[RFC PATCH 05/13] futex2: Add compatibility entry point for x86_x32 ABI

From: André Almeida
Date: Mon Feb 15 2021 - 10:31:14 EST


New syscalls should use the same entry point for x86_64 and x86_x32
paths. Add a wrapper for x32 calls to use parse functions that assumes
32bit pointers.

Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxxxxx>
---
kernel/futex2.c | 42 +++++++++++++++++++++++++++++++++++-------
1 file changed, 35 insertions(+), 7 deletions(-)

diff --git a/kernel/futex2.c b/kernel/futex2.c
index bad8c183cf9f..8a8b45f98d3b 100644
--- a/kernel/futex2.c
+++ b/kernel/futex2.c
@@ -23,6 +23,10 @@
#include <linux/syscalls.h>
#include <uapi/linux/futex.h>

+#ifdef CONFIG_X86_64
+#include <linux/compat.h>
+#endif
+
/**
* struct futex_key - Components to build unique key for a futex
* @pointer: Pointer to current->mm or inode's UUID for file backed futexes
@@ -875,7 +879,16 @@ SYSCALL_DEFINE4(futex_waitv, struct futex_waitv __user *, waiters,
futexv->hint = false;
futexv->task = current;

- ret = futex_parse_waitv(futexv, waiters, nr_futexes);
+#ifdef CONFIG_X86_X32_ABI
+ if (in_x32_syscall()) {
+ ret = compat_futex_parse_waitv(futexv, (struct compat_futex_waitv *)waiters,
+ nr_futexes);
+ } else
+#endif
+ {
+ ret = futex_parse_waitv(futexv, waiters, nr_futexes);
+ }
+
if (!ret)
ret = futex_set_timer_and_wait(futexv, nr_futexes, timo, flags);

@@ -1181,13 +1194,28 @@ SYSCALL_DEFINE6(futex_requeue, struct futex_requeue __user *, uaddr1,
if (flags)
return -EINVAL;

- ret = futex_parse_requeue(&rq1, uaddr1, &shared1);
- if (ret)
- return ret;
+#ifdef CONFIG_X86_X32_ABI
+ if (in_x32_syscall()) {
+ ret = compat_futex_parse_requeue(&rq1, (struct compat_futex_requeue *)uaddr1,
+ &shared1);
+ if (ret)
+ return ret;

- ret = futex_parse_requeue(&rq2, uaddr2, &shared2);
- if (ret)
- return ret;
+ ret = compat_futex_parse_requeue(&rq2, (struct compat_futex_requeue *)uaddr2,
+ &shared2);
+ if (ret)
+ return ret;
+ } else
+#endif
+ {
+ ret = futex_parse_requeue(&rq1, uaddr1, &shared1);
+ if (ret)
+ return ret;
+
+ ret = futex_parse_requeue(&rq2, uaddr2, &shared2);
+ if (ret)
+ return ret;
+ }

return __futex_requeue(rq1, rq2, nr_wake, nr_requeue, cmpval, shared1, shared2);
}
--
2.30.1