Changes

== Syscalls (via syscall instruction) ==

== Syscalls (via syscall instruction) ==

These types of syscalls are created with the thumb syscall instruction. When the u16 from retaddr-0x2 matches 0xdfab(intended as thumb "svc 0xab" but ARM "svc 0xdfab" would pass too), it will just return from the exception-handler, otherwise it will do the same thing described [[IOSU|here]] for exceptions. These syscalls are [http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0471c/Bgbjhiea.html RealView semihosting operations] that allow communication with a debugger.<br>

These types of syscalls are created with the thumb syscall instruction. When the u16 from retaddr-0x2 matches 0xdfab(intended as thumb "svc 0xab" but ARM "svc 0xdfab" would pass too), it will just return from the exception-handler, otherwise it will do the same thing described [[IOSU|here]] for exceptions. These syscalls are [http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0471c/Bgbjhiea.html RealView semihosting operations] that allow communication with a debugger.<br>

Currently only syscall 0x04 is still used in production versions of IOSU.

Currently only syscall 0x04 is still used in production versions of IOSU. Syscall 0x06 is only used for a scanf call in some kind of debug configuration, with the following prompt: "Enter '1' to proceed with kernel startup."

<source lang="c">

<source lang="c">

| 0x05 || __sys_write || unused  ||

| 0x05 || __sys_write || unused  ||

|-

|-

| 0x06 || __sys_read || unused ||

| 0x06 || __sys_read || Reads input from debugger stdin ||

|-

|-

| 0x07 || __sys_readc || unused  ||

| 0x07 || __sys_readc || unused  ||