[PATCH] arm: make it one-personality arch

Dmitry V. Levin ldv at altlinux.org
Wed Feb 20 23:16:21 UTC 2013

On Wed, Feb 20, 2013 at 07:08:13PM +0100, Denys Vlasenko wrote:
> ARM in fact _is_ one personality.
> We have two personalities for it because it has a handful of
> syscalls with huge scnos (0x000f00xx).
> Extending syscall table to have [0x000f0005] index is of course
> not a good idea.
> Someone decided to handle that by having a separate personality
> just for these syscalls.
> But multi-personality arch does a bit more work in other parts:
> This patch is another alternative: "move" 0x000f00nn syscalls
> down to the entries just above last ordinary syscall,
> by manipulating scno if it falls into the 0x000f00xx range.
> Yet another alternative is to simply treat all 0x000f00nn syscalls
> as "undefined" - print them as "syscall_nnn" as we do now
> for undefined syscalls.
> This alternative can be realized by removing from this patch
> the code block below "//TODO: why bother?" comment.
> This would be almost as good as what we have now:
> all these "special syscalls" are printargs anyway.
> The _ONLY_ thing we do for them now is we supply
> somewhat meaningful names for them.
> Please review and let me know what you think.

I'm not quite comfortable with remapping "odd" syscall numbers from
interval to
(0x000f0000; 0x000f0000 + ARM_LAST_SPECIAL_SYSCALL] interval
because they would be displayed as "syscall_nnn" with "nnn" different
from their real values.

Besides that, the change looks OK.

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