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uprobes: Change prepare_uretprobe() to (try to) flush the dead frames
Change prepare_uretprobe() to flush the !arch_uretprobe_is_alive() return_instance's. This is not needed correctness-wise, but can help to avoid the failure caused by MAX_URETPROBE_DEPTH. Note: in this case arch_uretprobe_is_alive() can be false positive, the stack can grow after longjmp(). Unfortunately, the kernel can't 100% solve this problem, but see the next patch. Tested-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134023.GA4776@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -1511,6 +1511,16 @@ static unsigned long get_trampoline_vaddr(void)
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return trampoline_vaddr;
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}
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static void cleanup_return_instances(struct uprobe_task *utask, struct pt_regs *regs)
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{
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struct return_instance *ri = utask->return_instances;
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while (ri && !arch_uretprobe_is_alive(ri, regs)) {
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ri = free_ret_instance(ri);
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utask->depth--;
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}
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utask->return_instances = ri;
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}
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static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
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{
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struct return_instance *ri;
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@ -1541,6 +1551,9 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
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if (orig_ret_vaddr == -1)
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goto fail;
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/* drop the entries invalidated by longjmp() */
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cleanup_return_instances(utask, regs);
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/*
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* We don't want to keep trampoline address in stack, rather keep the
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* original return address of first caller thru all the consequent
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