main/syscalls/process_read_memory.md

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# zx_process_read_memory

## Summary

Read from the given process's address space.

## Declaration

```c
#include <zircon/syscalls.h>

zx_status_t zx_process_read_memory(zx_handle_t handle,
                                   zx_vaddr_t vaddr,
                                   void* buffer,
                                   size_t buffer_size,
                                   size_t* actual);
```

## Description

`zx_process_read_memory()` attempts to read memory of the specified process.

This function will eventually be replaced with something VMO-centric.

*vaddr* the address of the block of memory to read.

*buffer* pointer to a user buffer to read bytes into.

*buffer_size* number of bytes to attempt to read. *buffer* buffer must be large
enough for at least this many bytes. *buffer_size* must be greater than zero
and less than or equal to 64MB.

*actual* the actual number of bytes read is stored here. Less bytes than
requested may be returned if *vaddr*+*buffer_size* extends beyond the memory
mapped in the process.

## Rights

*handle* must be of type `ZX_OBJ_TYPE_PROCESS` and have `ZX_RIGHT_READ` and have `ZX_RIGHT_WRITE`.

## Return value

`zx_process_read_memory()` returns `ZX_OK` on success.
In the event of failure, a negative error value is returned, and the number of
bytes written to *buffer* is undefined.

## Errors

`ZX_ERR_ACCESS_DENIED`  *handle* does not have the `ZX_RIGHT_READ` right
or
`ZX_WRITE_RIGHT` is needed for historical reasons.

`ZX_ERR_BAD_HANDLE`  *handle* is not a valid handle.

`ZX_ERR_BAD_STATE`  the process's memory is not accessible (e.g.,
the process is being terminated),
or the requested memory is not cacheable.

`ZX_ERR_INVALID_ARGS` *buffer* is an invalid pointer or NULL,
or *buffer_size* is zero or greater than 64MB.

`ZX_ERR_NOT_FOUND` if the process does not have any memory at the
requested address or `ZX_ERR_OUT_OF_RANGE` if the offset corresponding
to *vaddr* within the mapped VMO is greater than or equal to the VMO
size. These error codes are consistent with the error code that would be
generated by a page fault at the same address (i.e. the *synth_code* in
the page fault's exception report).

`ZX_ERR_WRONG_TYPE`  *handle* is not a process handle.

## See also

 - [`zx_process_write_memory()`]

[`zx_process_write_memory()`]: process_write_memory.md