended_t[n]

Returns an array of zx_info_handle_extended_t one for each handle in the Process at the moment of the call. The kernel ensures that the handles returned are consistent.

typedef struct zx_info_handle_extended {
    // The object type: channel, event, socket, etc.
    zx_obj_type_t type;

    // The handle value, which is only valid for the process that
    // was passed to ZX_INFO_HANDLE_TABLE.
    zx_handle_t handle_value;

    // The immutable rights assigned to the handle. Two handles that
    // have the same koid and the same rights are equivalent and
    // interchangeable.
    zx_rights_t rights;

    uint32_t reserved;

    // The unique id assigned by kernel to the object referenced by the
    // handle.
    zx_koid_t koid;

    // If the object referenced by the handle is related to another (such
    // as the other end of a channel, or the parent of a job) then
    // |related_koid| is the koid of that object, otherwise it is zero.
    // This relationship is immutable: an object's |related_koid| does
    // not change even if the related object no longer exists.
    zx_koid_t related_koid;

    // If the object referenced by the handle has a peer, like the
    // other end of a channel, then this is the koid of the process
    // which currently owns it.
    zx_koid_t peer_owner_koid;
} zx_info_handle_extended_t;

Note that a process might have live references to objects for which the process does not have a handle to. For example, running threads for which all handles have been closed.

ZX_INFO_JOB

handle type: Job

buffer type: zx_info_job_t[1]

typedef struct zx_info_job {
    // The job's return code; only valid if |exited| is true.
    // If the job was killed, it will be one of the ZX_TASK_RETCODE values.
    int64_t return_code;

    // If true, the job has exited and |return_code| is valid.
    bool exited;

    // True if the ZX_PROP_JOB_KILL_ON_OOM property was set.
    bool kill_on_oom;

    // True if a debugger is attached to the job.
    bool debugger_attached;
} zx_info_job_t;

Note that |exited| will immediately report that the job has exited following a |zx_task_kill| or equivalent (e.g. an OOM kill), but child jobs and processes may still be in the process of exiting.

ZX_INFO_PROCESS

handle type: Process

buffer type: zx_info_process_t[1]

typedef struct zx_info_process {
    // The process's return code; only valid if the
    // |ZX_PROCESS_INFO_FLAG_EXITED| flag is set. If the process was killed, it
    // will be one of the |ZX_TASK_RETCODE| values.
    int64_t return_code;

    // The monotonic time at which `zx_process_start()` was called, only valid
    // if the |ZX_INFO_PROCESS_FLAG_STARTED| flag is set.
    zx_time_t start_time;

    // Bitwise OR of ZX_INFO_PROCESS_FLAG_* values.
    uint32_t flags;
} zx_info_process_t;

Note that |flags| will immediately report that the process has exited (i.e. it will contain ZX_INFO_PROCESS_FLAG_EXITED) following a |zx_task_kill|, but child threads may still be in the process of exiting.

ZX_INFO_PROCESS_THREADS

handle type: Process

buffer type: zx_koid_t[n]

Returns an array of zx_koid_t, one for each running thread in the Process at that moment in time.

N.B. Getting the list of threads is inherently racy. This can be somewhat mitigated by first suspending all the threads, but note that an external thread can create new threads. actual will contain the number of threads returned in buffer. avail will contain the total number of threads of the process at the time the list of threads was obtained, it could be larger than actual.

ZX_INFO_THREAD

handle type: Thread

buffer type: zx_info_thread_t[1]

typedef struct zx_info_thread {
    // One of ZX_THREAD_STATE_* values.
    uint32_t state;

    // If |state| is ZX_THREAD_STATE_BLOCKED_EXCEPTION, the thread has gotten
    // an exception and is waiting for the exception to be handled by the
    // specified channel.
    // The value is one of ZX_EXCEPTION_CHANNEL_TYPE_*.
    uint32_t wait_exception_channel_type;

    // CPUs this thread may be scheduled on, as specified by
    // a profile object applied to this thread.
    //
    // The kernel may not internally store invalid CPUs in the mask, so
    // this may not exactly match the mask applied to the thread for
    // CPUs beyond what the system is able to use.
    zx_cpu_set_t cpu_affinity_mask;
} zx_info_thread_t;

The values in this struct are mainly for informational and debugging purposes at the moment.

The various ZX_THREAD_STATE_ values are defined by

#include <zircon/syscalls/object.h>
  • ZX_THREAD_STATE_NEW: The thread has been created but it has not started running yet.
  • ZX_THREAD_STATE_RUNNING: The thread is running user code normally.
  • ZX_THREAD_STATE_SUSPENDED: Stopped due to zx_task_suspend().
  • ZX_THREAD_STATE_BLOCKED: In a syscall or handling an exception. This value is never returned by itself. See ZX_THREAD_STATE_BLOCKED_* below.
  • ZX_THREAD_STATE_DYING: The thread is in the process of being terminated, but it has not been stopped yet.
  • ZX_THREAD_STATE_DEAD: The thread has stopped running.

