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Commit c80e5c0c authored by Eugene Shatokhin's avatar Eugene Shatokhin Committed by Ingo Molnar
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kprobes/x86: Return correct length in __copy_instruction() 



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


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 107eb964

arch/x86/kernel/kprobes/core.c

+6 −3
Original line number Original line Diff line number Diff line
@@ -354,6 +354,7 @@ int __copy_instruction(u8 *dest, u8 *src) 
{

{

	struct insn insn;

	struct insn insn;

	kprobe_opcode_t buf[MAX_INSN_SIZE];

	kprobe_opcode_t buf[MAX_INSN_SIZE];

	int length;

	unsigned long recovered_insn =

	unsigned long recovered_insn =

		recover_probed_instruction(buf, (unsigned long)src);

		recover_probed_instruction(buf, (unsigned long)src);
@@ -361,16 +362,18 @@ int __copy_instruction(u8 *dest, u8 *src) 
		return 0;

		return 0;

	kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);

	kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);

	insn_get_length(&insn);

	insn_get_length(&insn);

	length = insn.length;



	/* Another subsystem puts a breakpoint, failed to recover */

	/* Another subsystem puts a breakpoint, failed to recover */

	if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)

	if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)

		return 0;

		return 0;

	memcpy(dest, insn.kaddr, insn.length);

	memcpy(dest, insn.kaddr, length);





#ifdef CONFIG_X86_64

#ifdef CONFIG_X86_64

	if (insn_rip_relative(&insn)) {

	if (insn_rip_relative(&insn)) {

		s64 newdisp;

		s64 newdisp;

		u8 *disp;

		u8 *disp;

		kernel_insn_init(&insn, dest, insn.length);

		kernel_insn_init(&insn, dest, length);

		insn_get_displacement(&insn);

		insn_get_displacement(&insn);

		/*

		/*

		 * The copied instruction uses the %rip-relative addressing

		 * The copied instruction uses the %rip-relative addressing
@@ -394,7 +397,7 @@ int __copy_instruction(u8 *dest, u8 *src) 
		*(s32 *) disp = (s32) newdisp;

		*(s32 *) disp = (s32) newdisp;

	}

	}

#endif

#endif

	return insn.length;

	return length;

}

}





static int arch_copy_kprobe(struct kprobe *p)

static int arch_copy_kprobe(struct kprobe *p)