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uprobes: Change handle_trampoline() to find the next chain beforehand
No functional changes, preparation. Add the new helper, find_next_ret_chain(), which finds the first !chained entry and returns its ->next. Yes, it is suboptimal. We probably want to turn ->chained into ->start_of_this_chain pointer and avoid another loop. But this needs the boring changes in dup_utask(), so lets do this later. Change the main loop in handle_trampoline() to unwind the stack until ri is equal to the pointer returned by this new helper. 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/20150721134013.GA4755@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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1 changed files with 16 additions and 11 deletions
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@ -1766,11 +1766,22 @@ handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
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up_read(&uprobe->register_rwsem);
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}
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static struct return_instance *find_next_ret_chain(struct return_instance *ri)
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{
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bool chained;
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do {
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chained = ri->chained;
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ri = ri->next; /* can't be NULL if chained */
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} while (chained);
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return ri;
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}
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static void handle_trampoline(struct pt_regs *regs)
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{
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struct uprobe_task *utask;
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struct return_instance *ri;
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bool chained;
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struct return_instance *ri, *next;
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utask = current->utask;
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if (!utask)
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@ -1780,24 +1791,18 @@ static void handle_trampoline(struct pt_regs *regs)
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if (!ri)
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goto sigill;
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next = find_next_ret_chain(ri);
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/*
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* TODO: we should throw out return_instance's invalidated by
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* longjmp(), currently we assume that the probed function always
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* returns.
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*/
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instruction_pointer_set(regs, ri->orig_ret_vaddr);
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for (;;) {
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do {
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handle_uretprobe_chain(ri, regs);
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chained = ri->chained;
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ri = free_ret_instance(ri);
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utask->depth--;
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if (!chained)
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break;
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BUG_ON(!ri);
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}
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} while (ri != next);
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utask->return_instances = ri;
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return;
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