ptrace: Provide set/get interface for syscall user dispatch

The syscall user dispatch configuration can only be set by the task itself,
but lacks a ptrace set/get interface which makes it impossible to implement
checkpoint/restore for it.

Add the required ptrace requests and the get/set functions in the syscall
user dispatch code to make that possible.

Signed-off-by: Gregory Price <gregory.price@memverge.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20230407171834.3558-4-gregory.price@memverge.com

2 files changed, 48 insertions, 0 deletions

diff --git a/include/linux/syscall_user_dispatch.h b/include/linux/syscall_user_dispatch.h
index a0ae443fb7df..641ca8880995 100644
--- a/include/linux/syscall_user_dispatch.h
+++ b/include/linux/syscall_user_dispatch.h
@@ -22,6 +22,12 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
 #define clear_syscall_work_syscall_user_dispatch(tsk) \
 	clear_task_syscall_work(tsk, SYSCALL_USER_DISPATCH)
 
+int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
+				     void __user *data);
+
+int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
+				     void __user *data);
+
 #else
 struct syscall_user_dispatch {};
 
@@ -35,6 +41,18 @@ static inline void clear_syscall_work_syscall_user_dispatch(struct task_struct *
 {
 }
 
+static inline int syscall_user_dispatch_get_config(struct task_struct *task,
+						   unsigned long size, void __user *data)
+{
+	return -EINVAL;
+}
+
+static inline int syscall_user_dispatch_set_config(struct task_struct *task,
+						   unsigned long size, void __user *data)
+{
+	return -EINVAL;
+}
+
 #endif /* CONFIG_GENERIC_ENTRY */
 
 #endif /* _SYSCALL_USER_DISPATCH_H */
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index 195ae64a8c87..72c038fc71d0 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -112,6 +112,36 @@ struct ptrace_rseq_configuration {
 	__u32 pad;
 };
 
+#define PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG 0x4210
+#define PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG 0x4211
+
+/*
+ * struct ptrace_sud_config - Per-task configuration for Syscall User Dispatch
+ * @mode:	One of PR_SYS_DISPATCH_ON or PR_SYS_DISPATCH_OFF
+ * @selector:	Tracees user virtual address of SUD selector
+ * @offset:	SUD exclusion area (virtual address)
+ * @len:	Length of SUD exclusion area
+ *
+ * Used to get/set the syscall user dispatch configuration for a tracee.
+ * Selector is optional (may be NULL), and if invalid will produce
+ * a SIGSEGV in the tracee upon first access.
+ *
+ * If mode is PR_SYS_DISPATCH_ON, syscall dispatch will be enabled. If
+ * PR_SYS_DISPATCH_OFF, syscall dispatch will be disabled and all other
+ * parameters must be 0.  The value in *selector (if not null), also determines
+ * whether syscall dispatch will occur.
+ *
+ * The Syscall User Dispatch Exclusion area described by offset/len is the
+ * virtual address space from which syscalls will not produce a user
+ * dispatch.
+ */
+struct ptrace_sud_config {
+	__u64 mode;
+	__u64 selector;
+	__u64 offset;
+	__u64 len;
+};
+
 /*
  * These values are stored in task->ptrace_message
  * by ptrace_stop to describe the current syscall-stop.