x86/entry: Remove debug IDT frobbing

This is all unused now.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.245019500@infradead.org

diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 3e1c5021d0f8d83bc1568fd059cc782c6740ba63..42fc35d865357040032bf6af149ae471abfa5051 100644 (file)
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -94,25 +94,6 @@ extern void aout_dump_debugregs(struct user *dump);
 
 extern void hw_breakpoint_restore(void);
 
-#ifdef CONFIG_X86_64
-DECLARE_PER_CPU(int, debug_stack_usage);
-static inline void debug_stack_usage_inc(void)
-{
-       __this_cpu_inc(debug_stack_usage);
-}
-static inline void debug_stack_usage_dec(void)
-{
-       __this_cpu_dec(debug_stack_usage);
-}
-void debug_stack_set_zero(void);
-void debug_stack_reset(void);
-#else /* !X86_64 */
-static inline void debug_stack_set_zero(void) { }
-static inline void debug_stack_reset(void) { }
-static inline void debug_stack_usage_inc(void) { }
-static inline void debug_stack_usage_dec(void) { }
-#endif /* X86_64 */
-
 static __always_inline unsigned long local_db_save(void)
 {
        unsigned long dr7;

diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index d6c3d346c63af42aeb266493a3173fda844f4303..07632f31147aed065dba883d296916916754cdc6 100644 (file)
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -42,8 +42,6 @@ static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *in
 
 extern struct desc_ptr idt_descr;
 extern gate_desc idt_table[];
-extern const struct desc_ptr debug_idt_descr;
-extern gate_desc debug_idt_table[];
 
 struct gdt_page {
        struct desc_struct gdt[GDT_ENTRIES];
@@ -390,31 +388,6 @@ void alloc_intr_gate(unsigned int n, const void *addr);
 
 extern unsigned long system_vectors[];
 
-#ifdef CONFIG_X86_64
-DECLARE_PER_CPU(u32, debug_idt_ctr);
-static __always_inline bool is_debug_idt_enabled(void)
-{
-       if (this_cpu_read(debug_idt_ctr))
-               return true;
-
-       return false;
-}
-
-static __always_inline void load_debug_idt(void)
-{
-       load_idt((const struct desc_ptr *)&debug_idt_descr);
-}
-#else
-static inline bool is_debug_idt_enabled(void)
-{
-       return false;
-}
-
-static inline void load_debug_idt(void)
-{
-}
-#endif
-
 /*
  * The load_current_idt() must be called with interrupts disabled
  * to avoid races. That way the IDT will always be set back to the expected
@@ -424,10 +397,7 @@ static inline void load_debug_idt(void)
  */
 static __always_inline void load_current_idt(void)
 {
-       if (is_debug_idt_enabled())
-               load_debug_idt();
-       else
-               load_idt((const struct desc_ptr *)&idt_descr);
+       load_idt((const struct desc_ptr *)&idt_descr);
 }
 
 extern void idt_setup_early_handler(void);
@@ -438,11 +408,9 @@ extern void idt_setup_apic_and_irq_gates(void);
 #ifdef CONFIG_X86_64
 extern void idt_setup_early_pf(void);
 extern void idt_setup_ist_traps(void);
-extern void idt_setup_debugidt_traps(void);
 #else
 static inline void idt_setup_early_pf(void) { }
 static inline void idt_setup_ist_traps(void) { }
-static inline void idt_setup_debugidt_traps(void) { }
 #endif
 
 extern void idt_invalidate(void *addr);

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f4645f9ff9cb555f0a6a0f64529abc69d3a31d24..043d93cdcaad29cf55e76072540fe34b7c72f0d5 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1706,23 +1706,6 @@ void syscall_init(void)
               X86_EFLAGS_IOPL|X86_EFLAGS_AC|X86_EFLAGS_NT);
 }
 
