Re: [PATCH] arm64: syscall: Ensure saved x0 is kept in-sync with tracer updates

[kernel test robot <lkp@intel.com>]

Hi Will,

kernel test robot noticed the following build errors:

[auto build test ERROR on linux-review/Yiqi-Sun/arm64-ptrace-use-live-x0-for-seccomp-and-audit-after-ptrace/20260815-210721]

url:    https://github.com/intel-lab-lkp/linux/commits/Will-Deacon/arm64-syscall-Ensure-saved-x0-is-kept-in-sync-with-tracer-updates/20260815-220235
base:   https://github.com/intel-lab-lkp/linux Yiqi-Sun/arm64-ptrace-use-live-x0-for-seccomp-and-audit-after-ptrace/20260815-210721
patch link:    https://lore.kernel.org/r/20260714143600.23853-1-will%40kernel.org
patch subject: [PATCH] arm64: syscall: Ensure saved x0 is kept in-sync with tracer updates
config: arm64-randconfig-001 (https://download.01.org/0day-ci/archive/20260820/202608201957.jszjEpsE-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 14.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260820/202608201957.jszjEpsE-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202608201957.jszjEpsE-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/arm64/kernel/ptrace.c:2461:13: error: conflicting types for 'update_syscall_orig_x0_after_ptrace'; have 'void(struct pt_regs *)'
    2461 | static void update_syscall_orig_x0_after_ptrace(struct pt_regs *regs)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/arm64/kernel/ptrace.c:563:13: note: previous definition of 'update_syscall_orig_x0_after_ptrace' with type 'void(struct task_struct *)'
     563 | static void update_syscall_orig_x0_after_ptrace(struct task_struct *target)
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +2461 arch/arm64/kernel/ptrace.c

  2460	
> 2461	static void update_syscall_orig_x0_after_ptrace(struct pt_regs *regs)
  2462	{
  2463		/*
  2464		 * Keep orig_x0 authoritative so that seccomp (via
  2465		 * syscall_get_arguments()), audit and the restart path all see the same
  2466		 * first argument the syscall is dispatched with, even if it has been
  2467		 * updated by a tracer. Skip this for NO_SYSCALL (set either by the user
  2468		 * or the tracer), as regs[0] holds the return value (see the comment in
  2469		 * el0_svc_common()) and can be unwound using syscall_rollback().
  2470		 * For compat tasks, orig_r0 is provided directly through GPR index 17.
  2471		 */
  2472		if (!is_compat_task() && regs->syscallno != NO_SYSCALL)
  2473			regs->orig_x0 = regs->regs[0];
  2474	}
  2475	

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