Add support for cross double fault frames in stack traces:

- Populate the register values for the trapframe put on the stack by the
  double fault handler.
- Teach DDB's trace routine to treat a double fault like other trap frames.

MFC after:	3 days

4 files changed, 26 insertions, 5 deletions

diff --git a/sys/amd64/amd64/db_trace.c b/sys/amd64/amd64/db_trace.c
index 880be61..548c36c 100644
--- a/sys/amd64/amd64/db_trace.c
+++ b/sys/amd64/amd64/db_trace.c
@@ -317,7 +317,8 @@ db_nextframe(struct amd64_frame **fp, db_addr_t *ip, struct thread *td)
 	if (name != NULL) {
 		if (strcmp(name, "calltrap") == 0 ||
 		    strcmp(name, "fork_trampoline") == 0 ||
-		    strcmp(name, "nmi_calltrap") == 0)
+		    strcmp(name, "nmi_calltrap") == 0 ||
+		    strcmp(name, "Xdblfault") == 0)
 			frame_type = TRAP;
 		else if (strncmp(name, "Xatpic_intr", 11) == 0 ||
 		    strncmp(name, "Xapic_isr", 9) == 0 ||
diff --git a/sys/amd64/amd64/exception.S b/sys/amd64/amd64/exception.S
index 20e8c3d..da4918a 100644
--- a/sys/amd64/amd64/exception.S
+++ b/sys/amd64/amd64/exception.S
@@ -187,10 +187,28 @@ alltraps_noen:
 IDTVEC(dblfault)
 	subq	$TF_ERR,%rsp
 	movq	$T_DOUBLEFLT,TF_TRAPNO(%rsp)
+	movq	$0,TF_ADDR(%rsp)
+	movq	$0,TF_ERR(%rsp)
+	movq	%rdi,TF_RDI(%rsp)
+	movq	%rsi,TF_RSI(%rsp)
+	movq	%rdx,TF_RDX(%rsp)
+	movq	%rcx,TF_RCX(%rsp)
+	movq	%r8,TF_R8(%rsp)
+	movq	%r9,TF_R9(%rsp)
+	movq	%rax,TF_RAX(%rsp)
+	movq	%rbx,TF_RBX(%rsp)
+	movq	%rbp,TF_RBP(%rsp)
+	movq	%r10,TF_R10(%rsp)
+	movq	%r11,TF_R11(%rsp)
+	movq	%r12,TF_R12(%rsp)
+	movq	%r13,TF_R13(%rsp)
+	movq	%r14,TF_R14(%rsp)
+	movq	%r15,TF_R15(%rsp)
 	testb	$SEL_RPL_MASK,TF_CS(%rsp) /* Did we come from kernel? */
 	jz	1f			/* already running with kernel GS.base */
 	swapgs
-1:	call	dblfault_handler
+1:	movq	%rsp, %rdi
+	call	dblfault_handler
 2:	hlt
 	jmp	2b
 
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index b1d9637..1928518 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -138,7 +138,6 @@ __FBSDID("$FreeBSD$");
 CTASSERT(offsetof(struct pcpu, pc_curthread) == 0);
 
 extern u_int64_t hammer_time(u_int64_t, u_int64_t);
-extern void dblfault_handler(void);
 
 extern void printcpuinfo(void);	/* XXX header file */
 extern void identify_cpu(void);
diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index be6ffff..2ce8ed4 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -96,10 +96,10 @@ __FBSDID("$FreeBSD$");
 
 extern void trap(struct trapframe *frame);
 extern void syscall(struct trapframe *frame);
+void dblfault_handler(struct trapframe *frame);
 
 static int trap_pfault(struct trapframe *, int);
 static void trap_fatal(struct trapframe *, vm_offset_t);
-void dblfault_handler(void);
 
 #define MAX_TRAP_MSG		30
 static char *trap_msg[] = {
@@ -706,9 +706,12 @@ trap_fatal(frame, eva)
  * for example).
  */
 void
-dblfault_handler()
+dblfault_handler(struct trapframe *frame)
 {
 	printf("\nFatal double fault\n");
+	printf("rip = 0x%lx\n", frame->tf_rip);
+	printf("rsp = 0x%lx\n", frame->tf_rsp);
+	printf("rbp = 0x%lx\n", frame->tf_rbp);
 #ifdef SMP
 	/* two separate prints in case of a trap on an unmapped page */
 	printf("cpuid = %d; ", PCPU_GET(cpuid));