-DEFINE_PER_CPU(int, debug_stack_usage);
-DEFINE_PER_CPU(u32, debug_idt_ctr);
-
-noinstr void debug_stack_set_zero(void)
-{
-       this_cpu_inc(debug_idt_ctr);
-       load_current_idt();
-}
-
-noinstr void debug_stack_reset(void)
-{
-       if (WARN_ON(!this_cpu_read(debug_idt_ctr)))
-               return;
-       if (this_cpu_dec_return(debug_idt_ctr) == 0)
-               load_current_idt();
-}
-
 #else  /* CONFIG_X86_64 */
 
 DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;

diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index bc9b0d1d7bb8ace1c397c3e1981ec6e4207cea03..226c99229886591e724b2146ef3c830c9b8a6835 100644 (file)
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -158,14 +158,6 @@ static const __initconst struct idt_data apic_idts[] = {
 static const __initconst struct idt_data early_pf_idts[] = {
        INTG(X86_TRAP_PF,               asm_exc_page_fault),
 };
-
-/*
- * Override for the debug_idt. Same as the default, but with interrupt
- * stack set to DEFAULT_STACK (0). Required for NMI trap handling.
- */
-static const __initconst struct idt_data dbg_idts[] = {
-       INTG(X86_TRAP_DB,               asm_exc_debug),
-};
 #endif
 
 /* Must be page-aligned because the real IDT is used in a fixmap. */
@@ -177,9 +169,6 @@ struct desc_ptr idt_descr __ro_after_init = {
 };
 
 #ifdef CONFIG_X86_64
-/* No need to be aligned, but done to keep all IDTs defined the same way. */
-gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
-
 /*
  * The exceptions which use Interrupt stacks. They are setup after
  * cpu_init() when the TSS has been initialized.
@@ -192,15 +181,6 @@ static const __initconst struct idt_data ist_idts[] = {
        ISTG(X86_TRAP_MC,       asm_exc_machine_check,  IST_INDEX_MCE),
 #endif
 };
-
-/*
- * Override for the debug_idt. Same as the default, but with interrupt
- * stack set to DEFAULT_STACK (0). Required for NMI trap handling.
- */
-const struct desc_ptr debug_idt_descr = {
-       .size           = IDT_ENTRIES * 16 - 1,
-       .address        = (unsigned long) debug_idt_table,
-};
 #endif
 
 static inline void idt_init_desc(gate_desc *gate, const struct idt_data *d)
@@ -292,16 +272,6 @@ void __init idt_setup_ist_traps(void)
 {
        idt_setup_from_table(idt_table, ist_idts, ARRAY_SIZE(ist_idts), true);
 }
-
-/**
- * idt_setup_debugidt_traps - Initialize the debug idt table with debug traps
- */
-void __init idt_setup_debugidt_traps(void)
-{
-       memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16);
-
-       idt_setup_from_table(debug_idt_table, dbg_idts, ARRAY_SIZE(dbg_idts), false);
-}
 #endif
 
 /**

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index bcb9dd961c6d6011930c0c8f6a801f6c6d768cf2..6f887be1ac0c85691d127d3ed01f80a151ed5cf7 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -798,12 +798,6 @@ static void noinstr handle_debug(struct pt_regs *regs, unsigned long dr6,
                return;
        }
 
-       /*
-        * Let others (NMI) know that the debug stack is in use
-        * as we may switch to the interrupt stack.
-        */
-       debug_stack_usage_inc();
-
        /* It's safe to allow irq's after DR6 has been saved */
        cond_local_irq_enable(regs);
 
@@ -831,7 +825,6 @@ static void noinstr handle_debug(struct pt_regs *regs, unsigned long dr6,
 
 out:
        cond_local_irq_disable(regs);
-       debug_stack_usage_dec();
        instrumentation_end();
 }
 
@@ -1077,6 +1070,4 @@ void __init trap_init(void)
        cpu_init();
 
        idt_setup_ist_traps();
-
-       idt_setup_debugidt_traps();
 }