5 files changed, 114 insertions, 17 deletions

diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index dab39350e51..cb4e43bce98 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -196,11 +196,16 @@ static inline u32 get_ibs_caps(void) { return 0; }
 extern void perf_events_lapic_init(void);
 
 /*
- * Abuse bit 3 of the cpu eflags register to indicate proper PEBS IP fixups.
- * This flag is otherwise unused and ABI specified to be 0, so nobody should
- * care what we do with it.
+ * Abuse bits {3,5} of the cpu eflags register. These flags are otherwise
+ * unused and ABI specified to be 0, so nobody should care what we do with
+ * them.
+ *
+ * EXACT - the IP points to the exact instruction that triggered the
+ *         event (HW bugs exempt).
+ * VM    - original X86_VM_MASK; see set_linear_ip().
  */
 #define PERF_EFLAGS_EXACT	(1UL << 3)
+#define PERF_EFLAGS_VM		(1UL << 5)
 
 struct pt_regs;
 extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 29557aa06dd..915b876edd1 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -32,6 +32,8 @@
 #include <asm/smp.h>
 #include <asm/alternative.h>
 #include <asm/timer.h>
+#include <asm/desc.h>
+#include <asm/ldt.h>
 
 #include "perf_event.h"
 
@@ -1738,6 +1740,29 @@ valid_user_frame(const void __user *fp, unsigned long size)
 	return (__range_not_ok(fp, size, TASK_SIZE) == 0);
 }
 
+static unsigned long get_segment_base(unsigned int segment)
+{
+	struct desc_struct *desc;
+	int idx = segment >> 3;
+
+	if ((segment & SEGMENT_TI_MASK) == SEGMENT_LDT) {
+		if (idx > LDT_ENTRIES)
+			return 0;
+
+		if (idx > current->active_mm->context.size)
+			return 0;
+
+		desc = current->active_mm->context.ldt;
+	} else {
+		if (idx > GDT_ENTRIES)
+			return 0;
+
+		desc = __this_cpu_ptr(&gdt_page.gdt[0]);
+	}
+
+	return get_desc_base(desc + idx);
+}
+
 #ifdef CONFIG_COMPAT
 
 #include <asm/compat.h>
@@ -1746,13 +1771,17 @@ static inline int
 perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
 {
 	/* 32-bit process in 64-bit kernel. */
+	unsigned long ss_base, cs_base;
 	struct stack_frame_ia32 frame;
 	const void __user *fp;
 
 	if (!test_thread_flag(TIF_IA32))
 		return 0;
 
-	fp = compat_ptr(regs->bp);
+	cs_base = get_segment_base(regs->cs);
+	ss_base = get_segment_base(regs->ss);
+
+	fp = compat_ptr(ss_base + regs->bp);
 	while (entry->nr < PERF_MAX_STACK_DEPTH) {
 		unsigned long bytes;
 		frame.next_frame     = 0;
@@ -1765,8 +1794,8 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
 		if (!valid_user_frame(fp, sizeof(frame)))
 			break;
 
-		perf_callchain_store(entry, frame.return_address);
-		fp = compat_ptr(frame.next_frame);
+		perf_callchain_store(entry, cs_base + frame.return_address);
+		fp = compat_ptr(ss_base + frame.next_frame);
 	}
 	return 1;
 }
@@ -1789,6 +1818,12 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 		return;
 	}
 
+	/*
+	 * We don't know what to do with VM86 stacks.. ignore them for now.
+	 */
+	if (regs->flags & (X86_VM_MASK | PERF_EFLAGS_VM))
+		return;
+
 	fp = (void __user *)regs->bp;
 
 	perf_callchain_store(entry, regs->ip);
@@ -1816,16 +1851,50 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 	}
 }
 
