x86/entry: Convert Divide Error to IDTENTRY

Convert #DE to IDTENTRY:
  - 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

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/20200505134904.663914713@linutronix.de

arch/x86/entry/entry_32.S

@@ -1377,13 +1377,6 @@ SYM_CODE_START(alignment_check)
 	jmp	common_exception
 SYM_CODE_END(alignment_check)
 
-SYM_CODE_START(divide_error)
-	ASM_CLAC
-	pushl	$0				# no error code
-	pushl	$do_divide_error
-	jmp	common_exception
-SYM_CODE_END(divide_error)
-
 #ifdef CONFIG_X86_MCE
 SYM_CODE_START(machine_check)
 	ASM_CLAC

arch/x86/entry/entry_64.S

@@ -1072,7 +1072,6 @@ apicinterrupt IRQ_WORK_VECTOR			irq_work_interrupt		smp_irq_work_interrupt
  * Exception entry points.
  */
 
-idtentry	X86_TRAP_DE		divide_error		do_divide_error			has_error_code=0
 idtentry	X86_TRAP_OF		overflow		do_overflow			has_error_code=0
 idtentry	X86_TRAP_BP		int3			do_int3				has_error_code=0
 idtentry	X86_TRAP_BR		bounds			do_bounds			has_error_code=0

arch/x86/include/asm/idtentry.h

@@ -67,4 +67,16 @@ static __always_inline void __##func(struct pt_regs *regs)
 
 #endif /* __ASSEMBLY__ */
 
+/*
+ * The actual entry points. Note that DECLARE_IDTENTRY*() serves two
+ * purposes:
+ *  - provide the function declarations when included from C-Code
+ *  - emit the ASM stubs when included from entry_32/64.S
+ *
+ * This avoids duplicate defines and ensures that everything is consistent.
+ */
+
+/* Simple exception entry points. No hardware error code */
+DECLARE_IDTENTRY(X86_TRAP_DE,		exc_divide_error);
+
 #endif

arch/x86/include/asm/traps.h

@@ -11,7 +11,6 @@
 
 #define dotraplinkage __visible
 
-asmlinkage void divide_error(void);
 asmlinkage void debug(void);
 asmlinkage void nmi(void);
 asmlinkage void int3(void);
@@ -38,7 +37,6 @@ asmlinkage void machine_check(void);
 asmlinkage void simd_coprocessor_error(void);
 
 #if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
-asmlinkage void xen_divide_error(void);
 asmlinkage void xen_xennmi(void);
 asmlinkage void xen_xendebug(void);
 asmlinkage void xen_int3(void);
@@ -62,7 +60,6 @@ asmlinkage void xen_machine_check(void);
 asmlinkage void xen_simd_coprocessor_error(void);
 #endif
 
-dotraplinkage void do_divide_error(struct pt_regs *regs, long error_code);
 dotraplinkage void do_debug(struct pt_regs *regs, long error_code);
 dotraplinkage void do_nmi(struct pt_regs *regs, long error_code);
 dotraplinkage void do_int3(struct pt_regs *regs, long error_code);

arch/x86/kernel/idt.c

@@ -73,7 +73,7 @@ static const __initconst struct idt_data early_idts[] = {
  * set up TSS.
  */
 static const __initconst struct idt_data def_idts[] = {
-	INTG(X86_TRAP_DE,		divide_error),
+	INTG(X86_TRAP_DE,		asm_exc_divide_error),
 	INTG(X86_TRAP_NMI,		nmi),
 	INTG(X86_TRAP_BR,		bounds),
 	INTG(X86_TRAP_UD,		invalid_op),

arch/x86/kernel/traps.c

@@ -220,6 +220,12 @@ static __always_inline void __user *error_get_trap_addr(struct pt_regs *regs)
 	return (void __user *)uprobe_get_trap_addr(regs);
 }
 
+DEFINE_IDTENTRY(exc_divide_error)
+{
+	do_error_trap(regs, 0, "divide_error", X86_TRAP_DE, SIGFPE,
+		      FPE_INTDIV, error_get_trap_addr(regs));
+}
+
 #define IP ((void __user *)uprobe_get_trap_addr(regs))
 #define DO_ERROR(trapnr, signr, sicode, addr, str, name)		   \
 dotraplinkage void do_##name(struct pt_regs *regs, long error_code)	   \
@@ -227,7 +233,6 @@ dotraplinkage void do_##name(struct pt_regs *regs, long error_code)	   \
 	do_error_trap(regs, error_code, str, trapnr, signr, sicode, addr); \
 }
 
-DO_ERROR(X86_TRAP_DE,     SIGFPE,  FPE_INTDIV,   IP, "divide error",        divide_error)
 DO_ERROR(X86_TRAP_OF,     SIGSEGV,          0, NULL, "overflow",            overflow)
 DO_ERROR(X86_TRAP_UD,     SIGILL,  ILL_ILLOPN,   IP, "invalid opcode",      invalid_op)
 DO_ERROR(X86_TRAP_OLD_MF, SIGFPE,           0, NULL, "coprocessor segment overrun", coprocessor_segment_overrun)

arch/x86/xen/enlighten_pv.c

@@ -604,6 +604,11 @@ struct trap_array_entry {
 	bool ist_okay;
 };
 
+#define TRAP_ENTRY(func, ist_ok) {			\
+	.orig		= asm_##func,			\
+	.xen		= xen_asm_##func,		\
+	.ist_okay	= ist_ok }
+
 static struct trap_array_entry trap_array[] = {
 	{ debug,                       xen_xendebug,                    true },
 	{ double_fault,                xen_double_fault,                true },
@@ -617,7 +622,7 @@ static struct trap_array_entry trap_array[] = {
 	{ entry_INT80_compat,          xen_entry_INT80_compat,          false },
 #endif
 	{ page_fault,                  xen_page_fault,                  false },
-	{ divide_error,                xen_divide_error,                false },
+	TRAP_ENTRY(exc_divide_error,			false ),
 	{ bounds,                      xen_bounds,                      false },
 	{ invalid_op,                  xen_invalid_op,                  false },
 	{ device_not_available,        xen_device_not_available,        false },

arch/x86/xen/xen-asm_64.S

@@ -28,7 +28,7 @@ SYM_CODE_END(xen_\name)
 _ASM_NOKPROBE(xen_\name)
 .endm
 
-xen_pv_trap divide_error
+xen_pv_trap asm_exc_divide_error
 xen_pv_trap debug
 xen_pv_trap xendebug
 xen_pv_trap int3