arm: kprobes: Make space for instruction pointer on stack

Since arm's __kretprobe_trampoline() saves partial 'pt_regs' on the
stack, 'regs->ARM_pc' (instruction pointer) is not accessible from
the kretprobe handler. This means if instruction_pointer_set() is
used from kretprobe handler, it will break the data on the stack.

Make space for instruction pointer (ARM_pc) on the stack in the
__kretprobe_trampoline() for fixing this problem.

Link: https://lkml.kernel.org/r/163163052262.489837.10327621053231461255.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index 67ce7eb..95f23b4 100644 (file)
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -376,11 +376,13 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 void __naked __kprobes __kretprobe_trampoline(void)
 {
        __asm__ __volatile__ (
+               "sub    sp, sp, #16             \n\t"
                "stmdb  sp!, {r0 - r11}         \n\t"
                "mov    r0, sp                  \n\t"
                "bl     trampoline_handler      \n\t"
                "mov    lr, r0                  \n\t"
                "ldmia  sp!, {r0 - r11}         \n\t"
+               "add    sp, sp, #16             \n\t"
 #ifdef CONFIG_THUMB2_KERNEL
                "bx     lr                      \n\t"
 #else