When a thread is stopped inside a blocking syscall, or stopped in an exception, the value returned in state is one of the following:

  • ZX_THREAD_STATE_BLOCKED_EXCEPTION: The thread is stopped in an exception.
  • ZX_THREAD_STATE_BLOCKED_SLEEPING: The thread is stopped in zx_nanosleep().
  • ZX_THREAD_STATE_BLOCKED_FUTEX: The thread is stopped in zx_futex_wait().
  • ZX_THREAD_STATE_BLOCKED_PORT: The thread is stopped in zx_port_wait().
  • ZX_THREAD_STATE_BLOCKED_CHANNEL: The thread is stopped in zx_channel_call().
  • ZX_THREAD_STATE_BLOCKED_WAIT_ONE: The thread is stopped in zx_object_wait_one().
  • ZX_THREAD_STATE_BLOCKED_WAIT_MANY: The thread is stopped in zx_object_wait_many().
  • ZX_THREAD_STATE_BLOCKED_INTERRUPT: The thread is stopped in zx_interrupt_wait().

The various ZX_EXCEPTION_CHANNEL_TYPE_ values are defined by

#include <zircon/syscalls/exception.h>
  • ZX_EXCEPTION_CHANNEL_TYPE_NONE
  • ZX_EXCEPTION_CHANNEL_TYPE_DEBUGGER
  • ZX_EXCEPTION_CHANNEL_TYPE_THREAD
  • ZX_EXCEPTION_CHANNEL_TYPE_PROCESS
  • ZX_EXCEPTION_CHANNEL_TYPE_JOB
  • ZX_EXCEPTION_CHANNEL_TYPE_JOB_DEBUGGER

ZX_INFO_THREAD_EXCEPTION_REPORT

handle type: Thread

buffer type: zx_exception_report_t[1]

#include <zircon/syscalls/exception.h>

If the thread is currently in an exception and is waiting for an exception response, then this returns the exception report as a single zx_exception_report_t, with status ZX_OK.

Returns ZX_ERR_BAD_STATE if the thread is not in an exception and waiting for an exception response.

ZX_INFO_THREAD_STATS

handle type: Thread

buffer type: zx_info_thread_stats[1]

typedef struct zx_info_thread_stats {
    // Total accumulated running time of the thread.
    //
    // Note: See zx_info_task_runtime for queue time in addition to runtime.
    zx_duration_t total_runtime;

    // CPU number that this thread was last scheduled on, or ZX_INFO_INVALID_CPU
    // if the thread has never been scheduled on a CPU. By the time this call
    // returns, the thread may have been scheduled elsewhere, so this
    // information should only be used as a hint or for statistics.
    uint32_t last_scheduled_cpu;
} zx_info_thread_stats_t;

Returns ZX_ERR_BAD_STATE if the thread has exited.

ZX_INFO_GUEST_STATS

handle type: Resource (Specifically, the info resource)

buffer type: zx_info_guest_stats_t[1]

// Each machine has its own format for the same ZX_INFO_GUEST_STATS topic.
// In each build, zx_info_guest_stats_t is a typedef alias for the type.
// Cross-tools can select the machine-specific type to use based on the
// source of the data they are working with.
typedef struct zx_arm64_info_guest_stats {
    uint32_t cpu_number;
    uint32_t flags;
    uint64_t vm_entries;
    uint64_t vm_exits;
    uint64_t wfi_wfe_instructions;
    uint64_t instruction_aborts;
    uint64_t data_aborts;
    uint64_t system_instructions;
    uint64_t smc_instructions;
    uint64_t interrupts;
} zx_arm64_info_guest_stats_t;

typedef struct zx_x86_64_info_guest_stats {
    uint32_t cpu_number;
    uint32_t flags;
    uint64_t vm_entries;
    uint64_t vm_exits;
    uint64_t interrupts;
    uint64_t interrupt_windows;
    uint64_t cpuid_instructions;
    uint64_t hlt_instructions;
    uint64_t control_register_accesses;
    uint64_t io_instructions;
    uint64_t rdmsr_instructions;
    uint64_t wrmsr_instructions;
    uint64_t ept_violations;
    uint64_t xsetbv_instructions;
    uint64_t pause_instructions;
    uint64_t vmcall_instructions;
} zx_x86_64_info_guest_stats;

ZX_INFO_CPU_STATS

Note: many values of this topic are being retired in favor of a different mechanism.

handle type: Resource (Specifically, the info resource)

buffer type: zx_info_cpu_stats_t[1]

typedef struct zx_info_cpu_stats {
    uint32_t cpu_number;
    uint32_t flags;

    zx_duration_t idle_time;

