powerpc/kprobes: Update optprobes to use emulate_update_regs()

[Michael Ellerman]

On Fri, 2017-09-15 at 10:08:21 UTC, "Naveen N. Rao" wrote:
> Optprobes depended on an updated regs->nip from analyse_instr() to
> identify the location to branch back from the optprobes trampoline.
> However, since commit 3cdfcbfd32b9d ("powerpc: Change analyse_instr so
> it doesn't modify *regs"), analyse_instr() doesn't update the registers
> anymore.  Due to this, we end up branching back from the optprobes
> trampoline to the same branch into the trampoline resulting in a loop.
> 
> Fix this by calling out to emulate_update_regs() before using the nip.
> Additionally, explicitly compare the return value from analyse_instr()
> to 1, rather than just checking for !0 so as to guard against any
> future changes to analyse_instr() that may result in -1 being returned
> in more scenarios.
> 
> Fixes: 3cdfcbfd32b9d ("powerpc: Change analyse_instr so it doesn't modify *regs")
> Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/8afafa6fba7809c0785018b77c95b1

cheers