Commit 1dc76e6e authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/x86: Kill adjust_ret_addr(), simplify UPROBE_FIX_CALL logic 



The only insn which could have both UPROBE_FIX_IP and UPROBE_FIX_CALL
was 0xe8 "call relative", and now it is handled by branch_xol_ops.

So we can change default_post_xol_op(UPROBE_FIX_CALL) to simply push
the address of next insn == utask->vaddr + insn.length, just we need
to record insn.length into the new auprobe->def.ilen member.

Note: if/when we teach branch_xol_ops to support jcxz/loopz we can
remove the "correction" logic, UPROBE_FIX_IP can use the same address.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
parent 2b82cadf

arch/x86/include/asm/uprobes.h

+1 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ struct arch_uprobe { 
			long	riprel_target;

#endif

			u8	fixups;

			u8	ilen;

		} 			def;

	};

};

arch/x86/kernel/uprobes.c

+3 −21
Original line number Diff line number Diff line
@@ -418,24 +418,6 @@ static int push_ret_address(struct pt_regs *regs, unsigned long ip) 
	return 0;

}



/*

 * Adjust the return address pushed by a call insn executed out of line.

 */

static int adjust_ret_addr(unsigned long sp, long correction)

{

	int rasize = sizeof_long();

	long ra;



	if (copy_from_user(&ra, (void __user *)sp, rasize))

		return -EFAULT;



	ra += correction;

	if (copy_to_user((void __user *)sp, &ra, rasize))

		return -EFAULT;



	return 0;

}



static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)

{

	struct uprobe_task *utask = current->utask;
@@ -446,11 +428,10 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs 
		regs->ip += correction;



	if (auprobe->def.fixups & UPROBE_FIX_CALL) {

		if (adjust_ret_addr(regs->sp, correction)) {

		regs->sp += sizeof_long();

		if (push_ret_address(regs, utask->vaddr + auprobe->def.ilen))

			return -ERESTART;

	}

	}

	/* popf; tell the caller to not touch TF */

	if (auprobe->def.fixups & UPROBE_FIX_SETF)

		utask->autask.saved_tf = true;
@@ -687,6 +668,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, 
		handle_riprel_insn(auprobe, &insn);

	}



	auprobe->def.ilen = insn.length;

	if (fix_ip)

		auprobe->def.fixups |= UPROBE_FIX_IP;

	if (fix_call)

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