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    SubjectRe: [PATCH v7 3.2-rc2 5/30] uprobes: copy of the original instruction.
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    On Fri, 2011-11-18 at 16:37 +0530, Srikar Dronamraju wrote:
    > +static int __copy_insn(struct address_space *mapping,
    > + struct vm_area_struct *vma, char *insn,
    > + unsigned long nbytes, unsigned long offset)
    > +{
    > + struct file *filp = vma->vm_file;
    > + struct page *page;
    > + void *vaddr;
    > + unsigned long off1;
    > + unsigned long idx;
    > +
    > + if (!filp)
    > + return -EINVAL;
    > +
    > + idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT);
    > + off1 = offset &= ~PAGE_MASK;
    > +
    > + /*
    > + * Ensure that the page that has the original instruction is
    > + * populated and in page-cache.
    > + */
    > + page = read_mapping_page(mapping, idx, filp);
    > + if (IS_ERR(page))
    > + return -ENOMEM;
    > +
    > + vaddr = kmap_atomic(page);
    > + memcpy(insn, vaddr + off1, nbytes);
    > + kunmap_atomic(vaddr);
    > + page_cache_release(page);
    > + return 0;
    > +}
    > +
    > +static int copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma,
    > + unsigned long addr)
    > +{
    > + struct address_space *mapping;
    > + int bytes;
    > + unsigned long nbytes;
    > +
    > + addr &= ~PAGE_MASK;
    > + nbytes = PAGE_SIZE - addr;
    > + mapping = uprobe->inode->i_mapping;
    > +
    > + /* Instruction at end of binary; copy only available bytes */
    > + if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
    > + bytes = uprobe->inode->i_size - uprobe->offset;
    > + else
    > + bytes = MAX_UINSN_BYTES;
    > +
    > + /* Instruction at the page-boundary; copy bytes in second page */
    > + if (nbytes < bytes) {
    > + if (__copy_insn(mapping, vma, uprobe->insn + nbytes,
    > + bytes - nbytes, uprobe->offset + nbytes))
    > + return -ENOMEM;

    You just lost your possible -EINVAL return value.

    > +
    > + bytes = nbytes;
    > + }
    > + return __copy_insn(mapping, vma, uprobe->insn, bytes, uprobe->offset);
    > +}


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