linux_dsm_epyc7002/tools/testing/nvdimm/test/iomap.c
Dan Williams 6bc756193f tools/testing/nvdimm: libnvdimm unit test infrastructure
'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>
2015-06-26 11:23:38 -04:00

152 lines
3.8 KiB
C

/*
* Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <linux/rculist.h>
#include <linux/export.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/io.h>
#include "nfit_test.h"
static LIST_HEAD(iomap_head);
static struct iomap_ops {
nfit_test_lookup_fn nfit_test_lookup;
struct list_head list;
} iomap_ops = {
.list = LIST_HEAD_INIT(iomap_ops.list),
};
void nfit_test_setup(nfit_test_lookup_fn lookup)
{
iomap_ops.nfit_test_lookup = lookup;
list_add_rcu(&iomap_ops.list, &iomap_head);
}
EXPORT_SYMBOL(nfit_test_setup);
void nfit_test_teardown(void)
{
list_del_rcu(&iomap_ops.list);
synchronize_rcu();
}
EXPORT_SYMBOL(nfit_test_teardown);
static struct nfit_test_resource *get_nfit_res(resource_size_t resource)
{
struct iomap_ops *ops;
ops = list_first_or_null_rcu(&iomap_head, typeof(*ops), list);
if (ops)
return ops->nfit_test_lookup(resource);
return NULL;
}
void __iomem *__nfit_test_ioremap(resource_size_t offset, unsigned long size,
void __iomem *(*fallback_fn)(resource_size_t, unsigned long))
{
struct nfit_test_resource *nfit_res;
rcu_read_lock();
nfit_res = get_nfit_res(offset);
rcu_read_unlock();
if (nfit_res)
return (void __iomem *) nfit_res->buf + offset
- nfit_res->res->start;
return fallback_fn(offset, size);
}
void __iomem *__wrap_ioremap_cache(resource_size_t offset, unsigned long size)
{
return __nfit_test_ioremap(offset, size, ioremap_cache);
}
EXPORT_SYMBOL(__wrap_ioremap_cache);
void __iomem *__wrap_ioremap_nocache(resource_size_t offset, unsigned long size)
{
return __nfit_test_ioremap(offset, size, ioremap_nocache);
}
EXPORT_SYMBOL(__wrap_ioremap_nocache);
void __wrap_iounmap(volatile void __iomem *addr)
{
struct nfit_test_resource *nfit_res;
rcu_read_lock();
nfit_res = get_nfit_res((unsigned long) addr);
rcu_read_unlock();
if (nfit_res)
return;
return iounmap(addr);
}
EXPORT_SYMBOL(__wrap_iounmap);
struct resource *__wrap___request_region(struct resource *parent,
resource_size_t start, resource_size_t n, const char *name,
int flags)
{
struct nfit_test_resource *nfit_res;
if (parent == &iomem_resource) {
rcu_read_lock();
nfit_res = get_nfit_res(start);
rcu_read_unlock();
if (nfit_res) {
struct resource *res = nfit_res->res + 1;
if (start + n > nfit_res->res->start
+ resource_size(nfit_res->res)) {
pr_debug("%s: start: %llx n: %llx overflow: %pr\n",
__func__, start, n,
nfit_res->res);
return NULL;
}
res->start = start;
res->end = start + n - 1;
res->name = name;
res->flags = resource_type(parent);
res->flags |= IORESOURCE_BUSY | flags;
pr_debug("%s: %pr\n", __func__, res);
return res;
}
}
return __request_region(parent, start, n, name, flags);
}
EXPORT_SYMBOL(__wrap___request_region);
void __wrap___release_region(struct resource *parent, resource_size_t start,
resource_size_t n)
{
struct nfit_test_resource *nfit_res;
if (parent == &iomem_resource) {
rcu_read_lock();
nfit_res = get_nfit_res(start);
rcu_read_unlock();
if (nfit_res) {
struct resource *res = nfit_res->res + 1;
if (start != res->start || resource_size(res) != n)
pr_info("%s: start: %llx n: %llx mismatch: %pr\n",
__func__, start, n, res);
else
memset(res, 0, sizeof(*res));
return;
}
}
__release_region(parent, start, n);
}
EXPORT_SYMBOL(__wrap___release_region);
MODULE_LICENSE("GPL v2");