[patch V4 20/36] rseq: Replace the original debug implementation

Thomas Gleixner
2025-09-08T21:32:08Z

Just utilize the new infrastructure and put the original one to rest.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

---
kernel/rseq.c | 80 ++++++++--------------------------------------------------
1 file changed, 12 insertions(+), 68 deletions(-)

--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -472,83 +472,27 @@ void __rseq_handle_notify_resume(struct

#ifdef CONFIG_DEBUG_RSEQ
/*
- * Unsigned comparison will be true when ip >= start_ip, and when
- * ip < start_ip + post_commit_offset.
- */
-static bool in_rseq_cs(unsigned long ip, struct rseq_cs *rseq_cs)
-{
- return ip - rseq_cs->start_ip < rseq_cs->post_commit_offset;
-}
-
-/*
- * If the rseq_cs field of 'struct rseq' contains a valid pointer to
- * user-space, copy 'struct rseq_cs' from user-space and validate its fields.
- */
-static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
-{
- struct rseq_cs __user *urseq_cs;
- u64 ptr;
- u32 __user *usig;
- u32 sig;
- int ret;
-
- if (get_user_masked_u64(&ptr, &t->rseq.usrptr->rseq_cs))
- return -EFAULT;
-
- /* If the rseq_cs pointer is NULL, return a cleared struct rseq_cs. */
- if (!ptr) {
- memset(rseq_cs, 0, sizeof(*rseq_cs));
- return 0;
- }
- /* Check that the pointer value fits in the user-space process space. */
- if (ptr >= TASK_SIZE)
- return -EINVAL;
- urseq_cs = (struct rseq_cs __user *)(unsigned long)ptr;
- if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs)))
- return -EFAULT;
-
- if (rseq_cs->start_ip >= TASK_SIZE ||
- rseq_cs->start_ip + rseq_cs->post_commit_offset >= TASK_SIZE ||
- rseq_cs->abort_ip >= TASK_SIZE ||
- rseq_cs->version > 0)
- return -EINVAL;
- /* Check for overflow. */
- if (rseq_cs->start_ip + rseq_cs->post_commit_offset < rseq_cs->start_ip)
- return -EINVAL;
- /* Ensure that abort_ip is not in the critical section. */
- if (rseq_cs->abort_ip - rseq_cs->start_ip < rseq_cs->post_commit_offset)
- return -EINVAL;
-
- usig = (u32 __user *)(unsigned long)(rseq_cs->abort_ip - sizeof(u32));
- ret = get_user(sig, usig);
- if (ret)
- return ret;
-
- if (current->rseq.sig != sig) {
- printk_ratelimited(KERN_WARNING
- "Possible attack attempt. Unexpected rseq signature 0x%x, expecting 0x%x (pid=%d, addr=%p).\n",
- sig, current->rseq.sig, current->pid, usig);
- return -EINVAL;
- }
- return 0;
-}
-
-/*
* Terminate the process if a syscall is issued within a restartable
* sequence.
*/
void rseq_syscall(struct pt_regs *regs)
{
- unsigned long ip = instruction_pointer(regs);
struct task_struct *t = current;
- struct rseq_cs rseq_cs;
+ u64 csaddr;

- if (!t->rseq.usrptr)
+ if (!t->rseq.event.has_rseq)
+ return;
+ if (get_user_masked_u64(&csaddr, &t->rseq.usrptr->rseq_cs))
+ goto fail;
+ if (likely(!csaddr))
return;
- if (rseq_get_rseq_cs(t, &rseq_cs) || in_rseq_cs(ip, &rseq_cs))
- force_sig(SIGSEGV);
+ if (unlikely(csaddr >= TASK_SIZE))
+ goto fail;
+ if (rseq_debug_update_user_cs(t, regs, csaddr))
+ return;
+fail:
+ force_sig(SIGSEGV);
}
-
#endif

/*