2019-05-19 12:07:45 +00:00
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# SPDX-License-Identifier: GPL-2.0-only
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2007-10-19 06:41:07 +00:00
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menuconfig SAMPLES
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bool "Sample kernel code"
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help
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You can build and test sample kernel code here.
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if SAMPLES
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2020-04-29 03:45:25 +00:00
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config SAMPLE_AUXDISPLAY
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bool "auxdisplay sample"
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depends on CC_CAN_LINK
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2009-04-15 01:37:03 +00:00
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config SAMPLE_TRACE_EVENTS
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2009-05-06 02:32:32 +00:00
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tristate "Build trace_events examples -- loadable modules only"
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depends on EVENT_TRACING && m
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2009-04-15 01:37:03 +00:00
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help
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2022-03-03 22:05:32 +00:00
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This builds the trace event example module.
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config SAMPLE_TRACE_CUSTOM_EVENTS
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tristate "Build custom trace event example -- loadable modules only"
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depends on EVENT_TRACING && m
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help
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This builds the custom trace event example module.
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2009-04-15 01:37:03 +00:00
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2016-06-17 18:50:23 +00:00
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config SAMPLE_TRACE_PRINTK
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tristate "Build trace_printk module - tests various trace_printk formats"
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depends on EVENT_TRACING && m
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help
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This builds a module that calls trace_printk() and can be used to
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test various trace_printk() calls from a module.
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2019-11-08 18:12:33 +00:00
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config SAMPLE_FTRACE_DIRECT
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tristate "Build register_ftrace_direct() example"
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depends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS && m
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2021-10-12 13:38:01 +00:00
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depends on HAVE_SAMPLE_FTRACE_DIRECT
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2019-11-08 18:12:33 +00:00
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help
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This builds an ftrace direct function example
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that hooks to wake_up_process and prints the parameters.
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2021-11-15 19:56:13 +00:00
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config SAMPLE_FTRACE_DIRECT_MULTI
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2023-03-21 14:04:21 +00:00
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tristate "Build register_ftrace_direct() on multiple ips example"
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2021-11-15 19:56:13 +00:00
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depends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS && m
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depends on HAVE_SAMPLE_FTRACE_DIRECT_MULTI
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help
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This builds an ftrace direct function example
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that hooks to wake_up_process and schedule, and prints
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the function addresses.
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2023-01-03 12:49:12 +00:00
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config SAMPLE_FTRACE_OPS
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tristate "Build custom ftrace ops example"
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depends on FUNCTION_TRACER
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help
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This builds an ftrace ops example that hooks two functions and
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measures the time taken to invoke one function a number of times.
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2019-11-20 19:08:39 +00:00
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config SAMPLE_TRACE_ARRAY
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tristate "Build sample module for kernel access to Ftrace instancess"
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depends on EVENT_TRACING && m
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help
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This builds a module that demonstrates the use of various APIs to
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access Ftrace instances from within the kernel.
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2007-11-27 19:28:26 +00:00
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config SAMPLE_KOBJECT
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2019-04-27 03:33:40 +00:00
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tristate "Build kobject examples"
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2007-11-27 19:28:26 +00:00
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help
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This config option will allow you to build a number of
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different kobject sample modules showing how to use kobjects,
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ksets, and ktypes properly.
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If in doubt, say "N" here.
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2008-03-04 22:28:38 +00:00
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config SAMPLE_KPROBES
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tristate "Build kprobes examples -- loadable modules only"
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depends on KPROBES && m
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help
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This build several kprobes example modules.
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config SAMPLE_KRETPROBES
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tristate "Build kretprobes example -- loadable modules only"
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default m
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depends on SAMPLE_KPROBES && KRETPROBES
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2009-06-01 18:16:20 +00:00
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config SAMPLE_HW_BREAKPOINT
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tristate "Build kernel hardware breakpoint examples -- loadable module only"
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depends on HAVE_HW_BREAKPOINT && m
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help
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This builds kernel hardware breakpoint example modules.
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2022-03-15 14:02:00 +00:00
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config SAMPLE_FPROBE
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tristate "Build fprobe examples -- loadable modules only"
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depends on FPROBE && m
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help
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This builds a fprobe example module. This module has an option 'symbol'.
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You can specify a probed symbol or symbols separated with ','.
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2010-08-11 01:03:39 +00:00
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config SAMPLE_KFIFO
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tristate "Build kfifo examples -- loadable modules only"
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depends on m
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help
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This config option will allow you to build a number of
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different kfifo sample modules showing how to use the
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generic kfifo API.
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If in doubt, say "N" here.
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2010-10-25 15:14:05 +00:00
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config SAMPLE_KDB
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2011-03-31 01:57:33 +00:00
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tristate "Build kdb command example -- loadable modules only"
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2010-10-25 15:14:05 +00:00
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depends on KGDB_KDB && m
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help
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Build an example of how to dynamically add the hello
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command to the kdb shell.
