On Fri, Apr 16, 2021 at 03:06:17PM -0700, Andy Lutomirski wrote:
> On Fri, Apr 16, 2021 at 3:03 PM Borislav Petkov <b...@alien8.de> wrote:
> >
> > On Fri, Apr 16, 2021 at 02:49:23PM -0700, Sami Tolvanen wrote:
> > > __nocfi only disables CFI checking in a function, the compiler still
> > > changes function addresses to point to the CFI jump table, which is
> > > why we need function_nocfi().
> >
> > So call it __func_addr() or get_function_addr() or so, so that at least
> > it is clear what this does.
> >
>
> This seems backwards to me. If I do:
>
> extern void foo(some signature);
>
> then I would, perhaps naively, expect foo to be the actual symbol that
I'm just reading the patch:
... The function_nocfi macro always returns the address of the
+ * actual function instead.
+ */
+#define function_nocfi(x) ({ \
+ void *addr; \
+ asm("leaq " __stringify(x) "(%%rip), %0\n\t" : "=r" (addr)); \
+ addr;
so it does a rip-relative load into a reg which ends up with the function
address.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
