Commit c90a6950 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/x86: Simplify riprel_{pre,post}_xol() and make them similar 



Ignoring the "correction" logic riprel_pre_xol() and riprel_post_xol()
are very similar but look quite differently.

1. Add the "UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX" check at the start
   of riprel_pre_xol(), like the same check in riprel_post_xol().

2. Add the trivial scratch_reg() helper which returns the address of
   scratch register pre_xol/post_xol need to change.

3. Change these functions to use the new helper and avoid copy-and-paste
   under if/else branches.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent 7f55e82b

arch/x86/kernel/uprobes.c

+14 −16
Original line number Diff line number Diff line
@@ -326,22 +326,24 @@ static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn) 
	}

}



static inline unsigned long *

scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)

{

	return (auprobe->def.fixups & UPROBE_FIX_RIP_AX) ? &regs->ax : &regs->cx;

}



/*

 * If we're emulating a rip-relative instruction, save the contents

 * of the scratch register and store the target address in that register.

 */

static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)

{

	if (auprobe->def.fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) {

		struct uprobe_task *utask = current->utask;

		unsigned long *sr = scratch_reg(auprobe, regs);



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

		utask->autask.saved_scratch_register = regs->ax;

		regs->ax = utask->vaddr;

		regs->ax += auprobe->def.riprel_target;

	} else if (auprobe->def.fixups & UPROBE_FIX_RIP_CX) {

		utask->autask.saved_scratch_register = regs->cx;

		regs->cx = utask->vaddr;

		regs->cx += auprobe->def.riprel_target;

		utask->autask.saved_scratch_register = *sr;

		*sr = utask->vaddr + auprobe->def.riprel_target;

	}

}
@@ -349,14 +351,10 @@ static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, 
				long *correction)

{

	if (auprobe->def.fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) {

		struct arch_uprobe_task *autask;



		autask = &current->utask->autask;

		if (auprobe->def.fixups & UPROBE_FIX_RIP_AX)

			regs->ax = autask->saved_scratch_register;

		else

			regs->cx = autask->saved_scratch_register;

		struct uprobe_task *utask = current->utask;

		unsigned long *sr = scratch_reg(auprobe, regs);



		*sr = utask->autask.saved_scratch_register;

		/*

		 * The original instruction includes a displacement, and so

		 * is 4 bytes longer than what we've just single-stepped.

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