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2024-02-20 ea08eeccae9297f7aabd2ef7f0c2517ac4549acc

 kernel/Documentation/admin-guide/dynamic-debug-howto.rst
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 ``print_hex_dump_debug()``/``print_hex_dump_bytes()`` calls can be dynamically
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 enabled per-callsite.
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+If you do not want to enable dynamic debug globally (i.e. in some embedded
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+system), you may set ``CONFIG_DYNAMIC_DEBUG_CORE`` as basic support of dynamic
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+debug and add ``ccflags := -DDYNAMIC_DEBUG_MODULE`` into the Makefile of any
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+modules which you'd like to dynamically debug later.
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+
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 If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``print_hex_dump_debug()`` is just
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 shortcut for ``print_hex_dump(KERN_DEBUG)``.
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   nullarbor:~ # cat <debugfs>/dynamic_debug/control
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   # filename:lineno [module]function flags format
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-  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:323 [svcxprt_rdma]svc_rdma_cleanup =_ "SVCRDMA Module Removed, deregister RPC RDMA transport\012"
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-  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:341 [svcxprt_rdma]svc_rdma_init =_ "\011max_inline       : %d\012"
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-  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:340 [svcxprt_rdma]svc_rdma_init =_ "\011sq_depth         : %d\012"
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-  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:338 [svcxprt_rdma]svc_rdma_init =_ "\011max_requests     : %d\012"
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+  net/sunrpc/svc_rdma.c:323 [svcxprt_rdma]svc_rdma_cleanup =_ "SVCRDMA Module Removed, deregister RPC RDMA transport\012"
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+  net/sunrpc/svc_rdma.c:341 [svcxprt_rdma]svc_rdma_init =_ "\011max_inline       : %d\012"
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+  net/sunrpc/svc_rdma.c:340 [svcxprt_rdma]svc_rdma_init =_ "\011sq_depth         : %d\012"
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+  net/sunrpc/svc_rdma.c:338 [svcxprt_rdma]svc_rdma_init =_ "\011max_requests     : %d\012"
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   ...
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   nullarbor:~ # awk '$3 != "=_"' <debugfs>/dynamic_debug/control
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   # filename:lineno [module]function flags format
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-  /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c:1603 [sunrpc]svc_send p "svc_process: st_sendto returned %d\012"
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+  net/sunrpc/svcsock.c:1603 [sunrpc]svc_send p "svc_process: st_sendto returned %d\012"
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 Command Language Reference
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 ==========================
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   ~# cat query-batch-file > <debugfs>/dynamic_debug/control
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-A another way is to use wildcard. The match rule support ``*`` (matches
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-zero or more characters) and ``?`` (matches exactly one character).For
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+Another way is to use wildcards. The match rule supports ``*`` (matches
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+zero or more characters) and ``?`` (matches exactly one character). For
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 example, you can match all usb drivers::
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   ~# echo "file drivers/usb/* +p" > <debugfs>/dynamic_debug/control
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     of each callsite.  Example::
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 	func svc_tcp_accept
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+	func *recv*		# in rfcomm, bluetooth, ping, tcp
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 file
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-    The given string is compared against either the full pathname, the
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-    src-root relative pathname, or the basename of the source file of
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-    each callsite.  Examples::
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+    The given string is compared against either the src-root relative
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+    pathname, or the basename of the source file of each callsite.
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+    Examples::
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 	file svcsock.c
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-	file kernel/freezer.c
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-	file /usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c
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+	file kernel/freezer.c	# ie column 1 of control file
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+	file drivers/usb/*	# all callsites under it
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+	file inode.c:start_*	# parse :tail as a func (above)
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+	file inode.c:1-100	# parse :tail as a line-range (above)
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 module
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     The given string is compared against the module name
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 	module sunrpc
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 	module nfsd
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+	module drm*	# both drm, drm_kms_helper
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 format
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     The given string is searched for in the dynamic debug format
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 bootloader may impose lower limits.
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 These ``dyndbg`` params are processed just after the ddebug tables are
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-processed, as part of the arch_initcall.  Thus you can enable debug
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-messages in all code run after this arch_initcall via this boot
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+processed, as part of the early_initcall.  Thus you can enable debug
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+messages in all code run after this early_initcall via this boot
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 parameter.
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 On an x86 system for example ACPI enablement is a subsys_initcall and::
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 If ``foo`` module is not built-in, ``foo.dyndbg`` will still be processed at
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 boot time, without effect, but will be reprocessed when module is
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-loaded later. ``dyndbg_query=`` and bare ``dyndbg=`` are only processed at
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+loaded later. ``ddebug_query=`` and bare ``dyndbg=`` are only processed at
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 boot.
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 For ``CONFIG_DYNAMIC_DEBUG`` kernels, any settings given at boot-time (or
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 enabled by ``-DDEBUG`` flag during compilation) can be disabled later via
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-the sysfs interface if the debug messages are no longer needed::
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+the debugfs interface if the debug messages are no longer needed::
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    echo "module module_name -p" > <debugfs>/dynamic_debug/control
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