    // kernel scheduler counters
    uint64_t reschedules;
    uint64_t context_switches;
    uint64_t irq_preempts;
    uint64_t preempts;
    uint64_t yields;

    // cpu level interrupts and exceptions
    uint64_t ints;          // hardware interrupts, minus timer interrupts
                            // inter-processor interrupts
    uint64_t timer_ints;    // timer interrupts
    uint64_t timers;        // timer callbacks
    uint64_t page_faults;   // (deprecated, returns 0)
    uint64_t exceptions;    // (deprecated, returns 0)
    uint64_t syscalls;

    // inter-processor interrupts
    uint64_t reschedule_ipis;
    uint64_t generic_ipis;
} zx_info_cpu_stats_t;

ZX_INFO_VMAR

handle type: VM Address Region

buffer type: zx_info_vmar_t[1]

typedef struct zx_info_vmar {
    // Base address of the region.
    uintptr_t base;

    // Length of the region, in bytes.
    size_t len;
} zx_info_vmar_t;

This returns a single zx_info_vmar_t that describes the range of address space that the VMAR occupies.

ZX_INFO_VMO

handle type: VM Object

buffer type: zx_info_vmo_t[1]

typedef struct zx_info_vmo {
    // The koid of this VMO.
    zx_koid_t koid;

    // The name of this VMO.
    char name[ZX_MAX_NAME_LEN];

    // The size of this VMO.
    uint64_t size_bytes;

    // If this VMO is a child, the koid of its parent. Otherwise, zero.
    zx_koid_t parent_koid;

    // The number of children of this VMO, if any.
    size_t num_children;

    // The number of times this VMO is currently mapped into VMARs.
    size_t num_mappings;

    // An estimate of the number of unique address spaces that
    // this VMO is mapped into.
    size_t share_count;

    // Bitwise OR of ZX_INFO_VMO_* values.
    uint32_t flags;

    // If |ZX_INFO_VMO_TYPE(flags) == ZX_INFO_VMO_TYPE_PAGED|, the amount of
    // memory currently allocated to this VMO.
    uint64_t committed_bytes;

    // If |flags & ZX_INFO_VMO_VIA_HANDLE|, the handle rights.
    // If |flags & ZX_INFO_VMO_VIA_IOB_HANDLE|, the handle rights of the
    // containing IOB.
    // Undefined otherwise.
    zx_rights_t handle_rights;

    // VMO mapping cache policy. One of ZX_CACHE_POLICY_*
    uint32_t cache_policy;

    // Amount of kernel memory, in bytes, allocated to track metadata
    // associated with this VMO.
    uint64_t metadata_bytes;

    // Running counter of the number of times the kernel, without user request,
    // performed actions on this VMO that would have caused |committed_bytes| to
    // report a different value.
    uint64_t committed_change_events;
} zx_info_vmo_t;

This returns a single zx_info_vmo_t that describes various attributes of the VMO.

ZX_INFO_SOCKET

handle type: Socket

buffer type: zx_info_socket_t[1]

typedef struct zx_info_socket {
    // The options passed to zx_socket_create().
    uint32_t options;

    // The maximum size of the receive buffer of a socket, in bytes.
    //
    // The receive buffer may become full at a capacity less than the maximum
    // due to overhead.
    size_t rx_buf_max;

    // The size of the receive buffer of a socket, in bytes.
    size_t rx_buf_size;

    // The amount of data, in bytes, that is available for reading in a single
    // zx_socket_read call.
    //
    // For stream sockets, this value will match |rx_buf_size|. For datagram
    // sockets, this value will be the size of the next datagram in the receive
    // buffer.
    size_t rx_buf_available;

    // The maximum size of the transmit buffer of a socket, in bytes.
    //
    // The transmit buffer may become full at a capacity less than the maximum
    // due to overhead.
    //
    // Will be zero if the peer endpoint is closed.
    size_t tx_buf_max;

    // The size of the transmit buffer of a socket, in bytes.
    //
    // Will be zero if the peer endpoint is closed.
    size_t tx_buf_size;
} zx_info_socket_t;

ZX_INFO_TIMER

handle type: Timer

buffer type: zx_info_timer_t[1]

typedef struct zx_info_timer {
    // The options passed to zx_timer_create().
    uint32_t options;

    // The deadline with respect to ZX_CLOCK_MONOTONIC at which the timer will
    // fire next.
    //
    // This value will be zero if the timer is not set to fire.
    zx_time_t deadline;

    // Specifies a range from deadline - slack to deadline + slack during which
    // the timer is allowed to fire. The system uses this parameter as a hint to
    // coalesce nearby timers.
    //
    // The precise coalescing behavior is controlled by the options parameter
    // specified when the timer was created.
    //
    // This value will be zero if the timer is not set to fire.
    zx_duration_t slack;
} zx_info_timer_t;

ZX_INFO_JOB_CHILDREN

handle type: Job

buffer type: zx_koid_t[n]

Returns an array of zx_koid_t, one for each direct child Job of the provided Job handle.