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2017-06-26 16:02:28 +00:00
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config SAMPLE_QMI_CLIENT
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tristate "Build qmi client sample -- loadable modules only"
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depends on m
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depends on ARCH_QCOM
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2018-02-22 15:57:38 +00:00
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depends on NET
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2017-06-26 16:02:28 +00:00
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select QCOM_QMI_HELPERS
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help
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Build an QMI client sample driver, which demonstrates how to
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communicate with a remote QRTR service, using QMI encoded messages.
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2011-10-20 19:41:24 +00:00
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config SAMPLE_RPMSG_CLIENT
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tristate "Build rpmsg client sample -- loadable modules only"
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depends on RPMSG && m
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help
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Build an rpmsg client sample driver, which demonstrates how
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to communicate with an AMP-configured remote processor over
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the rpmsg bus.
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2015-02-03 22:45:18 +00:00
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config SAMPLE_LIVEPATCH
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2017-08-31 20:37:41 +00:00
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tristate "Build live patching samples -- loadable modules only"
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2015-02-03 22:45:18 +00:00
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depends on LIVEPATCH && m
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2014-12-16 17:58:20 +00:00
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help
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2017-08-31 20:37:41 +00:00
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Build sample live patch demonstrations.
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2014-12-16 17:58:20 +00:00
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2015-10-03 13:32:59 +00:00
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config SAMPLE_CONFIGFS
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tristate "Build configfs patching sample -- loadable modules only"
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depends on CONFIGFS_FS && m
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help
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Builds a sample configfs interface.
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2016-04-25 16:03:08 +00:00
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config SAMPLE_CONNECTOR
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tristate "Build connector sample -- loadable modules only"
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2019-06-04 10:13:59 +00:00
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depends on CONNECTOR && HEADERS_INSTALL && m
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2016-04-25 16:03:08 +00:00
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help
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When enabled, this builds both a sample kernel module for
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the connector interface and a user space tool to communicate
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with it.
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2019-06-27 18:39:22 +00:00
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See also Documentation/driver-api/connector.rst
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2016-04-25 16:03:08 +00:00
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2021-10-25 19:27:45 +00:00
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config SAMPLE_FANOTIFY_ERROR
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bool "Build fanotify error monitoring sample"
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2021-10-28 18:56:28 +00:00
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depends on FANOTIFY && CC_CAN_LINK && HEADERS_INSTALL
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2021-10-25 19:27:45 +00:00
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help
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When enabled, this builds an example code that uses the
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FAN_FS_ERROR fanotify mechanism to monitor filesystem
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errors.
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See also Documentation/admin-guide/filesystem-monitoring.rst.
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2019-06-04 10:13:59 +00:00
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config SAMPLE_HIDRAW
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bool "hidraw sample"
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2020-04-29 03:45:20 +00:00
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depends on CC_CAN_LINK && HEADERS_INSTALL
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2019-06-04 10:13:59 +00:00
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2021-04-22 15:41:21 +00:00
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config SAMPLE_LANDLOCK
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bool "Landlock example"
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depends on CC_CAN_LINK && HEADERS_INSTALL
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help
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Build a simple Landlock sandbox manager able to start a process
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restricted by a user-defined filesystem access control policy.
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2019-06-04 10:13:59 +00:00
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config SAMPLE_PIDFD
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bool "pidfd sample"
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2020-04-29 03:45:23 +00:00
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depends on CC_CAN_LINK && HEADERS_INSTALL
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2019-06-04 10:13:59 +00:00
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2016-07-06 06:53:19 +00:00
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config SAMPLE_SECCOMP
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2019-04-27 03:33:39 +00:00
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bool "Build seccomp sample code"
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2020-04-29 03:45:16 +00:00
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depends on SECCOMP_FILTER && CC_CAN_LINK && HEADERS_INSTALL
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2016-07-06 06:53:19 +00:00
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help
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Build samples of seccomp filters using various methods of
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BPF filter construction.
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2020-04-29 03:45:26 +00:00
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config SAMPLE_TIMER
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bool "Timer sample"
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depends on CC_CAN_LINK && HEADERS_INSTALL
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2020-04-29 03:45:19 +00:00
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config SAMPLE_UHID
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bool "UHID sample"
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depends on CC_CAN_LINK && HEADERS_INSTALL
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help
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Build UHID sample program.
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2016-12-30 15:13:30 +00:00
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config SAMPLE_VFIO_MDEV_MTTY
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2023-01-10 09:10:06 +00:00
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tristate "Build VFIO mtty example mediated device sample code"
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2023-01-26 21:08:31 +00:00
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depends on VFIO
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2023-01-10 09:10:07 +00:00
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select VFIO_MDEV
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2016-12-30 15:13:30 +00:00
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help
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Build a virtual tty sample driver for use as a VFIO
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mediated device
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2018-05-11 15:05:03 +00:00
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config SAMPLE_VFIO_MDEV_MDPY
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2023-01-10 09:10:06 +00:00
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tristate "Build VFIO mdpy example mediated device sample code"
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2023-01-26 21:08:31 +00:00
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depends on VFIO
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2023-01-10 09:10:07 +00:00
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select VFIO_MDEV
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2018-05-11 15:05:03 +00:00
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help
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Build a virtual display sample driver for use as a VFIO
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mediated device. It is a simple framebuffer and supports
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the region display interface (VFIO_GFX_PLANE_TYPE_REGION).
