tree 0dec69ce1815755aec7d8cd7f4c1cdd33226b37f
parent a4979a7e71eb8da976cbe4a0a1fa50636e76b04f
author Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> 1496314097 +0530
committer Michael Ellerman <mpe@ellerman.id.au> 1497606583 +1000

powerpc/kprobes: Skip livepatch_handler() for jprobes

ftrace_caller() depends on a modified regs->nip to detect if a certain
function has been livepatched. However, with KPROBES_ON_FTRACE, it is
possible for regs->nip to have been modified by the kprobes pre_handler
(jprobes, for instance). In this case, we do not want to invoke the
livepatch_handler so as not to consume the livepatch stack.

To distinguish between the two (kprobes and livepatch), we check if
there is an active kprobe on the current function. If there is, then we
know for sure that it must have modified the NIP as we don't support
livepatching a kprobe'd function. In this case, we simply skip the
livepatch_handler and branch to the new NIP. Otherwise, the
livepatch_handler is invoked.

Fixes: ead514d5fb30 ("powerpc/kprobes: Add support for KPROBES_ON_FTRACE")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>