diff options
Diffstat (limited to 'doc/supplements/i386/callconv.texi')
| -rw-r--r-- | doc/supplements/i386/callconv.texi | 121 |
1 files changed, 0 insertions, 121 deletions
diff --git a/doc/supplements/i386/callconv.texi b/doc/supplements/i386/callconv.texi deleted file mode 100644 index 1846c810a4..0000000000 --- a/doc/supplements/i386/callconv.texi +++ /dev/null @@ -1,121 +0,0 @@ -@c -@c COPYRIGHT (c) 1988-1998. -@c On-Line Applications Research Corporation (OAR). -@c All rights reserved. -@c -@c $Id$ -@c - -@ifinfo -@node Calling Conventions, Calling Conventions Introduction, CPU Model Dependent Features Floating Point Unit, Top -@end ifinfo -@chapter Calling Conventions -@ifinfo -@menu -* Calling Conventions Introduction:: -* Calling Conventions Processor Background:: -* Calling Conventions Calling Mechanism:: -* Calling Conventions Register Usage:: -* Calling Conventions Parameter Passing:: -* Calling Conventions User-Provided Routines:: -@end menu -@end ifinfo - -@ifinfo -@node Calling Conventions Introduction, Calling Conventions Processor Background, Calling Conventions, Calling Conventions -@end ifinfo -@section Introduction - -Each high-level language compiler generates -subroutine entry and exit code based upon a set of rules known -as the compiler's calling convention. These rules address the -following issues: - -@itemize @bullet -@item register preservation and usage - -@item parameter passing - -@item call and return mechanism -@end itemize - -A compiler's calling convention is of importance when -interfacing to subroutines written in another language either -assembly or high-level. Even when the high-level language and -target processor are the same, different compilers may use -different calling conventions. As a result, calling conventions -are both processor and compiler dependent. - -@ifinfo -@node Calling Conventions Processor Background, Calling Conventions Calling Mechanism, Calling Conventions Introduction, Calling Conventions -@end ifinfo -@section Processor Background - -The i386 architecture supports a simple yet effective -call and return mechanism. A subroutine is invoked via the call -(call) instruction. This instruction pushes the return address -on the stack. The return from subroutine (ret) instruction pops -the return address off the current stack and transfers control -to that instruction. It is is important to note that the i386 -call and return mechanism does not automatically save or restore -any registers. It is the responsibility of the high-level -language compiler to define the register preservation and usage -convention. - -@ifinfo -@node Calling Conventions Calling Mechanism, Calling Conventions Register Usage, Calling Conventions Processor Background, Calling Conventions -@end ifinfo -@section Calling Mechanism - -All RTEMS directives are invoked using a call -instruction and return to the user application via the ret -instruction. - -@ifinfo -@node Calling Conventions Register Usage, Calling Conventions Parameter Passing, Calling Conventions Calling Mechanism, Calling Conventions -@end ifinfo -@section Register Usage - -As discussed above, the call instruction does not -automatically save any registers. RTEMS uses the registers EAX, -ECX, and EDX as scratch registers. These registers are not -preserved by RTEMS directives therefore, the contents of these -registers should not be assumed upon return from any RTEMS -directive. - -@ifinfo -@node Calling Conventions Parameter Passing, Calling Conventions User-Provided Routines, Calling Conventions Register Usage, Calling Conventions -@end ifinfo -@section Parameter Passing - -RTEMS assumes that arguments are placed on the -current stack before the directive is invoked via the call -instruction. The first argument is assumed to be closest to the -return address on the stack. This means that the first argument -of the C calling sequence is pushed last. The following -pseudo-code illustrates the typical sequence used to call a -RTEMS directive with three (3) arguments: - -@example -push third argument -push second argument -push first argument -invoke directive -remove arguments from the stack -@end example - -The arguments to RTEMS are typically pushed onto the -stack using a push instruction. These arguments must be removed -from the stack after control is returned to the caller. This -removal is typically accomplished by adding the size of the -argument list in bytes to the stack pointer. - -@ifinfo -@node Calling Conventions User-Provided Routines, Memory Model, Calling Conventions Parameter Passing, Calling Conventions -@end ifinfo -@section User-Provided Routines - -All user-provided routines invoked by RTEMS, such as -user extensions, device drivers, and MPCI routines, must also -adhere to these calling conventions. - |