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2018-05-11 15:05:04 +00:00
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config SAMPLE_VFIO_MDEV_MDPY_FB
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2023-01-10 09:10:06 +00:00
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tristate "Build VFIO mdpy example guest fbdev driver"
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depends on FB
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2023-08-03 18:36:12 +00:00
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select FB_IOMEM_HELPERS
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2018-05-11 15:05:04 +00:00
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help
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Guest fbdev driver for the virtual display sample driver.
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2018-05-11 15:05:04 +00:00
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config SAMPLE_VFIO_MDEV_MBOCHS
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2023-01-30 02:13:51 +00:00
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tristate "Build VFIO mbochs example mediated device sample code"
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2023-01-26 21:08:31 +00:00
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depends on VFIO
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2023-01-10 09:10:07 +00:00
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select VFIO_MDEV
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2018-05-30 21:37:31 +00:00
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select DMA_SHARED_BUFFER
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2018-05-11 15:05:04 +00:00
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help
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Build a virtual display sample driver for use as a VFIO
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mediated device. It supports the region display interface
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(VFIO_GFX_PLANE_TYPE_DMABUF).
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Emulate enough of qemu stdvga to make bochs-drm.ko happy.
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That is basically the vram memory bar and the bochs dispi
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interface vbe registers in the mmio register bar.
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Specifically it does *not* include any legacy vga stuff.
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Device looks a lot like "qemu -device secondary-vga".
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2019-01-11 13:41:00 +00:00
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config SAMPLE_ANDROID_BINDERFS
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bool "Build Android binderfs example"
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samples: binderfs: really compile this sample and fix build issues
Even after commit c624adc9cb6e ("samples: fix binderfs sample"), this
sample is never compiled.
'hostprogs' teaches Kbuild that this is a host program, but not enough
to order to compile it. You must add it to 'always-y' to really compile
it.
Since this sample has never been compiled in upstream, various issues
are left unnoticed.
[1] compilers without <linux/android/binderfs.h> are still widely used
<linux/android/binderfs.h> is only available since commit c13295ad219d
("binderfs: rename header to binderfs.h"), i.e., Linux 5.0
If your compiler is based on UAPI headers older than Linux 5.0, you
will see the following error:
samples/binderfs/binderfs_example.c:16:10: fatal error: linux/android/binderfs.h: No such file or directory
#include <linux/android/binderfs.h>
^~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
You cannot rely on compilers having such a new header.
The common approach is to install UAPI headers of this kernel into
usr/include, and then add it to the header search path.
I added 'depends on HEADERS_INSTALL' in Kconfig, and '-I usr/include'
compiler flag in Makefile.
[2] compile the sample for target architecture
Because headers_install works for the target architecture, only the
native compiler was able to build sample code that requires
'-I usr/include'.
Commit 7f3a59db274c ("kbuild: add infrastructure to build userspace
programs") added the new syntax 'userprogs' to compile user-space
programs for the target architecture.
Use it, and then 'ifndef CROSS_COMPILE' will go away.
I added 'depends on CC_CAN_LINK' because $(CC) is not necessarily
capable of linking user-space programs.
[3] use subdir-y to descend into samples/binderfs
Since this directory does not contain any kernel-space code, it has no
point in generating built-in.a or modules.order.
Replace obj-$(CONFIG_...) with subdir-$(CONFIG_...).
[4] -Wunused-variable warning
If I compile this, I see the following warning.
samples/binderfs/binderfs_example.c: In function 'main':
samples/binderfs/binderfs_example.c:21:9: warning: unused variable 'len' [-Wunused-variable]
21 | size_t len;
| ^~~
I removed the unused 'len'.
[5] CONFIG_ANDROID_BINDERFS is not required
Since this is a user-space standalone program, it is independent of
the kernel configuration.
Remove 'depends on ANDROID_BINDERFS'.
Fixes: 9762dc1432e1 ("samples: add binderfs sample program")
Fixes: c624adc9cb6e ("samples: fix binderfs sample")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-06-07 03:20:53 +00:00
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depends on CC_CAN_LINK && HEADERS_INSTALL
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2019-01-11 13:41:00 +00:00
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help
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Builds a sample program to illustrate the use of the Android binderfs
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filesystem.
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2018-11-01 23:36:32 +00:00
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config SAMPLE_VFS
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bool "Build example programs that use new VFS system calls"
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2020-04-29 03:45:22 +00:00
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depends on CC_CAN_LINK && HEADERS_INSTALL
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statx: Add a system call to make enhanced file info available
Add a system call to make extended file information available, including
file creation and some attribute flags where available through the
underlying filesystem.
