linux-kernel - Re: [PATCH][next] ftrace: Fix -Wcast-function-type warnings on powerpc64

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Message-ID: <20211005165027.GA797862@embeddedor>
Date:   Tue, 5 Oct 2021 11:50:27 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] ftrace: Fix -Wcast-function-type warnings on
 powerpc64

On Tue, Oct 05, 2021 at 12:35:22PM -0400, Steven Rostedt wrote:
> On Tue, 5 Oct 2021 11:18:12 -0500
> "Gustavo A. R. Silva" <gustavoars@...nel.org> wrote:
> 
> > On Tue, Oct 05, 2021 at 11:17:14AM -0400, Steven Rostedt wrote:
> > > On Tue, 5 Oct 2021 00:39:22 -0500
> > > "Gustavo A. R. Silva" <gustavoars@...nel.org> wrote:
> > >   
> > > > In order to make sure new function cast mismatches are not introduced
> > > > in the kernel (to avoid tripping CFI checking), the kernel should be
> > > > globally built with -Wcast-function-type.
> > > > 
> > > > So, fix the following -Wcast-function-type warnings on powerpc64
> > > > (ppc64_defconfig):  
> > > 
> > > I think I'll go back and add my linker magic.
> > > 
> > >   https://lore.kernel.org/all/20200617165616.52241bde@oasis.local.home/
> > > 
> > > I'll clean it up a bit too. I'll have a patch in a bit.  
> > 
> > Awesome. :)
> > 
> > Thanks
> > --
> 
> Does this fix it for you?

Nop; there are still some warnings (ppc64_defconfig):

kernel/trace/ftrace.c: In function ‘ftrace_ops_get_list_func’:
kernel/trace/ftrace.c:171:10: error: returning ‘void (*)(long unsigned int,  long unsigned int,  struct ftrace_ops *, struct ftrace_regs *)’ from a function with incompatible return type ‘ftrace_func_t’ {aka ‘void (*)(long unsigned int,  long unsigned int)’} [-Werror=incompatible-pointer-types]
  171 |   return ftrace_ops_list_func;
      |          ^~~~~~~~~~~~~~~~~~~~
kernel/trace/ftrace.c: In function ‘update_ftrace_function’:
kernel/trace/ftrace.c:204:8: error: assignment to ‘ftrace_func_t’ {aka ‘void (*)(long unsigned int,  long unsigned int)’} from incompatible pointer type ‘void (*)(long unsigned int,  long unsigned int,  struct ftrace_ops *, struct ftrace_regs *)’ [-Werror=incompatible-pointer-types]
  204 |   func = ftrace_ops_list_func;
      |        ^
kernel/trace/ftrace.c:217:11: warning: comparison of distinct pointer types lacks a cast
  217 |  if (func == ftrace_ops_list_func) {
      |           ^~
kernel/trace/ftrace.c: In function ‘ftrace_modify_all_code’:
kernel/trace/ftrace.c:2695:35: error: passing argument 1 of ‘ftrace_update_ftrace_func’ from incompatible pointer type [-Werror=incompatible-pointer-types]
 2695 |   err = ftrace_update_ftrace_func(ftrace_ops_list_func);
      |                                   ^~~~~~~~~~~~~~~~~~~~
      |                                   |
      |                                   void (*)(long unsigned int,  long unsigned int,  struct ftrace_ops *, struct ftrace_regs *)
In file included from kernel/trace/ftrace.c:29:
./include/linux/ftrace.h:585:52: note: expected ‘ftrace_func_t’ {aka ‘void (*)(long unsigned int,  long unsigned int)’} but argument is of type ‘void (*)(long unsigned int,  long unsigned int,  struct ftrace_ops *, struct ftrace_regs *)’
  585 | extern int ftrace_update_ftrace_func(ftrace_func_t func);
      |                                      ~~~~~~~~~~~~~~^~~~
kernel/trace/ftrace.c:2705:38: warning: comparison of distinct pointer types lacks a cast
 2705 |  if (update && ftrace_trace_function != ftrace_ops_list_func) {
      |                                      ^~

--
Gustavo