X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?p=kvmfornfv.git;a=blobdiff_plain;f=kernel%2Farch%2Fx86%2Fkernel%2Fcpu%2Fperf_event.c;h=4cc98a4e8ea950955cf6440e558a730e105a8020;hp=aa4e3a74e5410e43cbb7fb322e06dbea040acbb6;hb=ec0a2ed6d8a5e555edef907895c041e285fdb495;hpb=342fa5dfa053559f47caad657132522496dcf1b3

diff --git a/kernel/arch/x86/kernel/cpu/perf_event.c b/kernel/arch/x86/kernel/cpu/perf_event.c
index aa4e3a74e..4cc98a4e8 100644
--- a/kernel/arch/x86/kernel/cpu/perf_event.c
+++ b/kernel/arch/x86/kernel/cpu/perf_event.c
@@ -2170,21 +2170,25 @@ static unsigned long get_segment_base(unsigned int segment)
 	int idx = segment >> 3;
 
 	if ((segment & SEGMENT_TI_MASK) == SEGMENT_LDT) {
+		struct ldt_struct *ldt;
+
 		if (idx > LDT_ENTRIES)
 			return 0;
 
-		if (idx > current->active_mm->context.size)
+		/* IRQs are off, so this synchronizes with smp_store_release */
+		ldt = lockless_dereference(current->active_mm->context.ldt);
+		if (!ldt || idx > ldt->size)
 			return 0;
 
-		desc = current->active_mm->context.ldt;
+		desc = &ldt->entries[idx];
 	} else {
 		if (idx > GDT_ENTRIES)
 			return 0;
 
-		desc = raw_cpu_ptr(gdt_page.gdt);
+		desc = raw_cpu_ptr(gdt_page.gdt) + idx;
 	}
 
-	return get_desc_base(desc + idx);
+	return get_desc_base(desc);
 }
 
 #ifdef CONFIG_COMPAT