The getattr inode operation is altered to take two additional arguments: a
u32 request_mask and an unsigned int flags that indicate the
synchronisation mode. This change is propagated to the vfs_getattr*()
function.
Functions like vfs_stat() are now inline wrappers around new functions
vfs_statx() and vfs_statx_fd() to reduce stack usage.
========
OVERVIEW
========
The idea was initially proposed as a set of xattrs that could be retrieved
with getxattr(), but the general preference proved to be for a new syscall
with an extended stat structure.
A number of requests were gathered for features to be included. The
following have been included:
(1) Make the fields a consistent size on all arches and make them large.
(2) Spare space, request flags and information flags are provided for
future expansion.
(3) Better support for the y2038 problem [Arnd Bergmann] (tv_sec is an
__s64).
(4) Creation time: The SMB protocol carries the creation time, which could
be exported by Samba, which will in turn help CIFS make use of
FS-Cache as that can be used for coherency data (stx_btime).
This is also specified in NFSv4 as a recommended attribute and could
be exported by NFSD [Steve French].
(5) Lightweight stat: Ask for just those details of interest, and allow a
netfs (such as NFS) to approximate anything not of interest, possibly
without going to the server [Trond Myklebust, Ulrich Drepper, Andreas
Dilger] (AT_STATX_DONT_SYNC).
(6) Heavyweight stat: Force a netfs to go to the server, even if it thinks
its cached attributes are up to date [Trond Myklebust]
(AT_STATX_FORCE_SYNC).
And the following have been left out for future extension:
(7) Data version number: Could be used by userspace NFS servers [Aneesh
Kumar].
Can also be used to modify fill_post_wcc() in NFSD which retrieves
i_version directly, but has just called vfs_getattr(). It could get
it from the kstat struct if it used vfs_xgetattr() instead.
(There's disagreement on the exact semantics of a single field, since
not all filesystems do this the same way).
(8) BSD stat compatibility: Including more fields from the BSD stat such
as creation time (st_btime) and inode generation number (st_gen)
[Jeremy Allison, Bernd Schubert].
(9) Inode generation number: Useful for FUSE and userspace NFS servers
[Bernd Schubert].
(This was asked for but later deemed unnecessary with the
open-by-handle capability available and caused disagreement as to
whether it's a security hole or not).
(10) Extra coherency data may be useful in making backups [Andreas Dilger].
(No particular data were offered, but things like last backup
timestamp, the data version number and the DOS archive bit would come
into this category).
(11) Allow the filesystem to indicate what it can/cannot provide: A
filesystem can now say it doesn't support a standard stat feature if
that isn't available, so if, for instance, inode numbers or UIDs don't
exist or are fabricated locally...
(This requires a separate system call - I have an fsinfo() call idea
for this).
(12) Store a 16-byte volume ID in the superblock that can be returned in
struct xstat [Steve French].
(Deferred to fsinfo).
(13) Include granularity fields in the time data to indicate the
granularity of each of the times (NFSv4 time_delta) [Steve French].
(Deferred to fsinfo).
(14) FS_IOC_GETFLAGS value. These could be translated to BSD's st_flags.
Note that the Linux IOC flags are a mess and filesystems such as Ext4
define flags that aren't in linux/fs.h, so translation in the kernel
may be a necessity (or, possibly, we provide the filesystem type too).
(Some attributes are made available in stx_attributes, but the general
feeling was that the IOC flags were to ext[234]-specific and shouldn't
be exposed through statx this way).
(15) Mask of features available on file (eg: ACLs, seclabel) [Brad Boyer,
Michael Kerrisk].
(Deferred, probably to fsinfo. Finding out if there's an ACL or
seclabal might require extra filesystem operations).
(16) Femtosecond-resolution timestamps [Dave Chinner].
(A __reserved field has been left in the statx_timestamp struct for
this - if there proves to be a need).
(17) A set multiple attributes syscall to go with this.
===============
NEW SYSTEM CALL
===============
The new system call is:
int ret = statx(int dfd,
const char *filename,
unsigned int flags,
unsigned int mask,
struct statx *buffer);
The dfd, filename and flags parameters indicate the file to query, in a
similar way to fstatat(). There is no equivalent of lstat() as that can be
emulated with statx() by passing AT_SYMLINK_NOFOLLOW in flags. There is
also no equivalent of fstat() as that can be emulated by passing a NULL
filename to statx() with the fd of interest in dfd.
Whether or not statx() synchronises the attributes with the backing store
can be controlled by OR'ing a value into the flags argument (this typically
only affects network filesystems):
(1) AT_STATX_SYNC_AS_STAT tells statx() to behave as stat() does in this
respect.
(2) AT_STATX_FORCE_SYNC will require a network filesystem to synchronise
its attributes with the server - which might require data writeback to
occur to get the timestamps correct.