ZX_INFO_JOB_PROCESSES

handle type: Job

buffer type: zx_koid_t[n]

Returns an array of zx_koid_t, one for each direct child Process of the provided Job handle.

ZX_INFO_TASK_STATS

handle type: Process

buffer type: zx_info_task_stats_t[1]

Returns statistics about resources (e.g., memory) used by a task.

typedef struct zx_info_task_stats {
    // The total size of mapped memory ranges in the task.
    // Not all will be backed by physical memory.
    size_t mem_mapped_bytes;

    // For the fields below, a byte is considered committed if it's backed by
    // physical memory. Some of the memory may be double-mapped, and thus
    // double-counted.

    // Committed memory that is only mapped into this task.
    size_t mem_private_bytes;

    // Committed memory that is mapped into this and at least one other task.
    size_t mem_shared_bytes;

    // A number that estimates the fraction of mem_shared_bytes that this
    // task is responsible for keeping alive.
    //
    // An estimate of:
    //   For each shared, committed byte:
    //   mem_scaled_shared_bytes += 1 / (number of tasks mapping this byte)
    //
    // This number is strictly smaller than mem_shared_bytes.
    size_t mem_scaled_shared_bytes;
} zx_info_task_stats_t;

Additional errors:

  • ZX_ERR_BAD_STATE: If the target process has terminated

ZX_INFO_TASK_RUNTIME

handle type: Job, Process, or Thread

buffer type: zx_info_task_runtime_t[1]

Returns statistics about the runtime of a task.

// Info on the runtime of a task.
typedef struct zx_info_task_runtime {
    // The total amount of time this task and its children were
    // running on a CPU (not blocked).
    // * Threads include only their own runtime.
    // * Processes include the runtime for all of their threads (including threads that previously
    // exited).
    // * Jobs include the runtime for all of their processes (including processes that previously
    // exited).
    zx_duration_t cpu_time;

    // The total amount of time this task and its children were queued
    // to run (ready) but not actually using a CPU.
    // * Threads include only their own queue time.
    // * Processes include the queue time for all of their threads (including threads that
    // previously exited).
    // * Jobs include the queue time for all of their processes (including processes that previously
    // exited).
    zx_duration_t queue_time;

    // The total amount of time this task and its children spent handling page faults.
    // * Threads include only their own page fault handling time.
    // * Processes include the page fault time for all of their threads (including threads that
    // previously exited).
    // * Jobs include the page fault time for all of their processes (including processes that
    // previously exited).
    zx_duration_t page_fault_time;

    // The total amount of time this task and its children spent waiting on contended kernel locks.
    // * Threads include only their own wait time.
    // * Processes include the wait time for all of their threads (including threads that
    // previously exited).
    // * Jobs include the wait time for all of their processes (including processes that
    // previously exited).
    zx_duration_t lock_contention_time;
} zx_info_task_runtime_t;

The run time of a task does not include the time spent suspended or blocked waiting on events or I/O. These stats may be used to:

  1. Estimate how much CPU time a task has used.
  2. Estimate how much latency a task is experiencing due to other tasks (queue time), page fault handlers, and kernel lock contention.

ZX_INFO_PROCESS_MAPS

handle type: Process, with ZX_RIGHT_READ

buffer type: zx_info_maps_t[n]

The zx_info_maps_t array is a depth-first pre-order walk of the target process's Aspace/VMAR/Mapping tree. As per the pre-order traversal base addresses will be in ascending order.

typedef struct zx_info_maps {
    // Name if available; empty string otherwise.
    char name[ZX_MAX_NAME_LEN];
    // Base address.
    zx_vaddr_t base;
    // Size in bytes.
    size_t size;

    // The depth of this node in the tree.
    // Can be used for indentation, or to rebuild the tree from an array
    // of zx_info_maps_t entries, which will be in depth-first pre-order.
    size_t depth;
    // The type of this entry; indicates which union entry is valid.
    uint32_t type; // zx_info_maps_type_t
    union {
        zx_info_maps_mapping_t mapping;
        // No additional fields for other types.
    } u;
} zx_info_maps_t;

typedef struct zx_info_maps_mapping {
    // MMU flags for the mapping.
    // Bitwise OR of ZX_VM_PERM_{READ,WRITE,EXECUTE} values.
    zx_vm_option_t mmu_flags;
    uint8_t padding1[4];
    // koid of the mapped VMO or IOB region.
    zx_koid_t vmo_koid;
    // Offset into the above VMO or IOB region.
    uint64_t vmo_offset;
    // The number of PAGE_SIZE pages in the mapped region of the VMO or
    // IOB region that are backed by physical memory.
    size_t committed_pages;
} zx_info_maps_mapping_t;

The depth field of each entry describes its relationship to the nodes that come before it. Depth 0 is the root Aspace, depth 1 is the root VMAR, and all other entries have depth 2 or greater.

