From aae57ac37a8803cdd39a732491718b6ee772bb3d Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@bsdimp.com>
Date: Sat, 8 Jan 2022 17:55:56 -0700
Subject: [PATCH] bsd-user/signal.c: Implement rewind_if_in_safe_syscall

Signed-off-by: Kyle Evans <kevans@freebsd.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 bsd-user/qemu.h   |  2 ++
 bsd-user/signal.c | 13 ++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/bsd-user/qemu.h b/bsd-user/qemu.h
index 49f01932a5..8ed1bfbca8 100644
--- a/bsd-user/qemu.h
+++ b/bsd-user/qemu.h
@@ -446,4 +446,6 @@ static inline void *lock_user_string(abi_ulong guest_addr)
 
 #include <pthread.h>
 
+#include "user/safe-syscall.h"
+
 #endif /* QEMU_H */
diff --git a/bsd-user/signal.c b/bsd-user/signal.c
index db8cf0a08f..454aef2993 100644
--- a/bsd-user/signal.c
+++ b/bsd-user/signal.c
@@ -48,6 +48,18 @@ int target_to_host_signal(int sig)
     return sig;
 }
 
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+    ucontext_t *uc = (ucontext_t *)puc;
+    uintptr_t pcreg = host_signal_pc(uc);
+
+    if (pcreg > (uintptr_t)safe_syscall_start
+        && pcreg < (uintptr_t)safe_syscall_end) {
+        host_signal_set_pc(uc, (uintptr_t)safe_syscall_start);
+    }
+}
+
 static bool has_trapno(int tsig)
 {
     return tsig == TARGET_SIGILL ||
@@ -57,7 +69,6 @@ static bool has_trapno(int tsig)
         tsig == TARGET_SIGTRAP;
 }
 
-
 /* Siginfo conversion. */
 
 /*