Convert #AC to IDTENTRY_ERRORCODE:
  - Implement the C entry point with DEFINE_IDTENTRY
  - Emit the ASM stub with DECLARE_IDTENTRY
  - Remove the ASM idtentry in 64bit
  - Remove the open coded ASM entry code in 32bit
  - Fixup the XEN/PV code
  - Remove the old prototypes
  - Remove the RCU warning as the new entry macro ensures correctness
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134905.928967113@linutronix.de
 SYM_CODE_END(native_iret)
 #endif
 
-SYM_CODE_START(alignment_check)
-       ASM_CLAC
-       pushl   $do_alignment_check
-       jmp     common_exception
-SYM_CODE_END(alignment_check)
-
 #ifdef CONFIG_X86_MCE
 SYM_CODE_START(machine_check)
        ASM_CLAC
 
  */
 
 idtentry       X86_TRAP_BP             int3                    do_int3                         has_error_code=0
-idtentry       X86_TRAP_AC             alignment_check         do_alignment_check              has_error_code=1
 idtentry       X86_TRAP_XF             simd_coprocessor_error  do_simd_coprocessor_error       has_error_code=0
 
 idtentry       X86_TRAP_PF             page_fault              do_page_fault                   has_error_code=1
 
 DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_NP,        exc_segment_not_present);
 DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_SS,        exc_stack_segment);
 DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_GP,        exc_general_protection);
+DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_AC,        exc_alignment_check);
 
 #endif
 
 #endif
 asmlinkage void page_fault(void);
 asmlinkage void async_page_fault(void);
-asmlinkage void alignment_check(void);
 #ifdef CONFIG_X86_MCE
 asmlinkage void machine_check(void);
 #endif /* CONFIG_X86_MCE */
 asmlinkage void xen_int3(void);
 asmlinkage void xen_double_fault(void);
 asmlinkage void xen_page_fault(void);
-asmlinkage void xen_alignment_check(void);
 #ifdef CONFIG_X86_MCE
 asmlinkage void xen_machine_check(void);
 #endif /* CONFIG_X86_MCE */
 dotraplinkage void do_int3(struct pt_regs *regs, long error_code);
 dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long cr2);
 dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address);
-dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code);
 dotraplinkage void do_simd_coprocessor_error(struct pt_regs *regs, long error_code);
 #ifdef CONFIG_X86_32
 dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code);
 
        INTG(X86_TRAP_GP,               asm_exc_general_protection),
        INTG(X86_TRAP_SPURIOUS,         asm_exc_spurious_interrupt_bug),
        INTG(X86_TRAP_MF,               asm_exc_coprocessor_error),
-       INTG(X86_TRAP_AC,               alignment_check),
+       INTG(X86_TRAP_AC,               asm_exc_alignment_check),
        INTG(X86_TRAP_XF,               simd_coprocessor_error),
 
 #ifdef CONFIG_X86_32
 
                      0, NULL);
 }
 
-dotraplinkage void do_alignment_check(struct pt_regs *regs, long error_code)
+DEFINE_IDTENTRY_ERRORCODE(exc_alignment_check)
 {
        char *str = "alignment check";
 
-       RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
-
        if (notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_AC, SIGBUS) == NOTIFY_STOP)
                return;
 
 
        TRAP_ENTRY(exc_general_protection,              false ),
        TRAP_ENTRY(exc_spurious_interrupt_bug,          false ),
        TRAP_ENTRY(exc_coprocessor_error,               false ),
-       { alignment_check,             xen_alignment_check,             false },
+       TRAP_ENTRY(exc_alignment_check,                 false ),
        { simd_coprocessor_error,      xen_simd_coprocessor_error,      false },
 };
 
 
 xen_pv_trap page_fault
 xen_pv_trap asm_exc_spurious_interrupt_bug
 xen_pv_trap asm_exc_coprocessor_error
-xen_pv_trap alignment_check
+xen_pv_trap asm_exc_alignment_check
 #ifdef CONFIG_X86_MCE
 xen_pv_trap machine_check
 #endif /* CONFIG_X86_MCE */