From 189382f7a338c02b448ab27e1d5566e052165dc8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9=20Fabian=20Silva=20Delgado?=
 <emulatorman@parabola.nu>
Date: Wed, 7 Dec 2016 16:30:11 -0300
Subject: Linux-libre 4.8.12-gnu

---
 arch/x86/events/intel/ds.c | 35 +++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 12 deletions(-)

(limited to 'arch/x86/events/intel/ds.c')

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 9b983a474..8fc714b4f 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1070,20 +1070,20 @@ static void setup_pebs_sample_data(struct perf_event *event,
 	}
 
 	/*
-	 * We use the interrupt regs as a base because the PEBS record
-	 * does not contain a full regs set, specifically it seems to
-	 * lack segment descriptors, which get used by things like
-	 * user_mode().
+	 * We use the interrupt regs as a base because the PEBS record does not
+	 * contain a full regs set, specifically it seems to lack segment
+	 * descriptors, which get used by things like user_mode().
 	 *
-	 * In the simple case fix up only the IP and BP,SP regs, for
-	 * PERF_SAMPLE_IP and PERF_SAMPLE_CALLCHAIN to function properly.
-	 * A possible PERF_SAMPLE_REGS will have to transfer all regs.
+	 * In the simple case fix up only the IP for PERF_SAMPLE_IP.
+	 *
+	 * We must however always use BP,SP from iregs for the unwinder to stay
+	 * sane; the record BP,SP can point into thin air when the record is
+	 * from a previous PMI context or an (I)RET happend between the record
+	 * and PMI.
 	 */
 	*regs = *iregs;
 	regs->flags = pebs->flags;
 	set_linear_ip(regs, pebs->ip);
-	regs->bp = pebs->bp;
-	regs->sp = pebs->sp;
 
 	if (sample_type & PERF_SAMPLE_REGS_INTR) {
 		regs->ax = pebs->ax;
@@ -1092,10 +1092,21 @@ static void setup_pebs_sample_data(struct perf_event *event,
 		regs->dx = pebs->dx;
 		regs->si = pebs->si;
 		regs->di = pebs->di;
-		regs->bp = pebs->bp;
-		regs->sp = pebs->sp;
 
-		regs->flags = pebs->flags;
+		/*
+		 * Per the above; only set BP,SP if we don't need callchains.
+		 *
+		 * XXX: does this make sense?
+		 */
+		if (!(sample_type & PERF_SAMPLE_CALLCHAIN)) {
+			regs->bp = pebs->bp;
+			regs->sp = pebs->sp;
+		}
+
+		/*
+		 * Preserve PERF_EFLAGS_VM from set_linear_ip().
+		 */
+		regs->flags = pebs->flags | (regs->flags & PERF_EFLAGS_VM);
 #ifndef CONFIG_X86_32
 		regs->r8 = pebs->r8;
 		regs->r9 = pebs->r9;
-- 
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