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bpf/error-inject/kprobes: Clear current_kprobe and enable preempt in …
…kprobe Clear current_kprobe and enable preemption in kprobe even if pre_handler returns !0. This simplifies function override using kprobes. Jprobe used to require to keep the preemption disabled and keep current_kprobe until it returned to original function entry. For this reason kprobe_int3_handler() and similar arch dependent kprobe handers checks pre_handler result and exit without enabling preemption if the result is !0. After removing the jprobe, Kprobes does not need to keep preempt disabled even if user handler returns !0 anymore. But since the function override handler in error-inject and bpf is also returns !0 if it overrides a function, to balancing the preempt count, it enables preemption and reset current kprobe by itself. That is a bad design that is very buggy. This fixes such unbalanced preempt-count and current_kprobes setting in kprobes, bpf and error-inject. Note: for powerpc and x86, this removes all preempt_disable from kprobe_ftrace_handler because ftrace callbacks are called under preempt disabled. Signed-off-by: Masami Hiramatsu <[email protected]> Acked-by: Thomas Gleixner <[email protected]> Acked-by: Naveen N. Rao <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Ananth N Mavinakayanahalli <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Benjamin Herrenschmidt <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: David S. Miller <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: Heiko Carstens <[email protected]> Cc: James Hogan <[email protected]> Cc: Josef Bacik <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Martin Schwidefsky <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Ralf Baechle <[email protected]> Cc: Rich Felker <[email protected]> Cc: Russell King <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Tony Luck <[email protected]> Cc: Vineet Gupta <[email protected]> Cc: Will Deacon <[email protected]> Cc: Yoshinori Sato <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: https://lore.kernel.org/lkml/152942494574.15209.12323837825873032258.stgit@devbox Signed-off-by: Ingo Molnar <[email protected]>
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