RE: [PATCH 02/11] x86: tboot: avoid Wstringop-overread-warning

[David Laight <David.Laight@ACULAB.COM>]

From: David Laight
> Sent: 24 March 2021 09:12
> 
> From: Martin Sebor
> > Sent: 22 March 2021 22:08
> ...
> > In GCC 11, all access warnings expect objects to be either declared
> > or allocated.  Pointers with constant values are taken to point to
> > nothing valid (as Arnd mentioned above, this is to detect invalid
> > accesses to members of structs at address zero).
> >
> > One possible solution to the known address problem is to extend GCC
> > attributes address and io that pin an object to a hardwired address
> > to all targets (at the moment they're supported on just one or two
> > targets).  I'm not sure this can still happen before GCC 11 releases
> > sometime in April or May.
> 
> A different solution is to define a normal C external data item
> and then assign a fixed address with an asm statement or in
> the linker script.

Or stop gcc tracking the value by using:
	struct foo *foo = (void *)xxxxx;
	asm ("", "+r" (foo));

If the address is used more than once forcing it into
a register is also likely to generate better code.

	David

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