[PATCH 1/7] x86, kgdb: early trap init for early debug

[Jason Wessel]

From: Jan Kiszka <jan.kiszka@xxxxxx>

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

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxx>
Signed-off-by: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
---
 arch/x86/include/asm/processor.h |    2 ++
 arch/x86/kernel/setup.c          |    1 +
 arch/x86/kernel/traps.c          |   14 ++++++++++----
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b753ea5..543f48a 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -793,6 +793,8 @@ 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 c4851ef..e802989 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 7296bd2..94b604b 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -885,6 +885,16 @@ 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;
@@ -898,10 +908,7 @@ 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);
@@ -917,7 +924,6 @@ 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);
-- 
1.6.3.3

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