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35 .Nd kernel symbol table interface
41 character device provides a read-only interface to a snapshot of the kernel
43 The in-kernel symbol manager is designed to be able to handle
44 many types of symbols tables, however, only
46 symbol tables are supported by this device.
47 The ELF format image contains two
48 sections: a symbol table and a corresponding string table.
49 .Bl -tag -width indent -offset indent
51 The SYMTAB section contains the symbol table entries present in the current
52 running kernel, including the symbol table entries of any loaded modules.
53 The symbols are ordered by the kernel module load time starting with kernel file
54 symbols first, followed by the first loaded module's symbols and so on.
56 The STRTAB section contains the symbol name strings from the kernel and any
57 loaded modules that the symbol table entries reference.
60 Elf formatted symbol table data read from the
62 file represents the state of the kernel at the time when the device is opened.
65 has no text or data, most of the fields are initialized to NULL.
68 driver does not block the loading or unloading of modules into the kernel
71 file is open but may contain stale data.
75 command codes below are defined in
78 The (third) argument to the
80 should be a pointer to the type indicated.
81 .Bl -tag -width indent -offset indent
82 .It Dv KIOCGSIZE (size_t)
83 Returns the total size of the current symbol table.
84 This can be used when allocating a buffer to make a copy of
85 the kernel symbol table.
86 .It Dv KIOCGADDR (void *)
87 Returns the address of the kernel symbol table mapped in
91 .Bl -tag -width /dev/ksymsX
102 The device is already open.
105 before it can be opened again.
107 There is a resource shortage in the kernel.
109 The driver was unsuccessful in creating a snapshot of the kernel symbol
111 This may occur if the kernel was in the process of loading or
122 device exists in many different operating systems.
123 This implementation is similar in function to the Solaris and NetBSD
129 driver first appeared in
136 driver was written by
137 .An Stacey Son Aq Mt sson@FreeBSD.org .
139 Because files can be dynamically linked into the kernel at any time the symbol
140 information can vary.
143 file, you have access to an ELF image which represents a snapshot of the state
144 of the kernel symbol information at that instant in time.
145 Keeping the device open does not block the loading or unloading of kernel
147 To get a new snapshot you must close and re-open the device.
149 A process is only allowed to open the
152 The process must close the
154 before it is allowed to open it again.
158 driver uses the calling process' memory address space to store the snapshot.
160 can be used to get the memory address where the symbol table is stored to
163 may also be used but it will map it to another address.