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6bc756193f
'libnvdimm' is the first driver sub-system in the kernel to implement mocking for unit test coverage. The nfit_test module gets built as an external module and arranges for external module replacements of nfit, libnvdimm, nd_pmem, and nd_blk. These replacements use the linker --wrap option to redirect calls to ioremap() + request_mem_region() to custom defined unit test resources. The end result is a fully functional nvdimm_bus, as far as userspace is concerned, but with the capability to perform otherwise destructive tests on emulated resources. Q: Why not use QEMU for this emulation? QEMU is not suitable for unit testing. QEMU's role is to faithfully emulate the platform. A unit test's role is to unfaithfully implement the platform with the goal of triggering bugs in the corners of the sub-system implementation. As bugs are discovered in platforms, or the sub-system itself, the unit tests are extended to backstop a fix with a reproducer unit test. Another problem with QEMU is that it would require coordination of 3 software projects instead of 2 (kernel + libndctl [1]) to maintain and execute the tests. The chances for bit rot and the difficulty of getting the tests running goes up non-linearly the more components involved. Q: Why submit this to the kernel tree instead of external modules in libndctl? Simple, to alleviate the same risk that out-of-tree external modules face. Updates to drivers/nvdimm/ can be immediately evaluated to see if they have any impact on tools/testing/nvdimm/. Q: What are the negative implications of merging this? It is a unique maintenance burden because the purpose of mocking an interface to enable a unit test is to purposefully short circuit the semantics of a routine to enable testing. For example __wrap_ioremap_cache() fakes the pmem driver into "ioremap()'ing" a test resource buffer allocated by dma_alloc_coherent(). The future maintenance burden hits when someone changes the semantics of ioremap_cache() and wonders what the implications are for the unit test. [1]: https://github.com/pmem/ndctl Cc: <linux-acpi@vger.kernel.org> Cc: Lv Zheng <lv.zheng@intel.com> Cc: Robert Moore <robert.moore@intel.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
152 lines
3.8 KiB
C
152 lines
3.8 KiB
C
/*
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* Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/rculist.h>
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#include <linux/export.h>
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#include <linux/ioport.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/io.h>
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#include "nfit_test.h"
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static LIST_HEAD(iomap_head);
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static struct iomap_ops {
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nfit_test_lookup_fn nfit_test_lookup;
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struct list_head list;
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} iomap_ops = {
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.list = LIST_HEAD_INIT(iomap_ops.list),
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};
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void nfit_test_setup(nfit_test_lookup_fn lookup)
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{
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iomap_ops.nfit_test_lookup = lookup;
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list_add_rcu(&iomap_ops.list, &iomap_head);
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}
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EXPORT_SYMBOL(nfit_test_setup);
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void nfit_test_teardown(void)
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{
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list_del_rcu(&iomap_ops.list);
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synchronize_rcu();
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}
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EXPORT_SYMBOL(nfit_test_teardown);
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static struct nfit_test_resource *get_nfit_res(resource_size_t resource)
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{
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struct iomap_ops *ops;
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ops = list_first_or_null_rcu(&iomap_head, typeof(*ops), list);
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if (ops)
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return ops->nfit_test_lookup(resource);
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return NULL;
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}
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void __iomem *__nfit_test_ioremap(resource_size_t offset, unsigned long size,
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void __iomem *(*fallback_fn)(resource_size_t, unsigned long))
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{
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struct nfit_test_resource *nfit_res;
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rcu_read_lock();
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nfit_res = get_nfit_res(offset);
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rcu_read_unlock();
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if (nfit_res)
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return (void __iomem *) nfit_res->buf + offset
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- nfit_res->res->start;
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return fallback_fn(offset, size);
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}
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void __iomem *__wrap_ioremap_cache(resource_size_t offset, unsigned long size)
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{
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return __nfit_test_ioremap(offset, size, ioremap_cache);
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}
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EXPORT_SYMBOL(__wrap_ioremap_cache);
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void __iomem *__wrap_ioremap_nocache(resource_size_t offset, unsigned long size)
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{
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return __nfit_test_ioremap(offset, size, ioremap_nocache);
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}
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EXPORT_SYMBOL(__wrap_ioremap_nocache);
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void __wrap_iounmap(volatile void __iomem *addr)
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{
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struct nfit_test_resource *nfit_res;
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rcu_read_lock();
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nfit_res = get_nfit_res((unsigned long) addr);
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rcu_read_unlock();
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if (nfit_res)
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return;
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return iounmap(addr);
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}
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EXPORT_SYMBOL(__wrap_iounmap);
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struct resource *__wrap___request_region(struct resource *parent,
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resource_size_t start, resource_size_t n, const char *name,
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int flags)
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{
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struct nfit_test_resource *nfit_res;
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if (parent == &iomem_resource) {
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rcu_read_lock();
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nfit_res = get_nfit_res(start);
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rcu_read_unlock();
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if (nfit_res) {
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struct resource *res = nfit_res->res + 1;
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if (start + n > nfit_res->res->start
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+ resource_size(nfit_res->res)) {
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pr_debug("%s: start: %llx n: %llx overflow: %pr\n",
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__func__, start, n,
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nfit_res->res);
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return NULL;
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}
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res->start = start;
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res->end = start + n - 1;
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res->name = name;
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res->flags = resource_type(parent);
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res->flags |= IORESOURCE_BUSY | flags;
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pr_debug("%s: %pr\n", __func__, res);
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return res;
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}
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}
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return __request_region(parent, start, n, name, flags);
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}
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EXPORT_SYMBOL(__wrap___request_region);
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void __wrap___release_region(struct resource *parent, resource_size_t start,
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resource_size_t n)
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{
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struct nfit_test_resource *nfit_res;
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if (parent == &iomem_resource) {
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rcu_read_lock();
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nfit_res = get_nfit_res(start);
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rcu_read_unlock();
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if (nfit_res) {
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struct resource *res = nfit_res->res + 1;
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if (start != res->start || resource_size(res) != n)
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pr_info("%s: start: %llx n: %llx mismatch: %pr\n",
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__func__, start, n, res);
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else
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memset(res, 0, sizeof(*res));
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return;
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}
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}
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__release_region(parent, start, n);
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}
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EXPORT_SYMBOL(__wrap___release_region);
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MODULE_LICENSE("GPL v2");
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