6 files changed, 43 insertions, 12 deletions
diff --git a/libsandbox/trace/linux/arch.c b/libsandbox/trace/linux/arch.c
index de86109..df2fe5b 100644
--- a/libsandbox/trace/linux/arch.c
+++ b/libsandbox/trace/linux/arch.c
@@ -20,4 +20,18 @@
 #ifdef SB_NO_TRACE_ARCH
 # warning "trace: sorry, no support for your architecture"
 # define SB_NO_TRACE
+#else
+# ifdef trace_sysnum_puser
+
+static int trace_sysnum(void)
+{
+	return do_peekuser(trace_sysnum_puser);
+}
+
+static void trace_set_sysnum(void *vregs, long nr)
+{
+	do_pokeuser(trace_sysnum_puser, nr);
+}
+
+# endif
 #endif
diff --git a/libsandbox/trace/linux/bfin.c b/libsandbox/trace/linux/bfin.c
index 4188034..60a8ef8 100644
--- a/libsandbox/trace/linux/bfin.c
+++ b/libsandbox/trace/linux/bfin.c
@@ -1,7 +1,4 @@
-static int trace_sysnum(void)
-{
-	return do_peekuser(PT_ORIG_P0);
-}
+#define trace_sysnum_puser PT_ORIG_P0
 
 static long trace_raw_ret(void *vregs)
 {
@@ -9,6 +6,11 @@ static long trace_raw_ret(void *vregs)
 	return regs->r0;
 }
 
+static void trace_set_ret(void *vregs, int err)
+{
+	do_pokeuser(PT_R0, -err);
+}
+
 static unsigned long trace_arg(void *vregs, int num)
 {
 	trace_regs *regs = vregs;
diff --git a/libsandbox/trace/linux/common.c b/libsandbox/trace/linux/common.c
index 287af0a..de74caf 100644
--- a/libsandbox/trace/linux/common.c
+++ b/libsandbox/trace/linux/common.c
@@ -1,4 +1,5 @@
 static long do_peekuser(long offset);
+static long do_pokeuser(long offset, long val);
 
 static int trace_errno(long err)
 {
diff --git a/libsandbox/trace/linux/hppa.c b/libsandbox/trace/linux/hppa.c
index d98310f..b7fab1c 100644
--- a/libsandbox/trace/linux/hppa.c
+++ b/libsandbox/trace/linux/hppa.c
@@ -1,7 +1,4 @@
-static int trace_sysnum(void)
-{
-	return do_peekuser(20 * 4); /* PT_GR20 */
-}
+#define trace_sysnum_puser (20 * 4)	/* PT_GR20 */
 
 static long trace_raw_ret(void *vregs)
 {
@@ -9,6 +6,11 @@ static long trace_raw_ret(void *vregs)
 	return regs->gr[28];
 }
 
+static void trace_set_ret(void *vregs, int err)
+{
+	do_pokeuser(28 * 4 /* PT_GR28 */, -err);
+}
+
 static unsigned long trace_arg(void *vregs, int num)
 {
 	trace_regs *regs = vregs;
diff --git a/libsandbox/trace/linux/i386.c b/libsandbox/trace/linux/i386.c
index 7508e25..9a3f590 100644
--- a/libsandbox/trace/linux/i386.c
+++ b/libsandbox/trace/linux/i386.c
@@ -1,7 +1,4 @@
-static int trace_sysnum(void)
-{
-	return do_peekuser(4 * ORIG_EAX);
-}
+#define trace_sysnum_puser (4 * ORIG_EAX)
 
 static long trace_raw_ret(void *vregs)
 {
@@ -9,6 +6,11 @@ static long trace_raw_ret(void *vregs)
 	return regs->eax;
 }
 
+static void trace_set_ret(void *vregs, int err)
+{
+	do_pokeuser(EAX, -err);
+}
+
 static unsigned long trace_arg(void *vregs, int num)
 {
 	trace_regs *regs = vregs;
diff --git a/libsandbox/trace/linux/x86_64.c b/libsandbox/trace/linux/x86_64.c
index b864801..0110302 100644
--- a/libsandbox/trace/linux/x86_64.c
+++ b/libsandbox/trace/linux/x86_64.c
@@ -47,6 +47,16 @@ static long trace_raw_ret(void *vregs)
 	return pers_is_32() ? (int)regs->rax : regs->rax;
 }
 
+static void trace_set_sysnum(void *vregs, long nr)
+{
+	do_pokeuser(8 * ORIG_RAX, nr);
+}
+
+static void trace_set_ret(void *vregs, int err)
+{
+	do_pokeuser(8 * RAX, -err);
+}
+
 static unsigned long trace_arg(void *vregs, int num)
 {
 	trace_regs *regs = vregs;