cregit-Linux how code gets into the kernel

Release 4.15 net/rds/info.c

Directory: net/rds
/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/percpu.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/export.h>

#include "rds.h"

/*
 * This file implements a getsockopt() call which copies a set of fixed
 * sized structs into a user-specified buffer as a means of providing
 * read-only information about RDS.
 *
 * For a given information source there are a given number of fixed sized
 * structs at a given time.  The structs are only copied if the user-specified
 * buffer is big enough.  The destination pages that make up the buffer
 * are pinned for the duration of the copy.
 *
 * This gives us the following benefits:
 *
 * - simple implementation, no copy "position" across multiple calls
 * - consistent snapshot of an info source
 * - atomic copy works well with whatever locking info source has
 * - one portable tool to get rds info across implementations
 * - long-lived tool can get info without allocating
 *
 * at the following costs:
 *
 * - info source copy must be pinned, may be "large"
 */


struct rds_info_iterator {
	
struct page **pages;
	
void *addr;
	
unsigned long offset;
};

static DEFINE_SPINLOCK(rds_info_lock);

static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];


void rds_info_register_func(int optname, rds_info_func func) { int offset = optname - RDS_INFO_FIRST; BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); spin_lock(&rds_info_lock); BUG_ON(rds_info_funcs[offset]); rds_info_funcs[offset] = func; spin_unlock(&rds_info_lock); }

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Andy Grover56100.00%1100.00%
Total56100.00%1100.00%

EXPORT_SYMBOL_GPL(rds_info_register_func);
void rds_info_deregister_func(int optname, rds_info_func func) { int offset = optname - RDS_INFO_FIRST; BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); spin_lock(&rds_info_lock); BUG_ON(rds_info_funcs[offset] != func); rds_info_funcs[offset] = NULL; spin_unlock(&rds_info_lock); }

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Andy Grover58100.00%1100.00%
Total58100.00%1100.00%

EXPORT_SYMBOL_GPL(rds_info_deregister_func); /* * Typically we hold an atomic kmap across multiple rds_info_copy() calls * because the kmap is so expensive. This must be called before using blocking * operations while holding the mapping and as the iterator is torn down. */
void rds_info_iter_unmap(struct rds_info_iterator *iter) { if (iter->addr) { kunmap_atomic(iter->addr); iter->addr = NULL; } }

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Andy Grover31100.00%1100.00%
Total31100.00%1100.00%

/* * get_user_pages() called flush_dcache_page() on the pages for us. */
void rds_info_copy(struct rds_info_iterator *iter, void *data, unsigned long bytes) { unsigned long this; while (bytes) { if (!iter->addr) iter->addr = kmap_atomic(*iter->pages); this = min(bytes, PAGE_SIZE - iter->offset); rdsdebug("page %p addr %p offset %lu this %lu data %p " "bytes %lu\n", *iter->pages, iter->addr, iter->offset, this, data, bytes); memcpy(iter->addr + iter->offset, data, this); data += this; bytes -= this; iter->offset += this; if (iter->offset == PAGE_SIZE) { kunmap_atomic(iter->addr); iter->addr = NULL; iter->offset = 0; iter->pages++; } } }

Contributors

PersonTokensPropCommitsCommitProp
Andy Grover148100.00%2100.00%
Total148100.00%2100.00%

EXPORT_SYMBOL_GPL(rds_info_copy); /* * @optval points to the userspace buffer that the information snapshot * will be copied into. * * @optlen on input is the size of the buffer in userspace. @optlen * on output is the size of the requested snapshot in bytes. * * This function returns -errno if there is a failure, particularly -ENOSPC * if the given userspace buffer was not large enough to fit the snapshot. * On success it returns the positive number of bytes of each array element * in the snapshot. */
int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval, int __user *optlen) { struct rds_info_iterator iter; struct rds_info_lengths lens; unsigned long nr_pages = 0; unsigned long start; unsigned long i; rds_info_func func; struct page **pages = NULL; int ret; int len; int total; if (get_user(len, optlen)) { ret = -EFAULT; goto out; } /* check for all kinds of wrapping and the like */ start = (unsigned long)optval; if (len < 0 || len > INT_MAX - PAGE_SIZE + 1 || start + len < start) { ret = -EINVAL; goto out; } /* a 0 len call is just trying to probe its length */ if (len == 0) goto call_func; nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK)) >> PAGE_SHIFT; pages = kmalloc(nr_pages * sizeof(struct page *), GFP_KERNEL); if (!pages) { ret = -ENOMEM; goto out; } ret = get_user_pages_fast(start, nr_pages, 1, pages); if (ret != nr_pages) { if (ret > 0) nr_pages = ret; else nr_pages = 0; ret = -EAGAIN; /* XXX ? */ goto out; } rdsdebug("len %d nr_pages %lu\n", len, nr_pages); call_func: func = rds_info_funcs[optname - RDS_INFO_FIRST]; if (!func) { ret = -ENOPROTOOPT; goto out; } iter.pages = pages; iter.addr = NULL; iter.offset = start & (PAGE_SIZE - 1); func(sock, len, &iter, &lens); BUG_ON(lens.each == 0); total = lens.nr * lens.each; rds_info_iter_unmap(&iter); if (total > len) { len = total; ret = -ENOSPC; } else { len = total; ret = lens.each; } if (put_user(len, optlen)) ret = -EFAULT; out: for (i = 0; pages && i < nr_pages; i++) put_page(pages[i]); kfree(pages); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Andy Grover39899.00%375.00%
Dan Carpenter41.00%125.00%
Total402100.00%4100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Andy Grover75998.70%457.14%
Dan Carpenter40.52%114.29%
Tejun Heo30.39%114.29%
Paul Gortmaker30.39%114.29%
Total769100.00%7100.00%
Directory: net/rds
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