To get a full picture of how a process uses its VMOs and how a VMO is used by various processes, you may need to combine this information with ZX_INFO_PROCESS_VMOS.

See the vmaps command-line tool for an example user of this topic, and to dump the maps of arbitrary processes by koid.

Additional errors:

  • ZX_ERR_ACCESS_DENIED: If the appropriate rights are missing.
  • ZX_ERR_BAD_STATE: If the target process has terminated, or if its address space has been destroyed

ZX_INFO_PROCESS_VMOS

handle type: Process, with ZX_RIGHT_READ

buffer type: zx_info_vmo_t[n]

The zx_info_vmo_t array is list of all VMOs pointed to by the target process. Some VMOs are mapped, some are pointed to by VMO or IOB handles, and some are a combination of these. The flags field of the returned struct will indicate one of ZX_INFO_VMO_VIA_HANDLE, ZX_INFO_VMO_VIA_IOB_HANDLE, or ZX_INFO_VMO_VIA_MAPPING to allow differentiation.

Note: The same VMO may appear multiple times due to multiple mappings or handles, or because a handle to the VMO has been removed and then readded concurrently with this call. VMOs can change as the target process runs, which may result in the same VMO having different values each time it appears. The caller must resolve any duplicate values.

To get a full picture of how a process uses its VMOs and how a VMO is used by various processes, you may need to combine this information with ZX_INFO_PROCESS_MAPS.

// Describes a VMO.
typedef struct zx_info_vmo {
    // The koid of this VMO.
    zx_koid_t koid;

    // The name of this VMO.
    char name[ZX_MAX_NAME_LEN];

    // The size of this VMO; i.e., the amount of virtual address space it
    // would consume if mapped.
    uint64_t size_bytes;

    // If this VMO is a child , the koid of its parent. Otherwise, zero.
    // See |flags| for the type of child.
    zx_koid_t parent_koid;

    // The number of child of this VMO, if any.
    size_t num_children;

    // The number of times this VMO is currently mapped into VMARs.
    // Note that the same process will often map the same VMO twice,
    // and both mappings will be counted here. (I.e., this is not a count
    // of the number of processes that map this VMO; see share_count.)
    size_t num_mappings;

    // An estimate of the number of unique address spaces that
    // this VMO is mapped into. Every process has its own address space,
    // and so does the kernel.
    size_t share_count;

    // Bitwise OR of ZX_INFO_VMO_* values.
    uint32_t flags;

    // If |ZX_INFO_VMO_TYPE(flags) == ZX_INFO_VMO_TYPE_PAGED|, the amount of
    // memory currently allocated to this VMO; i.e., the amount of physical
    // memory it consumes. Undefined otherwise.
    uint64_t committed_bytes;

    // If |flags & ZX_INFO_VMO_VIA_HANDLE|, the handle rights.
    //
    // If |flags & ZX_INFO_VMO_VIA_IOB_HANDLE|, the effective combined
    // handle rights for the region and containing IOB
    //
    // Undefined otherwise.
    zx_rights_t handle_rights;

    // VMO mapping cache policy. One of ZX_CACHE_POLICY_*
    uint32_t cache_policy;

    // Amount of kernel memory, in bytes, allocated to track metadata
    // associated with this VMO.
    uint64_t metadata_bytes;

    // Running counter of the number of times the kernel, without user request,
    // performed actions on this VMO that would have caused |committed_bytes| to
    // report a different value.
    uint64_t committed_change_events;
} zx_info_vmo_t;

See the vmos command-line tool for an example user of this topic, and to dump the VMOs of arbitrary processes by koid.

ZX_INFO_KMEM_STATS

handle type: Resource (Specifically, the info resource)

buffer type: zx_info_kmem_stats_t[1]

Returns information about kernel memory usage.

typedef struct zx_info_kmem_stats {
    // The total amount of physical memory available to the system.
    // Note, the values below may not exactly add up to this total.
    size_t total_bytes;

    // The amount of unallocated memory.
    size_t free_bytes;

    // The amount of memory reserved by and mapped into the kernel for reasons
    // not covered by other fields in this struct. Typically for readonly data
    // like the ram disk and kernel image, and for early-boot dynamic memory.
    size_t wired_bytes;

    // The amount of memory allocated to the kernel heap.
    size_t total_heap_bytes;

