Module Name: src
Committed By: riastradh
Date: Wed Mar 5 12:02:00 UTC 2025
Modified Files:
src/sys/kern: sys_futex.c
src/sys/sys: futex.h
src/tests/lib/libc/sys: t_futex_ops.c
Log Message:
futex(2): Sign-extend FUTEX_WAKE_OP oparg/cmparg as Linux does.
Also mask off bits in the FUTEX_OP macro as Linux does so that passing
negative arguments works like in Linux.
PR kern/59129: futex(3): missing sign extension in FUTEX_WAKE_OP
To generate a diff of this commit:
cvs rdiff -u -r1.22 -r1.23 src/sys/kern/sys_futex.c
cvs rdiff -u -r1.6 -r1.7 src/sys/sys/futex.h
cvs rdiff -u -r1.13 -r1.14 src/tests/lib/libc/sys/t_futex_ops.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/sys_futex.c
diff -u src/sys/kern/sys_futex.c:1.22 src/sys/kern/sys_futex.c:1.23
--- src/sys/kern/sys_futex.c:1.22 Sat Jan 18 07:26:21 2025
+++ src/sys/kern/sys_futex.c Wed Mar 5 12:02:00 2025
@@ -1,4 +1,4 @@
-/* $NetBSD: sys_futex.c,v 1.22 2025/01/18 07:26:21 riastradh Exp $ */
+/* $NetBSD: sys_futex.c,v 1.23 2025/03/05 12:02:00 riastradh Exp $ */
/*-
* Copyright (c) 2018, 2019, 2020 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_futex.c,v 1.22 2025/01/18 07:26:21 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_futex.c,v 1.23 2025/03/05 12:02:00 riastradh Exp $");
/*
* Futexes
@@ -1401,6 +1401,22 @@ out:
}
/*
+ * futex_opcmp_arg(arg)
+ *
+ * arg is either the oparg or cmparg field of a FUTEX_WAKE_OP
+ * operation, a 12-bit string in either case. Map it to a numeric
+ * argument value by sign-extending it in two's-complement
+ * representation.
+ */
+static int
+futex_opcmp_arg(int arg)
+{
+
+ KASSERT(arg == (arg & __BITS(11,0)));
+ return arg - 0x1000*__SHIFTOUT(arg, __BIT(11));
+}
+
+/*
* futex_validate_op_cmp(val3)
*
* Validate an op/cmp argument for FUTEX_WAKE_OP.
@@ -1412,7 +1428,8 @@ futex_validate_op_cmp(int val3)
int cmp = __SHIFTOUT(val3, FUTEX_OP_CMP_MASK);
if (op & FUTEX_OP_OPARG_SHIFT) {
- int oparg = __SHIFTOUT(val3, FUTEX_OP_OPARG_MASK);
+ int oparg =
+ futex_opcmp_arg(__SHIFTOUT(val3, FUTEX_OP_OPARG_MASK));
if (oparg < 0)
return EINVAL;
if (oparg >= 32)
@@ -1449,13 +1466,13 @@ futex_validate_op_cmp(int val3)
/*
* futex_compute_op(oldval, val3)
*
- * Apply a FUTEX_WAIT_OP operation to oldval.
+ * Apply a FUTEX_WAKE_OP operation to oldval.
*/
static int
futex_compute_op(int oldval, int val3)
{
int op = __SHIFTOUT(val3, FUTEX_OP_OP_MASK);
- int oparg = __SHIFTOUT(val3, FUTEX_OP_OPARG_MASK);
+ int oparg = futex_opcmp_arg(__SHIFTOUT(val3, FUTEX_OP_OPARG_MASK));
if (op & FUTEX_OP_OPARG_SHIFT) {
KASSERT(oparg >= 0);
@@ -1493,13 +1510,13 @@ futex_compute_op(int oldval, int val3)
/*
* futex_compute_cmp(oldval, val3)
*
- * Apply a FUTEX_WAIT_OP comparison to oldval.
+ * Apply a FUTEX_WAKE_OP comparison to oldval.
*/
static bool
futex_compute_cmp(int oldval, int val3)
{
int cmp = __SHIFTOUT(val3, FUTEX_OP_CMP_MASK);
- int cmparg = __SHIFTOUT(val3, FUTEX_OP_CMPARG_MASK);
+ int cmparg = futex_opcmp_arg(__SHIFTOUT(val3, FUTEX_OP_CMPARG_MASK));
switch (cmp) {
case FUTEX_OP_CMP_EQ:
Index: src/sys/sys/futex.h
diff -u src/sys/sys/futex.h:1.6 src/sys/sys/futex.h:1.7
--- src/sys/sys/futex.h:1.6 Tue Mar 4 12:43:40 2025
+++ src/sys/sys/futex.h Wed Mar 5 12:02:00 2025
@@ -1,4 +1,4 @@
-/* $NetBSD: futex.h,v 1.6 2025/03/04 12:43:40 riastradh Exp $ */
+/* $NetBSD: futex.h,v 1.7 2025/03/05 12:02:00 riastradh Exp $ */
/*-
* Copyright (c) 2018, 2019 The NetBSD Foundation, Inc.
