x86/entry: Convert Debug exception to IDTENTRY_DB

Convert #DB to IDTENTRY_ERRORCODE:
  - Implement the C entry point with DEFINE_IDTENTRY_DB
  - 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

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/20200505135314.900297476@linutronix.de

2 files changed, 17 insertions, 12 deletions

diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index d3fecd88677c..ddf3f3db3235 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -59,7 +59,7 @@ static bool idt_setup_done __initdata;
  * stacks work only after cpu_init().
  */
 static const __initconst struct idt_data early_idts[] = {
-	INTG(X86_TRAP_DB,		debug),
+	INTG(X86_TRAP_DB,		asm_exc_debug),
 	SYSG(X86_TRAP_BP,		asm_exc_int3),
 #ifdef CONFIG_X86_32
 	INTG(X86_TRAP_PF,		page_fault),
@@ -93,7 +93,7 @@ static const __initconst struct idt_data def_idts[] = {
 #else
 	INTG(X86_TRAP_DF,		double_fault),
 #endif
-	INTG(X86_TRAP_DB,		debug),
+	INTG(X86_TRAP_DB,		asm_exc_debug),
 
 #ifdef CONFIG_X86_MCE
 	INTG(X86_TRAP_MC,		asm_exc_machine_check),
@@ -164,7 +164,7 @@ static const __initconst struct idt_data early_pf_idts[] = {
  * stack set to DEFAULT_STACK (0). Required for NMI trap handling.
  */
 static const __initconst struct idt_data dbg_idts[] = {
-	INTG(X86_TRAP_DB,	debug),
+	INTG(X86_TRAP_DB,		asm_exc_debug),
 };
 #endif
 
@@ -185,7 +185,7 @@ gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
  * cpu_init() when the TSS has been initialized.
  */
 static const __initconst struct idt_data ist_idts[] = {
-	ISTG(X86_TRAP_DB,	debug,			IST_INDEX_DB),
+	ISTG(X86_TRAP_DB,	asm_exc_debug,		IST_INDEX_DB),
 	ISTG(X86_TRAP_NMI,	asm_exc_nmi,		IST_INDEX_NMI),
 	ISTG(X86_TRAP_DF,	double_fault,		IST_INDEX_DF),
 #ifdef CONFIG_X86_MCE
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index de5120e2fbe1..569408a681b6 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -775,7 +775,7 @@ static __always_inline void debug_exit(unsigned long dr7)
  *
  * May run on IST stack.
  */
-dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
+DEFINE_IDTENTRY_DEBUG(exc_debug)
 {
 	struct task_struct *tsk = current;
 	unsigned long dr6, dr7;
@@ -784,7 +784,10 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
 
 	debug_enter(&dr6, &dr7);
 
-	nmi_enter();
+	if (user_mode(regs))
+		idtentry_enter(regs);
+	else
+		nmi_enter();
 
 	/*
 	 * The SDM says "The processor clears the BTF flag when it
@@ -821,7 +824,7 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
 		goto exit;
 #endif
 
-	if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, error_code,
+	if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0,
 		       SIGTRAP) == NOTIFY_STOP)
 		goto exit;
 
@@ -835,8 +838,8 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
 	cond_local_irq_enable(regs);
 
 	if (v8086_mode(regs)) {
-		handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code,
-					X86_TRAP_DB);
+		handle_vm86_trap((struct kernel_vm86_regs *) regs, 0,
+				 X86_TRAP_DB);
 		cond_local_irq_disable(regs);
 		debug_stack_usage_dec();
 		goto exit;
@@ -855,15 +858,17 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
 	}
 	si_code = get_si_code(tsk->thread.debugreg6);
 	if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp)
-		send_sigtrap(regs, error_code, si_code);
+		send_sigtrap(regs, 0, si_code);
 	cond_local_irq_disable(regs);
 	debug_stack_usage_dec();
 
 exit:
-	nmi_exit();
+	if (user_mode(regs))
+		idtentry_exit(regs);
+	else
+		nmi_exit();
 	debug_exit(dr7);
 }
-NOKPROBE_SYMBOL(do_debug);
 
 /*
  * Note that we play around with the 'TS' bit in an attempt to get