From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Piggin Date: Mon, 18 Oct 2021 09:16:25 +0000 Subject: Re: [PATCH v3 07/12] asm-generic: Define 'func_desc_t' to commonly describe function descriptors Message-Id: <1634546857.xamu59z8sr.astroid@bobo.none> List-Id: References: <1634538449.eah9b31bbz.astroid@bobo.none> <802b3ff9-8ada-b45b-2b69-b6a23f0c3664@csgroup.eu> In-Reply-To: <802b3ff9-8ada-b45b-2b69-b6a23f0c3664@csgroup.eu> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Andrew Morton , Arnd Bergmann , Benjamin Herrenschmidt , Christophe Leroy , Helge Deller , Greg Kroah-Hartman , "James E.J. Bottomley" , Kees Cook , Michael Ellerman , Paul Mackerras Cc: linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Excerpts from Christophe Leroy's message of October 18, 2021 5:07 pm: > > > Le 18/10/2021 à 08:29, Nicholas Piggin a écrit : >> Excerpts from Christophe Leroy's message of October 17, 2021 10:38 pm: >>> We have three architectures using function descriptors, each with its >>> own type and name. >>> >>> Add a common typedef that can be used in generic code. >>> >>> Also add a stub typedef for architecture without function descriptors, >>> to avoid a forest of #ifdefs. >>> >>> It replaces the similar 'func_desc_t' previously defined in >>> arch/powerpc/kernel/module_64.c >>> >>> Reviewed-by: Kees Cook >>> Acked-by: Arnd Bergmann >>> Signed-off-by: Christophe Leroy >>> --- >> >> [...] >> >>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h >>> index a918388d9bf6..33b51efe3a24 100644 >>> --- a/include/asm-generic/sections.h >>> +++ b/include/asm-generic/sections.h >>> @@ -63,6 +63,9 @@ extern __visible const void __nosave_begin, __nosave_end; >>> #else >>> #define dereference_function_descriptor(p) ((void *)(p)) >>> #define dereference_kernel_function_descriptor(p) ((void *)(p)) >>> +typedef struct { >>> + unsigned long addr; >>> +} func_desc_t; >>> #endif >>> >> >> I think that deserves a comment. If it's just to allow ifdef to be >> avoided, I guess that's okay with a comment. Would be nice if you could >> cause it to generate a link time error if it was ever used like >> undefined functions, but I guess you can't. It's not a necessity though. >> > > I tried to explain it in the commit message, but I can add a comment > here in addition for sure. Thanks. > > By the way, it IS used in powerpc's module_64.c: Ah yes of course. I guess the point is function descriptors don't exist so it should not be used (in general). powerpc module code knows what it is doing, I guess it's okay for it to use it. Thanks, Nick