[PATCH v6 2/9] futex: Make exit_robust_list32() unconditionally available for 64-bit kernels

André Almeida
2025-11-22T05:51:17Z

The new syscall set_robust_list2() needs to handle both 64-bit and
32-bit robust lists, but not every 64-bit platform have compat entry
points. Make exit_robust_list32() unconditionally available for 64-bit
kernels regardless of having a compat configuration.

Signed-off-by: André Almeida <andrealmeid@igalia.com>
---
kernel/futex/core.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index c99d7baab24e..136639897ff9 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -31,7 +31,6 @@
* "The futexes are also cursed."
* "But they come in a choice of three flavours!"
*/
-#include <linux/compat.h>
#include <linux/jhash.h>
#include <linux/pagemap.h>
#include <linux/debugfs.h>
@@ -1213,12 +1212,12 @@ static void exit_robust_list(struct task_struct *curr)
}
}

-#ifdef CONFIG_COMPAT
+#ifdef CONFIG_64BIT
static void __user *futex_uaddr(struct robust_list __user *entry,
compat_long_t futex_offset)
{
- compat_uptr_t base = ptr_to_compat(entry);
- void __user *uaddr = compat_ptr(base + futex_offset);
+ u32 base = (u32)(unsigned long)(entry);
+ void __user *uaddr = (void __user *)(unsigned long)(base + futex_offset);

return uaddr;
}
@@ -1227,13 +1226,13 @@ static void __user *futex_uaddr(struct robust_list __user *entry,
* Fetch a robust-list pointer. Bit 0 signals PI futexes:
*/
static inline int
-fetch_robust_entry32(compat_uptr_t *uentry, struct robust_list __user **entry,
- compat_uptr_t __user *head, unsigned int *pi)
+fetch_robust_entry32(u32 *uentry, struct robust_list __user **entry,
+ u32 __user *head, unsigned int *pi)
{
if (get_user(*uentry, head))
return -EFAULT;

- *entry = compat_ptr((*uentry) & ~1);
+ *entry = (void __user *)(unsigned long)((*uentry) & ~1);
*pi = (unsigned int)(*uentry) & 1;

return 0;
@@ -1251,8 +1250,8 @@ static void exit_robust_list32(struct task_struct *curr)
struct robust_list __user *entry, *next_entry, *pending;
unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
unsigned int next_pi;
- compat_uptr_t uentry, next_uentry, upending;
- compat_long_t futex_offset;
+ u32 uentry, next_uentry, upending;
+ s32 futex_offset;
int rc;

/*
@@ -1412,7 +1411,7 @@ static void futex_cleanup(struct task_struct *tsk)
tsk->robust_list = NULL;
}

-#ifdef CONFIG_COMPAT
+#ifdef CONFIG_64BIT
if (unlikely(tsk->robust_list32)) {
exit_robust_list32(tsk);
tsk->robust_list32 = NULL;

--
2.52.0