    // The portion of |total_heap_bytes| that is not in use.
    size_t free_heap_bytes;

    // The amount of memory committed to VMOs, both kernel and user.
    // A superset of all userspace memory.
    // Does not include certain VMOs that fall under |wired_bytes|.
    size_t vmo_bytes;

    // The amount of memory used for architecture-specific MMU metadata
    // like page tables.
    size_t mmu_overhead_bytes;

    // Non-free memory that isn't accounted for in any other field.
    size_t other_bytes;
} zx_info_kmem_stats_t;

ZX_INFO_KMEM_STATS_EXTENDED

handle type: Resource (Specifically, the info resource)

buffer type: zx_info_kmem_stats_extended_t[1]

Returns information about kernel memory usage - includes information returned by the ZX_INFO_KMEM_STATS topic, plus some additional information that is more expensive to collect.

typedef struct zx_info_kmem_stats_extended {
    // The total amount of physical memory available to the system.
    uint64_t total_bytes;

    // The amount of unallocated memory.
    uint64_t free_bytes;

    // The amount of memory reserved by and mapped into the kernel for reasons
    // not covered by other fields in this struct. Typically for readonly data
    // like the ram disk and kernel image, and for early-boot dynamic memory.
    uint64_t wired_bytes;

    // The amount of memory allocated to the kernel heap.
    uint64_t total_heap_bytes;

    // The portion of |total_heap_bytes| that is not in use.
    uint64_t free_heap_bytes;

    // The amount of memory committed to VMOs, both kernel and user.
    // A superset of all userspace memory.
    // Does not include certain VMOs that fall under |wired_bytes|.
    uint64_t vmo_bytes;

    // The amount of memory committed to pager-backed VMOs.
    uint64_t vmo_pager_total_bytes;

    // The amount of memory committed to pager-backed VMOs, that has been most
    // recently accessed, and would not be eligible for eviction by the kernel
    // under memory pressure.
    uint64_t vmo_pager_newest_bytes;

    // The amount of memory committed to pager-backed VMOs, that has been least
    // recently accessed, and would be the first to be evicted by the kernel
    // under memory pressure.
    uint64_t vmo_pager_oldest_bytes;

    // The amount of memory committed to discardable VMOs that is currently
    // locked, or unreclaimable by the kernel under memory pressure.
    uint64_t vmo_discardable_locked_bytes;

    // The amount of memory committed to discardable VMOs that is currently
    // unlocked, or reclaimable by the kernel under memory pressure.
    uint64_t vmo_discardable_unlocked_bytes;

    // The amount of memory used for architecture-specific MMU metadata
    // like page tables.
    uint64_t mmu_overhead_bytes;

    // The amount of memory in use by IPC.
    uint64_t ipc_bytes;

    // Non-free memory that isn't accounted for in any other field.
    uint64_t other_bytes;

    // The amount of memory in VMOs that would otherwise be tracked for
    // reclamation, but has had reclamation disabled.
    uint64_t vmo_reclaim_disabled_bytes;
} zx_info_kmem_stats_extended_t;

ZX_INFO_KMEM_STATS_COMPRESSION

handle type: Resource (Specifically, the info resource)

buffer type: zx_info_kmem_stats_compression_t[1]

Returns information about kernel memory usage as it pertains to the compressed memory subsystem.

typedef struct zx_info_kmem_stats_compression {
    // Size in bytes of the content that is currently being compressed and stored.
    uint64_t uncompressed_storage_bytes;

    // Size in bytes of all memory, including metadata, fragmentation and other
    // overheads, of the compressed memory area. Note that due to base book
    // keeping overhead this could be non-zero, even when
    // |uncompressed_content_bytes| is zero.
    uint64_t compressed_storage_bytes;

    // Size in bytes of any fragmentation in the compressed memory area.
    uint64_t compressed_fragmentation_bytes;

    // Total amount of CPU time spent on compression across all threads.
    // Compression may happen in parallel and so this can be larger than
    // wall clock time.
    zx_duration_t compression_time;

    // Total amount of time decompression has spent on a CPU across all threads.
    // Decompression may happen in parallel and so this can increase faster than
    // wall clock time.
    zx_duration_t decompression_time;

    // Total number of times compression has been done on a page, regardless of
    // whether the compressed result was ultimately retained.
    uint64_t total_page_compression_attempts;

    // How many of the total compression attempts were considered failed and
    // were not stored. An example reason for failure would be a page not being
    // compressed sufficiently to be considered worth storing.
    uint64_t failed_page_compression_attempts;

    // Number of times pages have been decompressed.
    uint64_t total_page_decompressions;

    // Number of times a page was removed from storage without needing to be
    // decompressed. An example that would cause this is a VMO being destroyed.
    uint64_t compressed_page_evictions;

