arch/arm64/kernel/stacktrace.c:178:26: warning: Either the condition 'regs' is redundant or there is possible null pointer dereference: regs.

arch/arm64/kernel/stacktrace.c:178:26: warning: Either the condition 'regs' is redundant or there is possible null pointer dereference: regs.

[kernel test robot]

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CC: kbuild-all(a)lists.01.org
CC: linux-kernel(a)vger.kernel.org
TO: Mark Brown <broonie@kernel.org>
CC: Will Deacon <will@kernel.org>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   f40ddce88593482919761f74910f42f4b84c004b
commit: 9e0f085c2b33ebe13bcec53cbacce505fe78fde7 arm64: Move console stack display code to stacktrace.c
date:   5 months ago
:::::: branch date: 4 days ago
:::::: commit date: 5 months ago
compiler: aarch64-linux-gcc (GCC) 9.3.0

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


cppcheck possible warnings: (new ones prefixed by >>, may not real problems)

>> arch/arm64/kernel/stacktrace.c:178:26: warning: Either the condition 'regs' is redundant or there is possible null pointer dereference: regs. [nullPointerRedundantCheck]
     } else if (frame.fp == regs->regs[29]) {
                            ^
   arch/arm64/kernel/stacktrace.c:148:6: note: Assuming that condition 'regs' is not redundant
    if (regs) {
        ^
   arch/arm64/kernel/stacktrace.c:178:26: note: Null pointer dereference
     } else if (frame.fp == regs->regs[29]) {
                            ^

vim +/regs +178 arch/arm64/kernel/stacktrace.c

9e0f085c2b33eb Mark Brown 2020-09-21  139  
9e0f085c2b33eb Mark Brown 2020-09-21  140  void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
9e0f085c2b33eb Mark Brown 2020-09-21  141  		    const char *loglvl)
9e0f085c2b33eb Mark Brown 2020-09-21  142  {
9e0f085c2b33eb Mark Brown 2020-09-21  143  	struct stackframe frame;
9e0f085c2b33eb Mark Brown 2020-09-21  144  	int skip = 0;
9e0f085c2b33eb Mark Brown 2020-09-21  145  
9e0f085c2b33eb Mark Brown 2020-09-21  146  	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
9e0f085c2b33eb Mark Brown 2020-09-21  147  
9e0f085c2b33eb Mark Brown 2020-09-21  148  	if (regs) {
9e0f085c2b33eb Mark Brown 2020-09-21  149  		if (user_mode(regs))
9e0f085c2b33eb Mark Brown 2020-09-21  150  			return;
9e0f085c2b33eb Mark Brown 2020-09-21  151  		skip = 1;
9e0f085c2b33eb Mark Brown 2020-09-21  152  	}
9e0f085c2b33eb Mark Brown 2020-09-21  153  
9e0f085c2b33eb Mark Brown 2020-09-21  154  	if (!tsk)
9e0f085c2b33eb Mark Brown 2020-09-21  155  		tsk = current;
9e0f085c2b33eb Mark Brown 2020-09-21  156  
9e0f085c2b33eb Mark Brown 2020-09-21  157  	if (!try_get_task_stack(tsk))
9e0f085c2b33eb Mark Brown 2020-09-21  158  		return;
9e0f085c2b33eb Mark Brown 2020-09-21  159  
9e0f085c2b33eb Mark Brown 2020-09-21  160  	if (tsk == current) {
9e0f085c2b33eb Mark Brown 2020-09-21  161  		start_backtrace(&frame,
9e0f085c2b33eb Mark Brown 2020-09-21  162  				(unsigned long)__builtin_frame_address(0),
9e0f085c2b33eb Mark Brown 2020-09-21  163  				(unsigned long)dump_backtrace);
9e0f085c2b33eb Mark Brown 2020-09-21  164  	} else {
9e0f085c2b33eb Mark Brown 2020-09-21  165  		/*
9e0f085c2b33eb Mark Brown 2020-09-21  166  		 * task blocked in __switch_to
9e0f085c2b33eb Mark Brown 2020-09-21  167  		 */
9e0f085c2b33eb Mark Brown 2020-09-21  168  		start_backtrace(&frame,
9e0f085c2b33eb Mark Brown 2020-09-21  169  				thread_saved_fp(tsk),
9e0f085c2b33eb Mark Brown 2020-09-21  170  				thread_saved_pc(tsk));
9e0f085c2b33eb Mark Brown 2020-09-21  171  	}
9e0f085c2b33eb Mark Brown 2020-09-21  172  
9e0f085c2b33eb Mark Brown 2020-09-21  173  	printk("%sCall trace:\n", loglvl);
9e0f085c2b33eb Mark Brown 2020-09-21  174  	do {
9e0f085c2b33eb Mark Brown 2020-09-21  175  		/* skip until specified stack frame */
9e0f085c2b33eb Mark Brown 2020-09-21  176  		if (!skip) {
9e0f085c2b33eb Mark Brown 2020-09-21  177  			dump_backtrace_entry(frame.pc, loglvl);
9e0f085c2b33eb Mark Brown 2020-09-21 @178  		} else if (frame.fp == regs->regs[29]) {
9e0f085c2b33eb Mark Brown 2020-09-21  179  			skip = 0;
9e0f085c2b33eb Mark Brown 2020-09-21  180  			/*
9e0f085c2b33eb Mark Brown 2020-09-21  181  			 * Mostly, this is the case where this function is
9e0f085c2b33eb Mark Brown 2020-09-21  182  			 * called in panic/abort. As exception handler's
9e0f085c2b33eb Mark Brown 2020-09-21  183  			 * stack frame does not contain the corresponding pc
9e0f085c2b33eb Mark Brown 2020-09-21  184  			 * at which an exception has taken place, use regs->pc
9e0f085c2b33eb Mark Brown 2020-09-21  185  			 * instead.
9e0f085c2b33eb Mark Brown 2020-09-21  186  			 */
9e0f085c2b33eb Mark Brown 2020-09-21  187  			dump_backtrace_entry(regs->pc, loglvl);
9e0f085c2b33eb Mark Brown 2020-09-21  188  		}
9e0f085c2b33eb Mark Brown 2020-09-21  189  	} while (!unwind_frame(tsk, &frame));
9e0f085c2b33eb Mark Brown 2020-09-21  190  
9e0f085c2b33eb Mark Brown 2020-09-21  191  	put_task_stack(tsk);
9e0f085c2b33eb Mark Brown 2020-09-21  192  }
9e0f085c2b33eb Mark Brown 2020-09-21  193  

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