-unsigned long perf_instruction_pointer(struct pt_regs *regs)
+/*
+ * Deal with code segment offsets for the various execution modes:
+ *
+ *   VM86 - the good olde 16 bit days, where the linear address is
+ *          20 bits and we use regs->ip + 0x10 * regs->cs.
+ *
+ *   IA32 - Where we need to look at GDT/LDT segment descriptor tables
+ *          to figure out what the 32bit base address is.
+ *
+ *    X32 - has TIF_X32 set, but is running in x86_64
+ *
+ * X86_64 - CS,DS,SS,ES are all zero based.
+ */
+static unsigned long code_segment_base(struct pt_regs *regs)
 {
-	unsigned long ip;
+	/*
+	 * If we are in VM86 mode, add the segment offset to convert to a
+	 * linear address.
+	 */
+	if (regs->flags & X86_VM_MASK)
+		return 0x10 * regs->cs;
+
+	/*
+	 * For IA32 we look at the GDT/LDT segment base to convert the
+	 * effective IP to a linear address.
+	 */
+#ifdef CONFIG_X86_32
+	if (user_mode(regs) && regs->cs != __USER_CS)
+		return get_segment_base(regs->cs);
+#else
+	if (test_thread_flag(TIF_IA32)) {
+		if (user_mode(regs) && regs->cs != __USER32_CS)
+			return get_segment_base(regs->cs);
+	}
+#endif
+	return 0;
+}
 
+unsigned long perf_instruction_pointer(struct pt_regs *regs)
+{
 	if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
-		ip = perf_guest_cbs->get_guest_ip();
-	else
-		ip = instruction_pointer(regs);
+		return perf_guest_cbs->get_guest_ip();
 
-	return ip;
+	return regs->ip + code_segment_base(regs);
 }
 
 unsigned long perf_misc_flags(struct pt_regs *regs)
@@ -1838,7 +1907,7 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
 		else
 			misc |= PERF_RECORD_MISC_GUEST_KERNEL;
 	} else {
-		if (!kernel_ip(regs->ip))
+		if (user_mode(regs))
 			misc |= PERF_RECORD_MISC_USER;
 		else
 			misc |= PERF_RECORD_MISC_KERNEL;
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index 821d53b696d..6605a81ba33 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -516,6 +516,26 @@ static inline bool kernel_ip(unsigned long ip)
 #endif
 }
 
+/*
+ * Not all PMUs provide the right context information to place the reported IP
+ * into full context. Specifically segment registers are typically not
+ * supplied.
+ *
+ * Assuming the address is a linear address (it is for IBS), we fake the CS and
+ * vm86 mode using the known zero-based code segment and 'fix up' the registers
+ * to reflect this.
+ *
+ * Intel PEBS/LBR appear to typically provide the effective address, nothing
+ * much we can do about that but pray and treat it like a linear address.
+ */
+static inline void set_linear_ip(struct pt_regs *regs, unsigned long ip)
+{
+	regs->cs = kernel_ip(ip) ? __KERNEL_CS : __USER_CS;
+	if (regs->flags & X86_VM_MASK)
+		regs->flags ^= (PERF_EFLAGS_VM | X86_VM_MASK);
+	regs->ip = ip;
+}
+
 #ifdef CONFIG_CPU_SUP_AMD
 
 int amd_pmu_init(void);
diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index da9bcdcd985..7bfb5bec863 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -13,6 +13,8 @@
 
 #include <asm/apic.h>
 
+#include "perf_event.h"
+
 static u32 ibs_caps;
 
 #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_AMD)
@@ -536,7 +538,7 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
 	if (check_rip && (ibs_data.regs[2] & IBS_RIP_INVALID)) {
 		regs.flags &= ~PERF_EFLAGS_EXACT;
 	} else {
-		instruction_pointer_set(&regs, ibs_data.regs[1]);
+		set_linear_ip(&regs, ibs_data.regs[1]);
 		regs.flags |= PERF_EFLAGS_EXACT;
 	}
 
diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index 629ae0b7ad9..e38d97bf425 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -499,7 +499,7 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
 	 * We sampled a branch insn, rewind using the LBR stack
 	 */
 	if (ip == to) {
-		regs->ip = from;
+		set_linear_ip(regs, from);
 		return 1;
 	}
 
@@ -529,7 +529,7 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
 	} while (to < ip);
 
 	if (to == ip) {
-		regs->ip = old_to;
+		set_linear_ip(regs, old_to);
 		return 1;
 	}
 
@@ -569,7 +569,8 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
 	 * A possible PERF_SAMPLE_REGS will have to transfer all regs.
 	 */
 	regs = *iregs;
-	regs.ip = pebs->ip;
+	regs.flags = pebs->flags;
+	set_linear_ip(&regs, pebs->ip);
 	regs.bp = pebs->bp;
 	regs.sp = pebs->sp;