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iommu: Enable debugfs exposure of IOMMU driver internals

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Provide base enablement for using debugfs to expose internal data of an
IOMMU driver. When called, create the /sys/kernel/debug/iommu directory.

Emit a strong warning at boot time to indicate that this feature is
enabled.

This function is called from iommu_init, and creates the initial DebugFS
directory. Drivers may then call iommu_debugfs_new_driver_dir() to
instantiate a device-specific directory to expose internal data.
It will return a pointer to the new dentry structure created in
/sys/kernel/debug/iommu, or NULL in the event of a failure.

Since the IOMMU driver can not be removed from the running system, there
is no need for an "off" function.

Signed-off-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Gary R Hook 2018-06-12 16:41:21 -05:00 committed by Joerg Roedel
parent 021c91791a
commit bad614b242
5 changed files with 86 additions and 0 deletions
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10
drivers/iommu/Kconfig
View File

@ -60,6 +60,16 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
endmenu
config IOMMU_DEBUGFS
bool "Export IOMMU internals in DebugFS"
depends on DEBUG_FS
help
Allows exposure of IOMMU device internals. This option enables
the use of debugfs by IOMMU drivers as required. Devices can,
at initialization time, cause the IOMMU code to create a top-level
debug/iommu directory, and then populate a subdirectory with
entries as required.
config IOMMU_IOVA
tristate

1
drivers/iommu/Makefile
View File

@ -2,6 +2,7 @@
obj-$(CONFIG_IOMMU_API) += iommu.o
obj-$(CONFIG_IOMMU_API) += iommu-traces.o
obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
obj-$(CONFIG_IOMMU_DEBUGFS) += iommu-debugfs.o
obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o

66
drivers/iommu/iommu-debugfs.c Normal file
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@ -0,0 +1,66 @@
// SPDX-License-Identifier: GPL-2.0
/*
* IOMMU debugfs core infrastructure
*
* Copyright (C) 2018 Advanced Micro Devices, Inc.
*
* Author: Gary R Hook <gary.hook@amd.com>
*/
#include <linux/pci.h>
#include <linux/iommu.h>
#include <linux/debugfs.h>
struct dentry *iommu_debugfs_dir;
/**
* iommu_debugfs_setup - create the top-level iommu directory in debugfs
*
* Provide base enablement for using debugfs to expose internal data of an
* IOMMU driver. When called, this function creates the
* /sys/kernel/debug/iommu directory.
*
* Emit a strong warning at boot time to indicate that this feature is
* enabled.
*
* This function is called from iommu_init; drivers may then call
* iommu_debugfs_new_driver_dir() to instantiate a vendor-specific
* directory to be used to expose internal data.
*/
void iommu_debugfs_setup(void)
{
if (!iommu_debugfs_dir) {
iommu_debugfs_dir = debugfs_create_dir("iommu", NULL);
pr_warn("\n");
pr_warn("*************************************************************\n");
pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
pr_warn("** **\n");
pr_warn("** IOMMU DebugFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL **\n");
pr_warn("** **\n");
pr_warn("** This means that this kernel is built to expose internal **\n");
pr_warn("** IOMMU data structures, which may compromise security on **\n");
pr_warn("** your system. **\n");
pr_warn("** **\n");
pr_warn("** If you see this message and you are not debugging the **\n");
pr_warn("** kernel, report this immediately to your vendor! **\n");
pr_warn("** **\n");
pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
pr_warn("*************************************************************\n");
}
}
/**
* iommu_debugfs_new_driver_dir - create a vendor directory under debugfs/iommu
* @vendor: name of the vendor-specific subdirectory to create
*
* This function is called by an IOMMU driver to create the top-level debugfs
* directory for that driver.
*
* Return: upon success, a pointer to the dentry for the new directory.
* NULL in case of failure.
*/
struct dentry *iommu_debugfs_new_driver_dir(const char *vendor)
{
return debugfs_create_dir(vendor, iommu_debugfs_dir);
}
EXPORT_SYMBOL_GPL(iommu_debugfs_new_driver_dir);

2
drivers/iommu/iommu.c
View File

@ -1748,6 +1748,8 @@ static int __init iommu_init(void)
NULL, kernel_kobj);
BUG_ON(!iommu_group_kset);
iommu_debugfs_setup();
return 0;
}
core_initcall(iommu_init);

7
include/linux/iommu.h
View File

@ -698,4 +698,11 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
#endif /* CONFIG_IOMMU_API */
#ifdef CONFIG_IOMMU_DEBUGFS
extern struct dentry *iommu_debugfs_dir;
void iommu_debugfs_setup(void);
#else
static inline void iommu_debugfs_setup(void) {}
#endif
#endif /* __LINUX_IOMMU_H */