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39 .Nd kernel symbol table interface
45 character device provides a read-only interface to a snapshot of the kernel
46 symbol table. The in-kernel symbol manager is designed to be able to handle
47 many types of symbols tables, however, only
49 symbol tables are supported by this device. The ELF format image contains two
50 sections: a symbol table and a corresponding string table.
51 .Bl -tag -width indent -offset indent
53 The SYMTAB section contains the symbol table entries present in the current
54 running kernel, including the symbol table entries of any loaded modules. The
55 symbols are ordered by the kernel module load time starting with kernel file
56 symbols first, followed by the first loaded module's symbols and so on.
58 The STRTAB section contains the symbol name strings from the kernel and any
59 loaded modules that the symbol table entries reference.
62 Elf formated symbol table data read from the
64 file represents the state of the kernel at the time when the device is opened.
67 has no text or data, most of the fields are initialized to NULL.
70 driver does not block the loading or unloading of modules into the kernel
73 file is open but may contain stale data.
77 command codes below are defined in
80 The (third) argument to the
82 should be a pointer to the type indicated.
83 .Bl -tag -width indent -offset indent
84 .It Dv KIOCGSIZE (size_t)
85 Returns the total size of the current symbol table.
86 This can be used when allocating a buffer to make a copy of
87 the kernel symbol table.
88 .It Dv KIOCGADDR (void *)
89 Returns the address of the kernel symbol table mapped in
93 .Bl -tag -width /dev/ksymsX
104 The device is already open. A process must close
106 before it can be opened again.
108 There is a resource shortage in the kernel.
110 The driver was unsuccessful in creating a snapshot of the kernel symbol
111 table. 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
138 .Aq sson@FreeBSD.org .
140 Because files can be dynamically linked into the kernel at any time the symbol
141 information can vary. When you open the
143 file, you have access to an ELF image which represents a snapshot of the state of the kernel symbol information at that instant in time. Keeping the device open does not block the loading or unloading of kernel modules. To get a new snapshot you must close and re-open the device.
145 A process is only allowed to open the
147 file once at a time. The process must close the
149 before it is allowed to open it again.
153 driver uses the calling process' memory address space to store the snapshot.
155 can be used to get the memory address where the symbol table is stored to
158 may also be used but it will map it to another address.