Commit b7f25a6e authored Mar 17, 2015 by Eugene Shatokhin Committed by Sasha Levin Jul 12, 2015

kprobes/x86: Return correct length in __copy_instruction()



[ Upstream commit c80e5c0c23ce2282476fdc64c4b5e3d3a40723fd ]

On x86-64, __copy_instruction() always returns 0 (error) if the
instruction uses %rip-relative addressing. This is because
kernel_insn_init() is called the second time for 'insn' instance
in such cases and sets all its fields to 0.

Because of this, trying to place a kprobe on such instruction
will fail, register_kprobe() will return -EINVAL.

This patch fixes the problem.

Signed-off-by: Eugene Shatokhin <eugene.shatokhin@rosalab.ru>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/20150317100918.28349.94654.stgit@localhost.localdomain


Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

parent 1551f2cd

arch/x86/kernel/kprobes/core.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -330,13 +330,16 @@ int __copy_instruction(u8 dest, u8 src)
		{
		struct insn insn;
		kprobe_opcode_t buf[MAX_INSN_SIZE];
		int length;

		kernel_insn_init(&insn, (void *)recover_probed_instruction(buf, (unsigned long)src));
		insn_get_length(&insn);
		length = insn.length;

		/* Another subsystem puts a breakpoint, failed to recover */
		if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
		return 0;
		memcpy(dest, insn.kaddr, insn.length);
		memcpy(dest, insn.kaddr, length);

		#ifdef CONFIG_X86_64
		if (insn_rip_relative(&insn)) {
		@@ -366,7 +369,7 @@ int __copy_instruction(u8 dest, u8 src)
		(s32 ) disp = (s32) newdisp;
		}
		#endif
		return insn.length;
		return length;
		}

		static int arch_copy_kprobe(struct kprobe *p)