x86/mm: Simplify RESERVE_BRK()

x86/mm: Simplify RESERVE_BRK()

commit a1e2c031ec3949b8c039b739c0b5bf9c30007b00 upstream.

RESERVE_BRK() reserves data in the .brk_reservation section.  The data
is initialized to zero, like BSS, so the macro specifies 'nobits' to
prevent the data from taking up space in the vmlinux binary.  The only
way to get the compiler to do that (without putting the variable in .bss
proper) is to use inline asm.

The macro also has a hack which encloses the inline asm in a discarded
function, which allows the size to be passed (global inline asm doesn't
allow inputs).

Remove the need for the discarded function hack by just stringifying the
size rather than supplying it as an input to the inline asm.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220506121631.133110232@infradead.org
[nathan: Resolve conflict due to lack of 2b6ff7dea670]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>