uprobes: Teach copy_insn() to support tmpfs
tmpfs is widely used but as Denys reports shmem_aops doesn't have ->readpage() and thus you can't probe a binary on this filesystem. As Hugh suggested we can use shmem_read_mapping_page() in this case, just we need to check shmem_mapping() if ->readpage == NULL. Reported-by: Denys Vlasenko <dvlasenk@redhat.com> Suggested-by: Hugh Dickins <hughd@google.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: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140519184136.GB6750@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -36,6 +36,7 @@
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#include "../../mm/internal.h" /* munlock_vma_page */
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#include <linux/percpu-rwsem.h>
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#include <linux/task_work.h>
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#include <linux/shmem_fs.h>
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#include <linux/uprobes.h>
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@ -537,10 +538,14 @@ static int __copy_insn(struct address_space *mapping, struct file *filp,
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{
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struct page *page;
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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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* Ensure that the page that has the original instruction is populated
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* and in page-cache. If ->readpage == NULL it must be shmem_mapping(),
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* see uprobe_register().
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*/
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page = read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT, filp);
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if (mapping->a_ops->readpage)
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page = read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT, filp);
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else
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page = shmem_read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT);
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if (IS_ERR(page))
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return PTR_ERR(page);
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@ -876,8 +881,8 @@ 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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/* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */
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if (!inode->i_mapping->a_ops->readpage && !shmem_mapping(inode->i_mapping))
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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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