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powerpc/jprobes: Validate break handler invocation as being due to a jprobe_return()

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Fix a circa 2005 FIXME by implementing a check to ensure that we
actually got into the jprobe break handler() due to the trap in
jprobe_return().

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao 2017-09-22 14:40:48 +05:30 committed by Michael Ellerman
parent 6baea433bc
commit 3368f5699a
1 changed files with 9 additions and 11 deletions
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20
arch/powerpc/kernel/kprobes.c
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@ -639,24 +639,22 @@ NOKPROBE_SYMBOL(setjmp_pre_handler);
void __used jprobe_return(void)
{
asm volatile("trap" ::: "memory");
asm volatile("jprobe_return_trap:\n"
"trap\n"
::: "memory");
}
NOKPROBE_SYMBOL(jprobe_return);
static void __used jprobe_return_end(void)
{
}
NOKPROBE_SYMBOL(jprobe_return_end);
int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
/*
* FIXME - we should ideally be validating that we got here 'cos
* of the "trap" in jprobe_return() above, before restoring the
* saved regs...
*/
if (regs->nip != ppc_kallsyms_lookup_name("jprobe_return_trap")) {
pr_debug("longjmp_break_handler NIP (0x%lx) does not match jprobe_return_trap (0x%lx)\n",
regs->nip, ppc_kallsyms_lookup_name("jprobe_return_trap"));
return 0;
}
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
/* It's OK to start function graph tracing again */
unpause_graph_tracing();