(3) AT_STATX_DONT_SYNC will suppress synchronisation with the server in a
network filesystem. The resulting values should be considered
approximate.
mask is a bitmask indicating the fields in struct statx that are of
interest to the caller. The user should set this to STATX_BASIC_STATS to
get the basic set returned by stat(). It should be noted that asking for
more information may entail extra I/O operations.
buffer points to the destination for the data. This must be 256 bytes in
size.
======================
MAIN ATTRIBUTES RECORD
======================
The following structures are defined in which to return the main attribute
set:
struct statx_timestamp {
__s64 tv_sec;
__s32 tv_nsec;
__s32 __reserved;
};
struct statx {
__u32 stx_mask;
__u32 stx_blksize;
__u64 stx_attributes;
__u32 stx_nlink;
__u32 stx_uid;
__u32 stx_gid;
__u16 stx_mode;
__u16 __spare0[1];
__u64 stx_ino;
__u64 stx_size;
__u64 stx_blocks;
__u64 __spare1[1];
struct statx_timestamp stx_atime;
struct statx_timestamp stx_btime;
struct statx_timestamp stx_ctime;
struct statx_timestamp stx_mtime;
__u32 stx_rdev_major;
__u32 stx_rdev_minor;
__u32 stx_dev_major;
__u32 stx_dev_minor;
__u64 __spare2[14];
};
The defined bits in request_mask and stx_mask are:
STATX_TYPE Want/got stx_mode & S_IFMT
STATX_MODE Want/got stx_mode & ~S_IFMT
STATX_NLINK Want/got stx_nlink
STATX_UID Want/got stx_uid
STATX_GID Want/got stx_gid
STATX_ATIME Want/got stx_atime{,_ns}
STATX_MTIME Want/got stx_mtime{,_ns}
STATX_CTIME Want/got stx_ctime{,_ns}
STATX_INO Want/got stx_ino
STATX_SIZE Want/got stx_size
STATX_BLOCKS Want/got stx_blocks
STATX_BASIC_STATS [The stuff in the normal stat struct]
STATX_BTIME Want/got stx_btime{,_ns}
STATX_ALL [All currently available stuff]
stx_btime is the file creation time, stx_mask is a bitmask indicating the
data provided and __spares*[] are where as-yet undefined fields can be
placed.
Time fields are structures with separate seconds and nanoseconds fields
plus a reserved field in case we want to add even finer resolution. Note
that times will be negative if before 1970; in such a case, the nanosecond
fields will also be negative if not zero.
The bits defined in the stx_attributes field convey information about a
file, how it is accessed, where it is and what it does. The following
attributes map to FS_*_FL flags and are the same numerical value:
STATX_ATTR_COMPRESSED File is compressed by the fs
STATX_ATTR_IMMUTABLE File is marked immutable
STATX_ATTR_APPEND File is append-only
STATX_ATTR_NODUMP File is not to be dumped
STATX_ATTR_ENCRYPTED File requires key to decrypt in fs
Within the kernel, the supported flags are listed by:
KSTAT_ATTR_FS_IOC_FLAGS
[Are any other IOC flags of sufficient general interest to be exposed
through this interface?]
New flags include:
STATX_ATTR_AUTOMOUNT Object is an automount trigger
These are for the use of GUI tools that might want to mark files specially,
depending on what they are.
Fields in struct statx come in a number of classes:
(0) stx_dev_*, stx_blksize.
These are local system information and are always available.
(1) stx_mode, stx_nlinks, stx_uid, stx_gid, stx_[amc]time, stx_ino,
stx_size, stx_blocks.
These will be returned whether the caller asks for them or not. The
corresponding bits in stx_mask will be set to indicate whether they
actually have valid values.
If the caller didn't ask for them, then they may be approximated. For
example, NFS won't waste any time updating them from the server,
unless as a byproduct of updating something requested.
If the values don't actually exist for the underlying object (such as
UID or GID on a DOS file), then the bit won't be set in the stx_mask,
even if the caller asked for the value. In such a case, the returned
value will be a fabrication.
Note that there are instances where the type might not be valid, for
instance Windows reparse points.
(2) stx_rdev_*.
This will be set only if stx_mode indicates we're looking at a
blockdev or a chardev, otherwise will be 0.
(3) stx_btime.
Similar to (1), except this will be set to 0 if it doesn't exist.
=======
TESTING
=======
The following test program can be used to test the statx system call:
samples/statx/test-statx.c
Just compile and run, passing it paths to the files you want to examine.
The file is built automatically if CONFIG_SAMPLES is enabled.
Here's some example output. Firstly, an NFS directory that crosses to
another FSID. Note that the AUTOMOUNT attribute is set because transiting
this directory will cause d_automount to be invoked by the VFS.
