Re: [PATCH] Revert "x86/uaccess: Add stack frame output operand in get_user() inline asm"

[Andrey Ryabinin]

2017-07-19 20:46 GMT+03:00 Josh Poimboeuf <jpoimboe@xxxxxxxxxx>:

>
> After doing some testing, I don't think this approach is going to work
> after all.  In addition to forcing the stack frame, it also causes GCC
> to add an unnecessary extra instruction to the epilogue of each affected
> function:
>
>   lea    -0x10(%rbp),%rsp
>
> We shouldn't be inserting extra instructions like that.  I also don't
> think the other suggestion of turning the '__sp' register variable into
> a global variable is a very good solution either, as that just wastes
> memory for no reason.
>

Wastes memory? How is that wastes memory? That doesn't make any sense.

> It would be nice if both compilers could agree on a way to support this.
>
> --
> Josh