projects/linux·commit 1d17e808

Merge tag 'core-rseq-2025-09-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

1d17e808 · Linus Torvalds <[email protected]> · 2025-09-30 15:06:33 -07:00

Pull rseq updates from Thomas Gleixner:
 "Two fixes for RSEQ:

   - Protect the event mask modification against the membarrier() IPI as
     otherwise the RmW operation is unprotected and events might be lost

   - Fix the weak symbol reference in rseq selftests

     The current weak RSEQ symbols definitions which were added to allow
     static linkage are not working correctly as they effectively
     re-define the glibc symbols leading to multiple versions of the
     symbols when compiled with -fno-common.

     Mark them as 'extern' to convert them from weak symbol definitions
     to weak symbol references. That works with static and dynamic
     linkage independent of -fcommon and -fno-common"

* tag 'core-rseq-2025-09-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rseq/selftests: Use weak symbol reference, not definition, to link with glibc
  rseq: Protect event mask against membarrier IPI
Commit
1d17e808cf2aad182f0eb2ea83e329e4a6795428
Parents
7601d18b · a001cd24

Merge commit. Changes below are compared with the first parent: 7601d18b.

Changes

3 files changed · +17 −12

FileStatusAddDelContent
include/linux/rseq.hmodified+8−3View file
kernel/rseq.cmodified+5−5View file
tools/testing/selftests/rseq/rseq.cmodified+4−4View file

include/linux/rseq.h

View file
diff --git a/include/linux/rseq.h b/include/linux/rseq.h
index a96fd34..69553e7 100644
--- a/include/linux/rseq.h
+++ b/include/linux/rseq.h
@@ -7,6 +7,12 @@
#include <linux/preempt.h>
#include <linux/sched.h>
+#ifdef CONFIG_MEMBARRIER
+# define RSEQ_EVENT_GUARD irq
+#else
+# define RSEQ_EVENT_GUARD preempt
+#endif
+
/*
* Map the event mask on the user-space ABI enum rseq_cs_flags
* for direct mask checks.
@@ -41,9 +47,8 @@ static inline void rseq_handle_notify_resume(struct ksignal *ksig,
static inline void rseq_signal_deliver(struct ksignal *ksig,
struct pt_regs *regs)
{
- preempt_disable();
- __set_bit(RSEQ_EVENT_SIGNAL_BIT, &current->rseq_event_mask);
- preempt_enable();
+ scoped_guard(RSEQ_EVENT_GUARD)
+ __set_bit(RSEQ_EVENT_SIGNAL_BIT, &current->rseq_event_mask);
rseq_handle_notify_resume(ksig, regs);
}

kernel/rseq.c

View file
diff --git a/kernel/rseq.c b/kernel/rseq.c
index b7a1ec3..2452b73 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -342,12 +342,12 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
/*
* Load and clear event mask atomically with respect to
- * scheduler preemption.
+ * scheduler preemption and membarrier IPIs.
*/
- preempt_disable();
- event_mask = t->rseq_event_mask;
- t->rseq_event_mask = 0;
- preempt_enable();
+ scoped_guard(RSEQ_EVENT_GUARD) {
+ event_mask = t->rseq_event_mask;
+ t->rseq_event_mask = 0;
+ }
return !!event_mask;
}

tools/testing/selftests/rseq/rseq.c

View file
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index 663a9ce..dcac5cb 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -40,9 +40,9 @@
* Define weak versions to play nice with binaries that are statically linked
* against a libc that doesn't support registering its own rseq.
*/
-__weak ptrdiff_t __rseq_offset;
-__weak unsigned int __rseq_size;
-__weak unsigned int __rseq_flags;
+extern __weak ptrdiff_t __rseq_offset;
+extern __weak unsigned int __rseq_size;
+extern __weak unsigned int __rseq_flags;
static const ptrdiff_t *libc_rseq_offset_p = &__rseq_offset;
static const unsigned int *libc_rseq_size_p = &__rseq_size;
@@ -209,7 +209,7 @@ void rseq_init(void)
* libc not having registered a restartable sequence. Try to find the
* symbols if that's the case.
*/
- if (!*libc_rseq_size_p) {
+ if (!libc_rseq_size_p || !*libc_rseq_size_p) {
libc_rseq_offset_p = dlsym(RTLD_NEXT, "__rseq_offset");
libc_rseq_size_p = dlsym(RTLD_NEXT, "__rseq_size");
libc_rseq_flags_p = dlsym(RTLD_NEXT, "__rseq_flags");