bpf: add a bpf_override_function helper
Error injection is sloppy and very ad-hoc. BPF could fill this niche perfectly with it's kprobe functionality. We could make sure errors are only triggered in specific call chains that we care about with very specific situations. Accomplish this with the bpf_override_funciton helper. This will modify the probe'd callers return value to the specified value and set the PC to an override function that simply returns, bypassing the originally probed function. This gives us a nice clean way to implement systematic error injection for all of our code paths. Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Alexei Starovoitov

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@@ -67,6 +67,10 @@ extern const int kretprobe_blacklist_size;
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void arch_remove_kprobe(struct kprobe *p);
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asmlinkage void kretprobe_trampoline(void);
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#ifdef CONFIG_KPROBES_ON_FTRACE
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extern void arch_ftrace_kprobe_override_function(struct pt_regs *regs);
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#endif
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/* Architecture specific copy of original instruction*/
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struct arch_specific_insn {
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/* copy of the original instruction */
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