@@ -98,10 +98,10 @@
#define FUTEX_OP_CMPARG_MASK __BITS(0,11)
#define FUTEX_OP(op, oparg, cmp, cmparg) \
- (__SHIFTIN(op, FUTEX_OP_OP_MASK) |\
- __SHIFTIN(oparg, FUTEX_OP_OPARG_MASK) |\
- __SHIFTIN(cmp, FUTEX_OP_CMP_MASK) |\
- __SHIFTIN(cmparg, FUTEX_OP_CMPARG_MASK))
+ (__SHIFTIN((op) & 0xf, FUTEX_OP_OP_MASK) |\
+ __SHIFTIN((oparg) & 0xfff, FUTEX_OP_OPARG_MASK)|\
+ __SHIFTIN((cmp) & 0xf, FUTEX_OP_CMP_MASK) |\
+ __SHIFTIN((cmparg) & 0xfff, FUTEX_OP_CMPARG_MASK))
#define FUTEX_OP_SET 0
#define FUTEX_OP_ADD 1
Index: src/tests/lib/libc/sys/t_futex_ops.c
diff -u src/tests/lib/libc/sys/t_futex_ops.c:1.13 src/tests/lib/libc/sys/t_futex_ops.c:1.14
--- src/tests/lib/libc/sys/t_futex_ops.c:1.13 Wed Mar 5 00:03:12 2025
+++ src/tests/lib/libc/sys/t_futex_ops.c Wed Mar 5 12:02:00 2025
@@ -1,4 +1,4 @@
-/* $NetBSD: t_futex_ops.c,v 1.13 2025/03/05 00:03:12 riastradh Exp $ */
+/* $NetBSD: t_futex_ops.c,v 1.14 2025/03/05 12:02:00 riastradh Exp $ */
/*-
* Copyright (c) 2019, 2020 The NetBSD Foundation, Inc.
@@ -29,7 +29,7 @@
#include <sys/cdefs.h>
__COPYRIGHT("@(#) Copyright (c) 2019, 2020\
The NetBSD Foundation, inc. All rights reserved.");
-__RCSID("$NetBSD: t_futex_ops.c,v 1.13 2025/03/05 00:03:12 riastradh Exp $");
+__RCSID("$NetBSD: t_futex_ops.c,v 1.14 2025/03/05 12:02:00 riastradh Exp $");
#include <sys/fcntl.h>
#include <sys/mman.h>
@@ -1046,8 +1046,6 @@ do_futex_wake_op_op_test(int flags)
/*
* Verify oparg is sign-extended.
*/
- atf_tc_expect_fail("PR kern/59129: futex(3):"
- " missing sign extension in FUTEX_WAKE_OP");
futex_word1 = 0;
op = FUTEX_OP(FUTEX_OP_SET, 0xfff, FUTEX_OP_CMP_EQ, 0);
RL(n = __futex(&futex_word, FUTEX_WAKE_OP | flags,
@@ -1056,7 +1054,7 @@ do_futex_wake_op_op_test(int flags)
ATF_CHECK_EQ_MSG(futex_word1, -1, "futex_word1=%d", futex_word1);
futex_word1 = 0;
- op = (int)FUTEX_OP(FUTEX_OP_SET, -1, FUTEX_OP_CMP_EQ, 0);
+ op = FUTEX_OP(FUTEX_OP_SET, -1, FUTEX_OP_CMP_EQ, 0);
RL(n = __futex(&futex_word, FUTEX_WAKE_OP | flags,
0, NULL, &futex_word1, 0, op));
ATF_CHECK_EQ_MSG(n, 0, "n=%d woken", n);
@@ -1141,8 +1139,6 @@ do_futex_wake_op_cmp_test(int flags)
create_wake_op_test_lwps(flags);
/* #LWPs = 6 */
- atf_tc_expect_fail("PR kern/59129: futex(3):"
- " missing sign extension in FUTEX_WAKE_OP");
futex_word1 = 0xfff;
op = FUTEX_OP(FUTEX_OP_SET, 0, FUTEX_OP_CMP_EQ, 0xfff);
RL(n = __futex(&futex_word, FUTEX_WAKE_OP | flags,
@@ -1151,7 +1147,7 @@ do_futex_wake_op_cmp_test(int flags)
ATF_CHECK_EQ_MSG(futex_word1, 0, "futex_word1=%d", futex_word1);
futex_word1 = 0xfff;
- op = (int)FUTEX_OP(FUTEX_OP_SET, 0, FUTEX_OP_CMP_EQ, -1);
+ op = FUTEX_OP(FUTEX_OP_SET, 0, FUTEX_OP_CMP_EQ, -1);
RL(n = __futex(&futex_word, FUTEX_WAKE_OP | flags,
0, NULL, &futex_word1, 1, op));
ATF_CHECK_EQ_MSG(n, 0, "n=%d woken", n);
