Dump last branch information on oopses

Signed-off-by: Andi Kleen <ak@suse.de>

Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -692,8 +692,38 @@ END(spurious_interrupt)
 /*
  * Exception entry points.
  */ 		
+
+	.macro savemsr msr,var
+	movl  $\msr,%ecx
+	rdmsr
+	movl %eax,\var
+	movl %edx,\var+4
+	.endm
+
+	.macro SAVELBR
+	cmpl $0,netburst
+	jz 1f
+	push %rax
+	push %rdx
+	push %rcx
+	savemsr 0x1da,lbr_tos
+	savemsr 0x1d7,ler_from
+	savemsr 0x1d8,ler_to
+	.set cnt,0
+	.rept 16
+	savemsr 0x680+cnt,lbr_from+cnt*8
+	savemsr 0x6c0+cnt,lbr_to+cnt*8
+	.set cnt,cnt+1
+	.endr 
+	pop %rcx
+	pop %rdx
+	pop %rax
+1:
+	.endm
+
 	.macro zeroentry sym
 	INTR_FRAME
+	SAVELBR
 	pushq $0	/* push error code/oldrax */ 
 	CFI_ADJUST_CFA_OFFSET 8
 	pushq %rax	/* push real oldrax to the rdi slot */ 
@@ -705,6 +735,7 @@ END(spurious_interrupt)
 
 	.macro errorentry sym
 	XCPT_FRAME
+	SAVELBR
 	pushq %rax
 	CFI_ADJUST_CFA_OFFSET 8
 	leaq  \sym(%rip),%rax
@@ -715,6 +746,7 @@ END(spurious_interrupt)
 	/* error code is on the stack already */
 	/* handle NMI like exceptions that can happen everywhere */
 	.macro paranoidentry sym, ist=0, irqtrace=1
+	SAVELBR
 	SAVE_ALL
 	cld
 	movl $1,%ebx
Index: linux/arch/x86_64/kernel/setup.c
===================================================================
--- linux.orig/arch/x86_64/kernel/setup.c
+++ linux/arch/x86_64/kernel/setup.c
@@ -822,10 +822,13 @@ static void srat_detect_node(void)
 #endif
 }
 
+int netburst;
+
 static void __cpuinit init_intel(struct cpuinfo_x86 *c)
 {
 	/* Cache sizes */
 	unsigned n;
+	unsigned long val;
 
 	init_intel_cacheinfo(c);
 	if (c->cpuid_level > 9 ) {
@@ -867,6 +870,12 @@ static void __cpuinit init_intel(struct 
  	c->x86_max_cores = intel_num_cpu_cores(c);
 
 	srat_detect_node();
+
+	if (c->x86 == 15) { 
+		rdmsrl(MSR_IA32_DEBUGCTLMSR, val);
+		wrmsrl(MSR_IA32_DEBUGCTLMSR, val | 1);
+		netburst = 1;
+	}
 }
 
 static void __cpuinit get_cpu_vendor(struct cpuinfo_x86 *c)
Index: linux/arch/x86_64/kernel/process.c
===================================================================
--- linux.orig/arch/x86_64/kernel/process.c
+++ linux/arch/x86_64/kernel/process.c
@@ -36,6 +36,7 @@
 #include <linux/random.h>
 #include <linux/notifier.h>
 #include <linux/kprobes.h>
+#include <linux/kallsyms.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -278,6 +279,9 @@ static int __init idle_setup (char *str)
 
 __setup("idle=", idle_setup);
 
+unsigned long lbr_tos, lbr_from[16], lbr_to[16], ler_from, ler_to;
+extern int netburst;
+
 /* Prints also some state that isn't saved in the pt_regs */ 
 void __show_regs(struct pt_regs * regs)
 {
@@ -326,6 +330,18 @@ void __show_regs(struct pt_regs * regs)
 	       fs,fsindex,gs,gsindex,shadowgs); 
 	printk("CS:  %04x DS: %04x ES: %04x CR0: %016lx\n", cs, ds, es, cr0); 
 	printk("CR2: %016lx CR3: %016lx CR4: %016lx\n", cr2, cr3, cr4);
+
+	if (netburst) { 
+		unsigned i;
+		printk("LBR: TOS %lx", lbr_tos);
+		print_symbol(" LER_FROM %s", ler_from);
+		print_symbol(" LER_TO %s\n", ler_to);
+		for (i = 0; i < 16; i++) { 
+			printk("    [%d]", i);
+			print_symbol(" FROM %s", lbr_from[i]);
+			print_symbol(" TO %s\n", lbr_from[i]);
+		}
+	}
 }
 
 void show_regs(struct pt_regs *regs)