Thread (28 messages) 28 messages, 7 authors, 2020-09-22

Re: [PATCH v6 5/9] kernel: Implement selective syscall userspace redirection

flat view

From: peterz@infradead.org
Date: 2020-09-11 09:44:40
Also in: linux-kselftest, lkml 

On Fri, Sep 04, 2020 at 04:31:43PM -0400, Gabriel Krisman Bertazi wrote:
quoted hunk ↗ jump to hunk
+struct syscall_user_dispatch {
+	char __user *selector;
+	unsigned long dispatcher_start;
+	unsigned long dispatcher_end;
+};
quoted hunk ↗ jump to hunk
+int do_syscall_user_dispatch(struct pt_regs *regs)
+{
+	struct syscall_user_dispatch *sd = &current->syscall_dispatch;
+	unsigned long ip = instruction_pointer(regs);
+	char state;
+
+	if (likely(ip >= sd->dispatcher_start && ip <= sd->dispatcher_end))
+		return 0;
If you use {offset,size}, instead of {start,end}, you can write the
above like:

	if (ip - sd->dispatcher_offset < sd->dispatcher_size)
		return 0;

which is just a single branch.

  



    
  

  
    

      

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