    // How many pages compressed due to the page being inactive, but without
    // there being memory pressure.
    uint64_t eager_page_compressions;

    // How many pages compressed due to general memory pressure. This excludes pages
    // compressed due to critical memory pressure.
    uint64_t memory_pressure_page_compressions;

    // How many pages compressed due to attempting to avoid OOM or near OOM
    // scenarios.
    uint64_t critical_memory_page_compressions;

    // The nanoseconds in the base unit of time for
    // |pages_decompressed_within_log_time|.
    uint64_t pages_decompressed_unit_ns;

    // How long pages spent compressed before being decompressed, grouped in log
    // buckets. Pages that got evicted, and hence were not decompressed, are not
    // counted here. Buckets are in |pages_decompressed_unit_ns| and round up
    // such that:
    // 0: Pages decompressed in <1 unit
    // 1: Pages decompressed between 1 and 2 units
    // 2: Pages decompressed between 2 and 4 units
    // ...
    // 7: Pages decompressed between 64 and 128 units
    // How many pages are held compressed for longer than 128 units can be
    // inferred by subtracting from |total_page_decompressions|.
    uint64_t pages_decompressed_within_log_time[8];
} zx_info_kmem_stats_compression_t;

ZX_INFO_RESOURCE

handle type: Resource

buffer type: zx_info_resource_t[1]

Returns information about a resource object via its handle.

typedef struct zx_info_resource {
    // The resource kind; resource object kinds are described in resource.md
    uint32_t kind;
    // Resource's creation flags
    uint32_t flags;
    // Resource's base value (inclusive)
    uint64_t base;
    // Resource's length value
    size_t size;
    char name[ZX_MAX_NAME_LEN];
} zx_info_resource_t;

The resource kind is one of

  • ZX_RSRC_KIND_ROOT
  • ZX_RSRC_KIND_MMIO
  • ZX_RSRC_KIND_IOPORT
  • ZX_RSRC_KIND_IRQ
  • ZX_RSRC_KIND_SMC
  • ZX_RSRC_KIND_SYSTEM

ZX_INFO_BTI

handle type: Bus Transaction Initiator

buffer type: zx_info_bti_t[1]

typedef struct zx_info_bti {
    // zx_bti_pin will always be able to return addresses that are contiguous for at
    // least this many bytes. E.g. if this returns 1MB, then a call to
    // zx_bti_pin() with a size of 2MB will return at most two physically-contiguous runs.
    // If the size were 2.5MB, it will return at most three physically-contiguous runs.
    uint64_t minimum_contiguity;

    // The number of bytes in the device's address space (UINT64_MAX if 2^64).
    uint64_t aspace_size;

    // The count of the pinned memory object tokens. Requesting this count is
    // racy, so this should only be used for informative reasons.
    uint64_t pmo_count;

    // The count of the quarantined pinned memory object tokens. Requesting this count is
    // racy, so this should only be used for informative reasons.
    uint64_t quarantine_count;
} zx_info_bti_t;

ZX_INFO_MEMORY_ATTRIBUTION

handle type: Job, or Process

buffer type: zx_info_memory_attribution_t[n]

Returns the memory attribution information of all processes contained in the sub-hierarchy rooted at the provided handle.

typedef struct zx_info_memory_attribution {
   // The koid of the process for which these attribution statistics apply.
   zx_koid_t process_koid;

   uint64_t private_resident_pages_allocated;
   uint64_t private_resident_pages_deallocated;

   uint64_t total_resident_pages_allocated;
   uint64_t total_resident_pages_deallocated;
} zx_info_memory_attribution_t;

Topic ZX_INFO_IOB

handle type: IOBuffer

buffer type: zx_info_iob_t[1]

Returns information about the overall IOB instance.

typedef struct zx_info_iob {
  // The value of the *options* parameter passed to `zx_iob_create`.
  uint64_t options;
  // The number of regions in the IOB.
  uint32_t region_count;
  // Reserved for future extensions.
  uint8_t padding[4];
} zx_info_iob_t;

Topic ZX_INFO_IOB_REGIONS

Returns information about each region of an IOB as an array of zx_iob_region_info_t

handle type: IOBuffer

buffer type: zx_iob_region_info_t[n]

struct zx_iob_region_info_t { // The region description, with potentially swapped access bits. zx_iob_region_t region; /// The koid of the underlying memory object. zx_koid_t koid; };

Access modifier bits are swapped, such that the Ep0 access bits reflect the access of the endpoint making the query and the Ep1 bits reflect the access of the other endpoint, making it possible to determine the access of the local and remote handles without knowing which handles were Ep0 and Ep1 when created.

