Re: [PATCH 08/10] ARM: kprobes: Make a frame pointer on __kretprobe_trampoline

[kernel test robot]

Hi Masami,

I love your patch! Yet something to improve:

[auto build test ERROR on rostedt-trace/for-next]
[also build test ERROR on next-20211015]
[cannot apply to arm64/for-next/core tip/x86/core linus/master v5.15-rc5]
[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/Masami-Hiramatsu/kprobes-Make-KUnit-and-add-stacktrace-on-kretprobe-tests/20211015-205329
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git for-next
config: arm-randconfig-r016-20211015 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 6069a6a5049497a32a50a49661c2f4169078bdba)
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
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/0day-ci/linux/commit/4039c4f80aba40806049567ad4f916bc4b9c1576
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Masami-Hiramatsu/kprobes-Make-KUnit-and-add-stacktrace-on-kretprobe-tests/20211015-205329
        git checkout 4039c4f80aba40806049567ad4f916bc4b9c1576
        # save the attached .config to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash

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

All errors (new ones prefixed by >>):

   arch/arm/probes/kprobes/core.c:236:16: warning: no previous prototype for function 'kprobe_handler' [-Wmissing-prototypes]
   void __kprobes kprobe_handler(struct pt_regs *regs)
                  ^
   arch/arm/probes/kprobes/core.c:236:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void __kprobes kprobe_handler(struct pt_regs *regs)
   ^
   static 
>> arch/arm/probes/kprobes/core.c:379:38: error: writeback register not allowed in register list
                   "ldr    lr, =__kretprobe_trampoline     \n\t"
                                                             ^
   <inline asm>:2:13: note: instantiated into assembly here
           stmdb   sp!, {sp, lr, pc}       
                        ^
   1 warning and 1 error generated.


vim +379 arch/arm/probes/kprobes/core.c

   367	
   368	/*
   369	 * When a retprobed function returns, trampoline_handler() is called,
   370	 * calling the kretprobe's handler. We construct a struct pt_regs to
   371	 * give a view of registers r0-r11, sp, lr, and pc to the user
   372	 * return-handler. This is not a complete pt_regs structure, but that
   373	 * should be enough for stacktrace from the return handler with or
   374	 * without pt_regs.
   375	 */
   376	void __naked __kprobes __kretprobe_trampoline(void)
   377	{
   378		__asm__ __volatile__ (
 > 379			"ldr	lr, =__kretprobe_trampoline	\n\t"
   380			"stmdb	sp!, {sp, lr, pc}	\n\t"
   381	#ifdef CONFIG_FRAME_POINTER
   382		/* __kretprobe_trampoline makes a framepointer on pt_regs. */
   383	#ifdef CONFIG_CC_IS_CLANG
   384			/* In clang case, pt_regs->ip = lr. */
   385			"stmdb	sp!, {lr}		\n\t"
   386			"stmdb	sp!, {r0 - r11}		\n\t"
   387			/* fp points regs->r11 (fp) */
   388			"add	fp, sp,	#44		\n\t"
   389	#else /* !CONFIG_CC_IS_CLANG */
   390			/* In gcc case, pt_regs->ip = fp. */
   391			"stmdb	sp!, {fp}		\n\t"
   392			"stmdb	sp!, {r0 - r11}		\n\t"
   393			/* fp points regs->r15 (pc) */
   394			"add	fp, sp, #60		\n\t"
   395	#endif /* CONFIG_CC_IS_CLANG */
   396	#else /* !CONFIG_FRAME_POINTER */
   397			"sub	sp, sp, #4		\n\t"
   398			"stmdb	sp!, {r0 - r11}		\n\t"
   399	#endif /* CONFIG_FRAME_POINTER */
   400			"mov	r0, sp			\n\t"
   401			"bl	trampoline_handler	\n\t"
   402			"mov	lr, r0			\n\t"
   403			"ldmia	sp!, {r0 - r11}		\n\t"
   404			"add	sp, sp, #16		\n\t"
   405	#ifdef CONFIG_THUMB2_KERNEL
   406			"bx	lr			\n\t"
   407	#else
   408			"mov	pc, lr			\n\t"
   409	#endif
   410			: : : "memory");
   411	}
   412	

---
0-DAY CI Kernel Test Service, Intel Corporation
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