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@node ARM
@chapter ARM
Arm Ltd's 32-bit ARM RISC architecture.
Forked from the venerable ARMulator project.
@node ARM ISA Support
@section ISA Support
ARM6, ARM7, ARM32, and Thumb are supported.
@node ARM Environment Support
@section Environment Support
Only the virtual environment is supported.
@node ARM Virtual Environment Syscall ABI
@subsection Virtual Environment Syscall ABI
The syscall ABI, as used by @url{https://sourceware.org/redboot/,RedBoot} and
@value{libgloss} in the virtual environment, uses the interface defined in the
following table.
@c There is also support for syscall NR in the SWI number instead of R0, but
@c documenting just this one interface seems easiest.
@c The thumb "swi 0x18" does not appear to be implemented currently.
@multitable @columnfractions .2 .3 .5
@headitem Field @tab Assembly/Register @tab Description
@item instruction
@tab @center @code{swi 0x180001;}
@tab The assembly instruction to invoke the syscall handler.
@item (in) syscall NR
@tab @center @code{R0}
@tab The system call number to select which function to run.
@item (in) arg 1
@tab @center @code{R1}
@tab The first syscall argument.
@item (in) arg 2
@tab @center @code{R2}
@tab The second syscall argument.
@item (in) arg 3
@tab @center @code{R3}
@tab The third syscall argument.
@item (in) arg 4
@tab @center @code{R4}
@tab The fourth syscall argument.
@item (in) arg 5
@tab @center @code{R5}
@tab The fifth syscall argument.
@item (in) arg 6
@tab @center @code{R6}
@tab The sixth syscall argument.
@item (out) return & error
@tab @center @code{R0}
@tab The return value (most commonly used).
@end multitable
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