Rights

If topic is ZX_INFO_PROCESS, handle must be of type ZX_OBJ_TYPE_PROCESS and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_JOB, handle must be of type ZX_OBJ_TYPE_JOB and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_PROCESS_THREADS, handle must be of type ZX_OBJ_TYPE_PROCESS and have ZX_RIGHT_ENUMERATE.

If topic is ZX_INFO_JOB_CHILDREN, handle must be of type ZX_OBJ_TYPE_JOB and have ZX_RIGHT_ENUMERATE.

If topic is ZX_INFO_JOB_PROCESSES, handle must be of type ZX_OBJ_TYPE_JOB and have ZX_RIGHT_ENUMERATE.

If topic is ZX_INFO_THREAD, handle must be of type ZX_OBJ_TYPE_THREAD and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_THREAD_EXCEPTION_REPORT, handle must be of type ZX_OBJ_TYPE_THREAD and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_THREAD_STATS, handle must be of type ZX_OBJ_TYPE_THREAD and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_TASK_STATS, handle must be of type ZX_OBJ_TYPE_PROCESS and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_PROCESS_MAPS, handle must be of type ZX_OBJ_TYPE_PROCESS and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_PROCESS_VMOS, handle must be of type ZX_OBJ_TYPE_PROCESS and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_VMO, handle must be of type ZX_OBJ_TYPE_VMO.

If topic is ZX_INFO_VMAR, handle must be of type ZX_OBJ_TYPE_VMAR and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_GUEST_STATS, handle must have resource kind ZX_RSRC_KIND_SYSTEM with base ZX_RSRC_SYSTEM_INFO_BASE.

If topic is ZX_INFO_CPU_STATS, handle must have resource kind ZX_RSRC_KIND_SYSTEM with base ZX_RSRC_SYSTEM_INFO_BASE.

If topic is ZX_INFO_KMEM_STATS, handle must have resource kind ZX_RSRC_KIND_SYSTEM with base ZX_RSRC_SYSTEM_INFO_BASE.

If topic is ZX_INFO_KMEM_STATS_EXTENDED, handle must have resource kind ZX_RSRC_KIND_SYSTEM with base ZX_RSRC_SYSTEM_INFO_BASE.

If topic is ZX_INFO_RESOURCE, handle must be of type ZX_OBJ_TYPE_RESOURCE and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_HANDLE_COUNT, handle must have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_BTI, handle must be of type ZX_OBJ_TYPE_BTI and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_PROCESS_HANDLE_STATS, handle must be of type ZX_OBJ_TYPE_PROCESS and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_SOCKET, handle must be of type ZX_OBJ_TYPE_SOCKET and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_MSI, handle must be of type ZX_OBJ_TYPE_MSI and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_TASK_RUNTIME, handle must be of type ZX_OBJ_TYPE_THREAD, ZX_OBJ_TYPE_PROCESS, or ZX_OBJ_TYPE_JOB, and have ZX_RIGHT_INSPECT.

If topic is ZX_INFO_MEMORY_ATTRIBUTION, handle must have ZX_RIGHT_INSPECT.

Return value

zx_object_get_info() returns ZX_OK on success. In the event of failure, a negative error value is returned.

Errors

ZX_ERR_BAD_HANDLE handle is not a valid handle.

ZX_ERR_WRONG_TYPE handle is not an appropriate type for topic

ZX_ERR_ACCESS_DENIED: If handle does not have the necessary rights for the operation.

ZX_ERR_INVALID_ARGS buffer, actual, or avail are invalid pointers.

ZX_ERR_NO_MEMORY Failure due to lack of memory. There is no good way for userspace to handle this (unlikely) error. In a future build this error will no longer occur.

ZX_ERR_BUFFER_TOO_SMALL The topic returns a fixed number of records, but the provided buffer is not large enough for these records.

ZX_ERR_NOT_SUPPORTED topic does not exist.

EXAMPLES

bool is_handle_valid(zx_handle_t handle) {
    return zx_object_get_info(
        handle, ZX_INFO_HANDLE_VALID, NULL, 0, NULL, NULL) == ZX_OK;
}

zx_koid_t get_object_koid(zx_handle_t handle) {
    zx_info_handle_basic_t info;
    if (zx_object_get_info(handle, ZX_INFO_HANDLE_BASIC,
                           &info, sizeof(info), NULL, NULL) != ZX_OK) {
        return 0;
    }
    return info.koid;
}

void examine_threads(zx_handle_t proc) {
    zx_koid_t threads[128];
    size_t count, avail;

    if (zx_object_get_info(proc, ZX_INFO_PROCESS_THREADS, threads,
                           sizeof(threads), &count, &avail) != ZX_OK) {
        // Error!
    } else {
        if (avail > count) {
            // More threads than space in array;
            // could call again with larger array.
        }
        for (size_t n = 0; n < count; n++) {
            do_something(thread[n]);
        }
    }
}

See also