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* [PATCH] ftrace/sh: Add arch_ftrace_ops_list_func stub to have compressed image still link
@ 2021-10-22  2:16 Steven Rostedt
  2021-10-27  5:21 ` kernel test robot
  0 siblings, 1 reply; 2+ messages in thread
From: Steven Rostedt @ 2021-10-22  2:16 UTC (permalink / raw)
  To: LKML; +Cc: Ingo Molnar, Andrew Morton, Yoshinori Sato, Rich Felker, linux-sh

Using the linker script to fix an issue where some archs call the
function tracer with just the ip (instruction pointer) and pip (parent
instruction pointer) where as more up to date archs also pass in the
associated ftrace_ops and the ftrace_regs pointer, the generic code
will be called either with two parameters or four. To avoid any C
undefined behavior of calling two parameters to four or four to two
parameter function, two functions are created, where a preprocessor
macro uses the one that matches the architecture. As the function
pointers for them may be different, a typecast is used. But this
triggers issues with newer compilers that will fail due to -Werror.

A linker trick is now used to map the generic function to the function
that is used (note the generic function is only used to set the default
function callback). The linker trick defines ftrace_ops_list_func (the
generic function) to arch_ftrace_ops_list_func (the arch defined one).

Link: https://lore.kernel.org/all/20200617165616.52241bde@oasis.local.home/

But this fails sh arch because their linker script is included in their
compressed image that does not define arch_ftrace_ops_list_func at all

  sh4-linux-ld:arch/sh/boot/compressed/../../kernel/vmlinux.lds:32: undefined symbol `arch_ftrace_ops_list_func' referenced in expression

Included a stub by that name in the misc.c to allow the code to
compile and link, even though it's not used.

This is similar to what was done for ftrace_stub:

  b83b43ffc6e4b ("fgraph: Fix function type mismatches of
  ftrace_graph_return using ftrace_stub")

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
This is based on my tree at:
  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
  branch: ftrace/core
  I can push this change through my tree with the SuperH maintainer's acks.

diff --git a/arch/sh/boot/compressed/misc.c b/arch/sh/boot/compressed/misc.c
index a03b6680a9d9..ca05c99a3d5b 100644
--- a/arch/sh/boot/compressed/misc.c
+++ b/arch/sh/boot/compressed/misc.c
@@ -115,6 +115,9 @@ void __stack_chk_fail(void)
 void ftrace_stub(void)
 {
 }
+void arch_ftrace_ops_list_func(void)
+{
+}
 
 #define stackalign	4
 


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] ftrace/sh: Add arch_ftrace_ops_list_func stub to have compressed image still link
  2021-10-22  2:16 [PATCH] ftrace/sh: Add arch_ftrace_ops_list_func stub to have compressed image still link Steven Rostedt
@ 2021-10-27  5:21 ` kernel test robot
  0 siblings, 0 replies; 2+ messages in thread
From: kernel test robot @ 2021-10-27  5:21 UTC (permalink / raw)
  To: Steven Rostedt, LKML
  Cc: kbuild-all, Ingo Molnar, Andrew Morton,
	Linux Memory Management List, Yoshinori Sato, Rich Felker,
	linux-sh

[-- Attachment #1: Type: text/plain, Size: 2717 bytes --]

Hi Steven,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linux/master]
[also build test WARNING on hnaz-mm/master linus/master v5.15-rc7 next-20211026]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Steven-Rostedt/ftrace-sh-Add-arch_ftrace_ops_list_func-stub-to-have-compressed-image-still-link/20211022-101651
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2f111a6fd5b5297b4e92f53798ca086f7c7d33a4
config: sh-se7705_defconfig (attached as .config)
compiler: sh4-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/67866b4041f96ae1a8bc1b0b0d077c13c59a0e24
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Steven-Rostedt/ftrace-sh-Add-arch_ftrace_ops_list_func-stub-to-have-compressed-image-still-link/20211022-101651
        git checkout 67866b4041f96ae1a8bc1b0b0d077c13c59a0e24
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=sh 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   arch/sh/boot/compressed/misc.c:109:6: warning: no previous prototype for '__stack_chk_fail' [-Wmissing-prototypes]
     109 | void __stack_chk_fail(void)
         |      ^~~~~~~~~~~~~~~~
   arch/sh/boot/compressed/misc.c:115:6: warning: no previous prototype for 'ftrace_stub' [-Wmissing-prototypes]
     115 | void ftrace_stub(void)
         |      ^~~~~~~~~~~
>> arch/sh/boot/compressed/misc.c:118:6: warning: no previous prototype for 'arch_ftrace_ops_list_func' [-Wmissing-prototypes]
     118 | void arch_ftrace_ops_list_func(void)
         |      ^~~~~~~~~~~~~~~~~~~~~~~~~
   arch/sh/boot/compressed/misc.c:128:6: warning: no previous prototype for 'decompress_kernel' [-Wmissing-prototypes]
     128 | void decompress_kernel(void)
         |      ^~~~~~~~~~~~~~~~~


vim +/arch_ftrace_ops_list_func +118 arch/sh/boot/compressed/misc.c

   113	
   114	/* Needed because vmlinux.lds.h references this */
   115	void ftrace_stub(void)
   116	{
   117	}
 > 118	void arch_ftrace_ops_list_func(void)
   119	{
   120	}
   121	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 10399 bytes --]

^ permalink raw reply	[flat|nested] 2+ messages in thread

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