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powerpc/kprobes: Pause function_graph tracing during jprobes handling 

This fixes a crash when function_graph and jprobes are used together.
This is essentially commit 237d28db03 ("ftrace/jprobes/x86: Fix
conflict between jprobes and function graph tracing"), but for powerpc.

Jprobes breaks function_graph tracing since the jprobe hook needs to use
jprobe_return(), which never returns back to the hook, but instead to
the original jprobe'd function. The solution is to momentarily pause
function_graph tracing before invoking the jprobe hook and re-enable it
when returning back to the original jprobe'd function.

Fixes: 6794c78243 ("powerpc64: port of the function graph tracer")
Cc: stable@vger.kernel.org # v2.6.30+
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao 2017-06-01 16:18:15 +05:30 committed by Michael Ellerman
parent a093c92dc7
commit a9f8553e93
1 changed files with 11 additions and 0 deletions
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11
arch/powerpc/kernel/kprobes.c
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@ -617,6 +617,15 @@ int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc); regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
#endif #endif
/*
* jprobes use jprobe_return() which skips the normal return
* path of the function, and this messes up the accounting of the
* function graph tracer.
*
* Pause function graph tracing while performing the jprobe function.
*/
pause_graph_tracing();
return 1; return 1;
} }
NOKPROBE_SYMBOL(setjmp_pre_handler); NOKPROBE_SYMBOL(setjmp_pre_handler);
@ -642,6 +651,8 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
* saved regs... * saved regs...
*/ */
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs)); memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
/* It's OK to start function graph tracing again */
unpause_graph_tracing();
preempt_enable_no_resched(); preempt_enable_no_resched();
return 1; return 1;
} }