Clean up #include's in the SYNOPSIS.
[dragonfly.git] / lib / libkvm / kvm_read.3
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36.\" @(#)kvm_read.3 8.1 (Berkeley) 6/4/93
37.\" $FreeBSD: src/lib/libkvm/kvm_read.3,v 1.6.2.3 2001/12/17 10:08:30 ru Exp $
6b7bde44 38.\" $DragonFly: src/lib/libkvm/kvm_read.3,v 1.4 2008/09/07 08:36:54 swildner Exp $
984263bc 39.\"
dece1c51 40.Dd January 8, 2006
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41.Dt KVM_READ 3
42.Os
43.Sh NAME
44.Nm kvm_read ,
6b7bde44 45.Nm kvm_readstr ,
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46.Nm kvm_write
47.Nd read or write kernel virtual memory
48.Sh LIBRARY
49.Lb libkvm
50.Sh SYNOPSIS
a9f0312e 51.In sys/types.h
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52.In kvm.h
53.Ft ssize_t
54.Fn kvm_read "kvm_t *kd" "unsigned long addr" "void *buf" "size_t nbytes"
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55.Ft "char *"
56.Fn kvm_readstr "kvm_t *kd" "unsigned long addr" "char *buf" "size_t *len"
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57.Ft ssize_t
58.Fn kvm_write "kvm_t *kd" "unsigned long addr" "const void *buf" "size_t nbytes"
59.Sh DESCRIPTION
60The
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61.Fn kvm_read ,
62.Fn kvm_readstr
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63and
64.Fn kvm_write
65functions are used to read and write kernel virtual memory (or a crash
66dump file). See
67.Fn kvm_open 3
68or
69.Fn kvm_openfiles 3
70for information regarding opening kernel virtual memory and crash dumps.
71.Pp
72The
73.Fn kvm_read
74function transfers
75.Fa nbytes
76bytes of data from
77the kernel space address
78.Fa addr
79to
80.Fa buf .
81Conversely,
82.Fn kvm_write
83transfers data from
84.Fa buf
85to
86.Fa addr .
87Unlike their SunOS counterparts, these functions cannot be used to
88read or write process address spaces.
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89.Pp
90The
91.Fn kvm_readstr
92function exists for convenience to read NUL terminated strings
93from the kernel address space.
94If
95.Fa buf
96is
97.Dv NULL ,
98.Fn kvm_readstr
99will allocate a sufficiently large buffer, which needs to be
100deallocated via
101.Xr free 3
102by the caller.
103If
104.Fa len
105is not
106.Dv NULL ,
107.Fn kvm_readstr
108will interpret the value it is pointing to as the size of
109.Fa buf
110and will store the size of the complete string at
111.Fa addr .
112Note that if only
113.Fa buf
114is too small to hold the complete string,
115.Fn kvm_readstr
116will return
117.Dv NULL
118but set
119.Fa len
120to the size needed.
984263bc 121.Sh RETURN VALUES
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122For
123.Fn kvm_read
124and
125.Fn kvm_write
126the number of bytes actually transferred is returned, if the request
127was successful.
984263bc 128Otherwise, -1 is returned.
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129.Pp
130For
131.Fn kvm_readstr
132.Dv NULL
133is returned on failure.
134Upon success, the address of the string is returned, which will be
135.Fa buf
136if this was supplied.
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137.Sh SEE ALSO
138.Xr kvm 3 ,
139.Xr kvm_close 3 ,
140.Xr kvm_getargv 3 ,
141.Xr kvm_getenvv 3 ,
142.Xr kvm_geterr 3 ,
143.Xr kvm_getprocs 3 ,
144.Xr kvm_nlist 3 ,
145.Xr kvm_open 3 ,
146.Xr kvm_openfiles 3