[root@andromeda ~]# /tmp/test-statx -A /warthog/data
statx(/warthog/data) = 0
results=7ff
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:26 Inode: 1703937 Links: 125
Access: (3777/drwxrwxrwx) Uid: 0 Gid: 4041
Access: 2016-11-24 09:02:12.219699527+0000
Modify: 2016-11-17 10:44:36.225653653+0000
Change: 2016-11-17 10:44:36.225653653+0000
Attributes: 0000000000001000 (-------- -------- -------- -------- -------- -------- ---m---- --------)
Secondly, the result of automounting on that directory.
[root@andromeda ~]# /tmp/test-statx /warthog/data
statx(/warthog/data) = 0
results=7ff
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:27 Inode: 2 Links: 125
Access: (3777/drwxrwxrwx) Uid: 0 Gid: 4041
Access: 2016-11-24 09:02:12.219699527+0000
Modify: 2016-11-17 10:44:36.225653653+0000
Change: 2016-11-17 10:44:36.225653653+0000
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-01-31 16:46:22 +00:00
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|
help
|
2018-11-01 23:36:32 +00:00
|
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|
Build example userspace programs that use new VFS system calls such
|
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|
as mount API and statx(). Note that this is restricted to the x86
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arch whilst it accesses system calls that aren't yet in all arches.
|
statx: Add a system call to make enhanced file info available
Add a system call to make extended file information available, including
file creation and some attribute flags where available through the
underlying filesystem.
The getattr inode operation is altered to take two additional arguments: a
u32 request_mask and an unsigned int flags that indicate the
synchronisation mode. This change is propagated to the vfs_getattr*()
function.
Functions like vfs_stat() are now inline wrappers around new functions
vfs_statx() and vfs_statx_fd() to reduce stack usage.
========
OVERVIEW
========
The idea was initially proposed as a set of xattrs that could be retrieved
with getxattr(), but the general preference proved to be for a new syscall
with an extended stat structure.
A number of requests were gathered for features to be included. The
following have been included:
(1) Make the fields a consistent size on all arches and make them large.
(2) Spare space, request flags and information flags are provided for
future expansion.
(3) Better support for the y2038 problem [Arnd Bergmann] (tv_sec is an
__s64).
(4) Creation time: The SMB protocol carries the creation time, which could
be exported by Samba, which will in turn help CIFS make use of
FS-Cache as that can be used for coherency data (stx_btime).
This is also specified in NFSv4 as a recommended attribute and could
be exported by NFSD [Steve French].
(5) Lightweight stat: Ask for just those details of interest, and allow a
netfs (such as NFS) to approximate anything not of interest, possibly
without going to the server [Trond Myklebust, Ulrich Drepper, Andreas
Dilger] (AT_STATX_DONT_SYNC).
(6) Heavyweight stat: Force a netfs to go to the server, even if it thinks
its cached attributes are up to date [Trond Myklebust]
(AT_STATX_FORCE_SYNC).
And the following have been left out for future extension:
(7) Data version number: Could be used by userspace NFS servers [Aneesh
Kumar].
Can also be used to modify fill_post_wcc() in NFSD which retrieves
i_version directly, but has just called vfs_getattr(). It could get
it from the kstat struct if it used vfs_xgetattr() instead.
(There's disagreement on the exact semantics of a single field, since
not all filesystems do this the same way).
(8) BSD stat compatibility: Including more fields from the BSD stat such
as creation time (st_btime) and inode generation number (st_gen)
[Jeremy Allison, Bernd Schubert].
(9) Inode generation number: Useful for FUSE and userspace NFS servers
[Bernd Schubert].
(This was asked for but later deemed unnecessary with the
open-by-handle capability available and caused disagreement as to
whether it's a security hole or not).
(10) Extra coherency data may be useful in making backups [Andreas Dilger].
(No particular data were offered, but things like last backup
timestamp, the data version number and the DOS archive bit would come
into this category).
(11) Allow the filesystem to indicate what it can/cannot provide: A
filesystem can now say it doesn't support a standard stat feature if
that isn't available, so if, for instance, inode numbers or UIDs don't
exist or are fabricated locally...
(This requires a separate system call - I have an fsinfo() call idea
for this).
(12) Store a 16-byte volume ID in the superblock that can be returned in
struct xstat [Steve French].
(Deferred to fsinfo).
(13) Include granularity fields in the time data to indicate the
granularity of each of the times (NFSv4 time_delta) [Steve French].
(Deferred to fsinfo).
(14) FS_IOC_GETFLAGS value. These could be translated to BSD's st_flags.
Note that the Linux IOC flags are a mess and filesystems such as Ext4
define flags that aren't in linux/fs.h, so translation in the kernel
may be a necessity (or, possibly, we provide the filesystem type too).
(Some attributes are made available in stx_attributes, but the general
feeling was that the IOC flags were to ext[234]-specific and shouldn't
be exposed through statx this way).
(15) Mask of features available on file (eg: ACLs, seclabel) [Brad Boyer,
Michael Kerrisk].
(Deferred, probably to fsinfo. Finding out if there's an ACL or
seclabal might require extra filesystem operations).
