Commit 4b01a53c authored by Eugene Shatokhin's avatar Eugene Shatokhin Committed by Luis Henriques

kprobes/x86: Return correct length in __copy_instruction()

commit c80e5c0c upstream.

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.localdomainSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
[ luis: backported to 3.16: used Eugene's backport for 3.16.y-3.18.y ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 5de41390
......@@ -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)
......
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