subyte Kernel Service
Purpose
Stores a byte of data in user memory.
Syntax
Parameters
| Item | Description |
|---|---|
| uaddr | Specifies the address of user data. |
| c | Specifies the character to store. |
Description
The subyte kernel service stores a byte of data at the specified address in user memory. It is provided so that system calls and device heads can safely access user data. The subyte service ensures that the user has the appropriate authority to:
- Access the data.
- Protect the operating system from paging I/O errors on user data.
The subyte service should only be called while executing in kernel mode in the user process.
Execution Environment
The subyte kernel service can be called from the process environment only.
Return Values
| Item | Description |
|---|---|
| 0 | Indicates successful completion. |
| -1 | Indicates a uaddr parameter that is not valid for
one of the following reasons:
|