(16) Femtosecond-resolution timestamps [Dave Chinner].
(A __reserved field has been left in the statx_timestamp struct for
this - if there proves to be a need).
(17) A set multiple attributes syscall to go with this.
===============
NEW SYSTEM CALL
===============
The new system call is:
int ret = statx(int dfd,
const char *filename,
unsigned int flags,
unsigned int mask,
struct statx *buffer);
The dfd, filename and flags parameters indicate the file to query, in a
similar way to fstatat(). There is no equivalent of lstat() as that can be
emulated with statx() by passing AT_SYMLINK_NOFOLLOW in flags. There is
also no equivalent of fstat() as that can be emulated by passing a NULL
filename to statx() with the fd of interest in dfd.
Whether or not statx() synchronises the attributes with the backing store
can be controlled by OR'ing a value into the flags argument (this typically
only affects network filesystems):
(1) AT_STATX_SYNC_AS_STAT tells statx() to behave as stat() does in this
respect.
(2) AT_STATX_FORCE_SYNC will require a network filesystem to synchronise
its attributes with the server - which might require data writeback to
occur to get the timestamps correct.
(3) AT_STATX_DONT_SYNC will suppress synchronisation with the server in a
network filesystem. The resulting values should be considered
approximate.
mask is a bitmask indicating the fields in struct statx that are of
interest to the caller. The user should set this to STATX_BASIC_STATS to
get the basic set returned by stat(). It should be noted that asking for
more information may entail extra I/O operations.
buffer points to the destination for the data. This must be 256 bytes in
size.
======================
MAIN ATTRIBUTES RECORD
======================
The following structures are defined in which to return the main attribute
set:
struct statx_timestamp {
__s64 tv_sec;
__s32 tv_nsec;
__s32 __reserved;
};
struct statx {
__u32 stx_mask;
__u32 stx_blksize;
__u64 stx_attributes;
__u32 stx_nlink;
__u32 stx_uid;
__u32 stx_gid;
__u16 stx_mode;
__u16 __spare0[1];
__u64 stx_ino;
__u64 stx_size;
__u64 stx_blocks;
__u64 __spare1[1];
struct statx_timestamp stx_atime;
struct statx_timestamp stx_btime;
struct statx_timestamp stx_ctime;
struct statx_timestamp stx_mtime;
__u32 stx_rdev_major;
__u32 stx_rdev_minor;
__u32 stx_dev_major;
__u32 stx_dev_minor;
__u64 __spare2[14];
};
The defined bits in request_mask and stx_mask are:
STATX_TYPE Want/got stx_mode & S_IFMT
STATX_MODE Want/got stx_mode & ~S_IFMT
STATX_NLINK Want/got stx_nlink
STATX_UID Want/got stx_uid
STATX_GID Want/got stx_gid
STATX_ATIME Want/got stx_atime{,_ns}
STATX_MTIME Want/got stx_mtime{,_ns}
STATX_CTIME Want/got stx_ctime{,_ns}
STATX_INO Want/got stx_ino
STATX_SIZE Want/got stx_size
STATX_BLOCKS Want/got stx_blocks
STATX_BASIC_STATS [The stuff in the normal stat struct]
STATX_BTIME Want/got stx_btime{,_ns}
STATX_ALL [All currently available stuff]
stx_btime is the file creation time, stx_mask is a bitmask indicating the
data provided and __spares*[] are where as-yet undefined fields can be
placed.
Time fields are structures with separate seconds and nanoseconds fields
plus a reserved field in case we want to add even finer resolution. Note
that times will be negative if before 1970; in such a case, the nanosecond
fields will also be negative if not zero.
The bits defined in the stx_attributes field convey information about a
file, how it is accessed, where it is and what it does. The following
attributes map to FS_*_FL flags and are the same numerical value:
STATX_ATTR_COMPRESSED File is compressed by the fs
STATX_ATTR_IMMUTABLE File is marked immutable
STATX_ATTR_APPEND File is append-only
STATX_ATTR_NODUMP File is not to be dumped
STATX_ATTR_ENCRYPTED File requires key to decrypt in fs
Within the kernel, the supported flags are listed by:
KSTAT_ATTR_FS_IOC_FLAGS
[Are any other IOC flags of sufficient general interest to be exposed
through this interface?]
New flags include:
STATX_ATTR_AUTOMOUNT Object is an automount trigger
These are for the use of GUI tools that might want to mark files specially,
depending on what they are.
Fields in struct statx come in a number of classes:
(0) stx_dev_*, stx_blksize.
These are local system information and are always available.
(1) stx_mode, stx_nlinks, stx_uid, stx_gid, stx_[amc]time, stx_ino,
stx_size, stx_blocks.
These will be returned whether the caller asks for them or not. The
corresponding bits in stx_mask will be set to indicate whether they
actually have valid values.
If the caller didn't ask for them, then they may be approximated. For
example, NFS won't waste any time updating them from the server,
unless as a byproduct of updating something requested.
