From e2760839033618410cdea9aeab039e096cde54be Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@google.com>
Date: Thu, 27 Jun 2019 13:23:49 -0700
Subject: gvisor/ptrace: grub initial thread registers only once

PiperOrigin-RevId: 255465635
---
 pkg/sentry/platform/ptrace/subprocess.go       | 4 ++++
 pkg/sentry/platform/ptrace/subprocess_linux.go | 1 +
 2 files changed, 5 insertions(+)

(limited to 'pkg/sentry/platform/ptrace')

diff --git a/pkg/sentry/platform/ptrace/subprocess.go b/pkg/sentry/platform/ptrace/subprocess.go
index f15b3415a..46f9d3fb6 100644
--- a/pkg/sentry/platform/ptrace/subprocess.go
+++ b/pkg/sentry/platform/ptrace/subprocess.go
@@ -155,6 +155,7 @@ func newSubprocess(create func() (*thread, error)) (*subprocess, error) {
 			errChan <- err
 			return
 		}
+		firstThread.grabInitRegs()
 
 		// Ready to handle requests.
 		errChan <- nil
@@ -179,6 +180,7 @@ func newSubprocess(create func() (*thread, error)) (*subprocess, error) {
 
 			// Detach the thread.
 			t.detach()
+			t.initRegs = firstThread.initRegs
 
 			// Return the thread.
 			r <- t
@@ -269,7 +271,9 @@ func (t *thread) attach() {
 
 	// Initialize options.
 	t.init()
+}
 
+func (t *thread) grabInitRegs() {
 	// Grab registers.
 	//
 	// Note that we adjust the current register RIP value to be just before
diff --git a/pkg/sentry/platform/ptrace/subprocess_linux.go b/pkg/sentry/platform/ptrace/subprocess_linux.go
index 84d4cf0bd..dc3475494 100644
--- a/pkg/sentry/platform/ptrace/subprocess_linux.go
+++ b/pkg/sentry/platform/ptrace/subprocess_linux.go
@@ -235,6 +235,7 @@ func attachedThread(flags uintptr, defaultAction linux.BPFAction) (*thread, erro
 			return nil, fmt.Errorf("wait failed: expected SIGSTOP, got %v", sig)
 		}
 		t.attach()
+		t.grabInitRegs()
 
 		return t, nil
 	}
-- 
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