% PT_IMAGE_SET_CALLBACK(3)

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# NAME

pt_image_set_callback - set a traced memory image read memory callback


# SYNOPSIS

| **\#include `<intel-pt.h>`**
|
| **typedef int (read_memory_callback_t)(uint8_t \**buffer*, size_t *size*,**
|				                       **const struct pt_asid \**asid*,**
|				                       **uint64_t *ip*, void \**context*);**
|
| **int pt_image_set_callback(struct pt_image \**image*,**
|					        **read_memory_callback_t \**callback*,**
|                           **void \**context*);**

Link with *-lipt*.


# DESCRIPTION

**pt_image_set_callback**() sets the function pointed to by *callback* as the
read-memory callback function in the *pt_image* object pointed to by *image*.
Any previous read-memory callback function is replaced.  The read-memory
callback function can be removed by passing NULL as *callback* argument.

When the Intel(R) Processor Trace (Intel PT) instruction flow decoder that is
using *image* tries to read memory from a location that is not contained in any
of the file sections in *image*, it calls the read-memory callback function with
the following arguments:

buffer
:   A pre-allocated memory buffer to hold the to-be-read memory.  The callback
    function shall provide the read memory in that buffer.

size
:   The size of the memory buffer pointed to by the *buffer* argument.

asid
:   The address-space identifier specifying the process, guest, or hypervisor,
    in which context the *ip* argument is to be interpreted.  See
    **pt_image_add_file**(3).

ip
:   The virtual address from which *size* bytes of memory shall be read.

context
:   The *context* argument passed to **pt_image_set_callback**().

The callback function shall return the number of bytes read on success (no more
than *size*) or a negative *pt_error_code* enumeration constant in case of an
error.


# RETURN VALUE

**pt_image_set_callback**() returns zero on success or a negative
*pt_error_code* enumeration constant in case of an error.


# ERRORS

pte_invalid
:   If the *image* argument is NULL.


# SEE ALSO

**pt_image_alloc**(3), **pt_image_free**(3), **pt_image_add_file**(3),
**pt_image_copy**(3), **pt_image_remove_by_filename**(3),
**pt_image_remove_by_asid**(3), **pt_insn_set_image**(3),
**pt_insn_get_image**(3)