If the values don't actually exist for the underlying object (such as
UID or GID on a DOS file), then the bit won't be set in the stx_mask,
even if the caller asked for the value. In such a case, the returned
value will be a fabrication.
Note that there are instances where the type might not be valid, for
instance Windows reparse points.
(2) stx_rdev_*.
This will be set only if stx_mode indicates we're looking at a
blockdev or a chardev, otherwise will be 0.
(3) stx_btime.
Similar to (1), except this will be set to 0 if it doesn't exist.
=======
TESTING
=======
The following test program can be used to test the statx system call:
samples/statx/test-statx.c
Just compile and run, passing it paths to the files you want to examine.
The file is built automatically if CONFIG_SAMPLES is enabled.
Here's some example output. Firstly, an NFS directory that crosses to
another FSID. Note that the AUTOMOUNT attribute is set because transiting
this directory will cause d_automount to be invoked by the VFS.
[root@andromeda ~]# /tmp/test-statx -A /warthog/data
statx(/warthog/data) = 0
results=7ff
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:26 Inode: 1703937 Links: 125
Access: (3777/drwxrwxrwx) Uid: 0 Gid: 4041
Access: 2016-11-24 09:02:12.219699527+0000
Modify: 2016-11-17 10:44:36.225653653+0000
Change: 2016-11-17 10:44:36.225653653+0000
Attributes: 0000000000001000 (-------- -------- -------- -------- -------- -------- ---m---- --------)
Secondly, the result of automounting on that directory.
[root@andromeda ~]# /tmp/test-statx /warthog/data
statx(/warthog/data) = 0
results=7ff
Size: 4096 Blocks: 8 IO Block: 1048576 directory
Device: 00:27 Inode: 2 Links: 125
Access: (3777/drwxrwxrwx) Uid: 0 Gid: 4041
Access: 2016-11-24 09:02:12.219699527+0000
Modify: 2016-11-17 10:44:36.225653653+0000
Change: 2016-11-17 10:44:36.225653653+0000
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-01-31 16:46:22 +00:00
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|
2019-10-10 13:27:10 +00:00
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config SAMPLE_INTEL_MEI
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bool "Build example program working with intel mei driver"
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depends on INTEL_MEI
|
2020-04-29 03:45:24 +00:00
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depends on CC_CAN_LINK && HEADERS_INSTALL
|
2019-10-10 13:27:10 +00:00
|
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|
help
|
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|
Build a sample program to work with mei device.
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2023-05-11 09:51:26 +00:00
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config SAMPLE_TPS6594_PFSM
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bool "Build example program working with TPS6594 PFSM driver"
|
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depends on HEADERS_INSTALL
|
2023-06-16 14:50:10 +00:00
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depends on CC_CAN_LINK
|
2023-05-11 09:51:26 +00:00
|
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|
help
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|
Build a sample program to work with PFSM devices.
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|
2020-04-29 03:45:27 +00:00
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config SAMPLE_WATCHDOG
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bool "watchdog sample"
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|
depends on CC_CAN_LINK
|
2019-10-10 13:27:10 +00:00
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|
2020-01-14 17:07:11 +00:00
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config SAMPLE_WATCH_QUEUE
|
2020-11-24 20:28:02 +00:00
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bool "Build example watch_queue notification API consumer"
|
2020-06-17 02:08:38 +00:00
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depends on CC_CAN_LINK && HEADERS_INSTALL
|
2020-01-14 17:07:11 +00:00
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|
help
|
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|
|
|
Build example userspace program to use the new mount_notify(),
|
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sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function.
|
2019-10-10 13:27:10 +00:00
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2021-11-24 20:00:36 +00:00
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config SAMPLE_CORESIGHT_SYSCFG
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tristate "Build example loadable module for CoreSight config"
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depends on CORESIGHT && m
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help
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|
|
Build an example loadable module that adds new CoreSight features
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and configuration using the CoreSight system configuration API.
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This demonstrates how a user may create their own CoreSight
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configurations and easily load them into the system at runtime.
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2023-03-30 06:09:04 +00:00
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config SAMPLE_KMEMLEAK
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tristate "Simple test for the kernel memory leak detector"
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depends on DEBUG_KMEMLEAK && m
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help
|
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|
|
Build a sample program which have explicitly leaks memory to test
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kmemleak
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2023-11-23 07:19:43 +00:00
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config SAMPLE_CGROUP
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bool "Build cgroup sample code"
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|
depends on CGROUPS && CC_CAN_LINK && HEADERS_INSTALL
|
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|
help
|
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|
|
|
Build samples that demonstrate the usage of the cgroup API.
|
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|
2021-07-03 15:21:12 +00:00
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source "samples/rust/Kconfig"
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2007-10-19 06:41:07 +00:00
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endif # SAMPLES
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config HAVE_SAMPLE_FTRACE_DIRECT
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bool
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config HAVE_SAMPLE_FTRACE_DIRECT_MULTI
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bool
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