uprobes: Shift ->readpage check from __copy_insn() to uprobe_register()
copy_insn() fails with -EIO if ->readpage == NULL, but this error is not propagated unless uprobe_register() path finds ->mm which already mmaps this file. In this case (say) "perf record" does not actually install the probe, but the user can't know about this. Move this check into uprobe_register() so that this problem can be detected earlier and reported to user. Note: this is still not perfect, - copy_insn() and arch_uprobe_analyze_insn() should be called by uprobe_register() but this is not simple, we need vm_file for read_mapping_page() (although perhaps we can pass NULL), and we need ->mm for is_64bit_mm() (although this logic is broken anyway). - uprobe_register() should be called by create_trace_uprobe(), not by probe_event_enable(), so that an error can be detected at "perf probe -x" time. This also needs more changes in the core uprobe code, uprobe register/unregister interface was poorly designed from the very beginning. Reported-by: Denys Vlasenko <dvlasenk@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Hugh Dickins <hughd@google.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140519184054.GA6750@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -536,9 +536,6 @@ static int __copy_insn(struct address_space *mapping, struct file *filp,
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void *insn, int nbytes, loff_t offset)
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{
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struct page *page;
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if (!mapping->a_ops->readpage)
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return -EIO;
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/*
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* Ensure that the page that has the original instruction is
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* populated and in page-cache.
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@ -879,6 +876,9 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
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if (!uc->handler && !uc->ret_handler)
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return -EINVAL;
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/* copy_insn()->read_mapping_page() needs ->readpage() */
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if (!inode->i_mapping->a_ops->readpage)
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return -EIO;
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/* Racy, just to catch the obvious mistakes */
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if (offset > i_size_read(inode))
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return -EINVAL;
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