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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: 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>
This commit is contained in:
Eugene Shatokhin 2015-03-17 19:09:18 +09:00 committed by Ingo Molnar
parent 107eb964d8
commit c80e5c0c23
1 changed files with 6 additions and 3 deletions
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9
arch/x86/kernel/kprobes/core.c
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@ -354,6 +354,7 @@ int __copy_instruction(u8 *dest, u8 *src)
{
struct insn insn;
kprobe_opcode_t buf[MAX_INSN_SIZE];
int length;
unsigned long recovered_insn =
recover_probed_instruction(buf, (unsigned long)src);
@ -361,16 +362,18 @@ int __copy_instruction(u8 *dest, u8 *src)
return 0;
kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
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)) {
s64 newdisp;
u8 *disp;
kernel_insn_init(&insn, dest, insn.length);
kernel_insn_init(&insn, dest, length);
insn_get_displacement(&insn);
/*
* The copied instruction uses the %rip-relative addressing
@ -394,7 +397,7 @@ 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)