Comment 3 for bug 1449610

The specification says that SVC is supported in all versions of the Thumb
instruction set in the section I referenced earlier.

Furthermore, if you had thoroughly read the section you referenced, you
would have seen the note:

[quote]
In an ARMv6-M implementation that does not include the
Unprivileged/Privileged Extension,
execution is always privileged.

[emphasis added] However in such an implementation, application code might
use
supervisor calls to maintain a software hierarchy with a system
kernel.[/emphasis added]
[/quote]

Shall I file the bug upstream as well?

Thank you.

C

On Apr 30, 2015 3:05 AM, "Tony Liu" <email address hidden> wrote:
> The unprivileged/privileged extension is optional for armv6-m
> architecture implementation.[1] Without this extension, it will not
> support Supervisor Call (SVC). If you want to use SVC, you need to
> specify the target of -march=armv6s-m.
>
> It will also be better to use -mcpu=cortex-m0 rather than
> -march=armv6-m, because CPUs like Cortex-m0, Coetex-m0+ are implemented
> with the unprivileged/privileged extension.
>
> BR,
> Tony
>
> [1]You can find more information about such extension in the section
> A1.2 and A4.9 in the ARMv6m Architecture Reference Manual.
>
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> report.
> https://bugs.launchpad.net/bugs/1449610
>
> Title:
> SVC is not permitted on this architecture
>
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