x86, kgdb: early trap init for early debug

Allow the x86 arch to have early exception processing for the purpose
of debugging via the kgdb.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

3 files changed, 13 insertions, 4 deletions

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 5a51379dcbe4..7e5c6a60b8ee 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -789,6 +789,8 @@ static inline void wbinvd_halt(void)
 extern void enable_sep_cpu(void);
 extern int sysenter_setup(void);
 
+extern void early_trap_init(void);
+
 /* Defined in head.S */
 extern struct desc_ptr          early_gdt_descr;
 
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index c4851eff57b3..e8029896309a 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -725,6 +725,7 @@ void __init setup_arch(char **cmdline_p)
         /* VMI may relocate the fixmap; do this before touching ioremap area */
         vmi_init();
 
+        early_trap_init();
         early_cpu_init();
         early_ioremap_init();
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 7eaad4c5110a..142d70c74b02 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -808,6 +808,16 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
 }
 #endif
 
+/* Set of traps needed for early debugging. */
+void __init early_trap_init(void)
+{
+        set_intr_gate_ist(1, &debug, DEBUG_STACK);
+        /* int3 can be called from all */
+        set_system_intr_gate_ist(3, &int3, DEBUG_STACK);
+        set_intr_gate(14, &page_fault);
+        load_idt(&idt_descr);
+}
+
 void __init trap_init(void)
 {
         int i;
@@ -821,10 +831,7 @@ void __init trap_init(void)
 #endif
 
         set_intr_gate(0, &divide_error);
-        set_intr_gate_ist(1, &debug, DEBUG_STACK);
         set_intr_gate_ist(2, &nmi, NMI_STACK);
-        /* int3 can be called from all */
-        set_system_intr_gate_ist(3, &int3, DEBUG_STACK);
         /* int4 can be called from all */
         set_system_intr_gate(4, &overflow);
         set_intr_gate(5, &bounds);
@@ -840,7 +847,6 @@ void __init trap_init(void)
         set_intr_gate(11, &segment_not_present);
         set_intr_gate_ist(12, &stack_segment, STACKFAULT_STACK);
         set_intr_gate(13, &general_protection);
-        set_intr_gate(14, &page_fault);
         set_intr_gate(15, &spurious_interrupt_bug);
         set_intr_gate(16, &coprocessor_error);
         set_intr_gate(17, &alignment_check);