Re: [kernel-hardening] Re: [PATCH 4/4] refcount: Report failures through CHECK_DATA_CORRUPTION

[Peter Zijlstra]

On Tue, Feb 07, 2017 at 04:03:01PM +0000, Mark Rutland wrote:
> For x86 it's a little painful due to '%' in the register names, but it looks
> possible. The below appears to do the mangling correctly (then screams due to
> the mangled result being nonexistent).

> asm(
> "	.macro	reg_to_offset	r\n"
> "	.irp rs,eax,ebx,ecx,edx\n"
> "	.ifc \\r, %\\rs\n"
> "	__offset_of_\\rs\n"
> "	.endif\n"
> "	.endr\n"
> "	.endm\n"
> );
> 
> #define asm_sym(var)		asm volatile("reg_to_offset %0\n" : : "r" (var))

Oh gawd that's a most gnarly hack.

Do we want to go do that for all archs or somehow cook a generic
fallback that ends up doing a full function call or something?