libunwind-eh_elf/doc/unw_create_addr_space.man

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.TH "UNW\\_CREATE\\_ADDR\\_SPACE" "3" "20 April 2005" "Programming Library " "Programming Library "
.SH NAME
unw_create_addr_space
\-\- create address space for remote unwinding 
.PP
.SH SYNOPSIS

.PP
#include <libunwind.h>
.br
.PP
unw_addr_space_t
unw_create_addr_space(unw_accessors_t *ap,
int
byteorder);
.br
.PP
.SH DESCRIPTION

.PP
The unw_create_addr_space()
routine creates a new unwind 
address\-space and initializes it based on the call\-back routines 
passed via the ap
pointer and the specified byteorder\&.
The call\-back routines are described in detail below. The 
byteorder
can be set to 0 to request the default byte\-order of 
the unwind target. To request a particular byte\-order, 
byteorder
can be set to any constant defined by 
<endian.h>\&.
In particular, __LITTLE_ENDIAN
would 
request little\-endian byte\-order and __BIG_ENDIAN
would 
request big\-endian byte\-order. Whether or not a particular byte\-order 
is supported depends on the target platform. 
.PP
.SH CALL\-BACK ROUTINES

.PP
Libunwind
uses a set of call\-back routines to access the 
information it needs to unwind a chain of stack\-frames. These 
routines are specified via the ap
argument, which points to a 
variable of type unw_accessors_t\&.
The contents of this 
variable is copied into the newly\-created address space, so the 
variable must remain valid only for the duration of the call to 
unw_create_addr_space().
.PP
The first argument to every call\-back routine is an address\-space 
identifier (as)
and the last argument is an arbitrary, 
application\-specified void\-pointer (arg).
When invoking a 
call\-back routine, libunwind
sets the as
argument to the 
address\-space on whose behalf the invocation is made and the arg
argument to the value that was specified when 
unw_init_remote(3)
was called. 
.PP
The synopsis and a detailed description of every call\-back routine 
follows below. 
.PP
.SS CALL\-BACK ROUTINE SYNOPSIS
.PP
int
find_proc_info(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_word_t
ip,
unw_proc_info_t *pip,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPint
need_unwind_info,
void *arg);
.br
void
put_unwind_info(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_proc_info_t *pip,
void *arg);
.br
int
get_dyn_info_list_addr(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_word_t *dilap,
void *arg);
.br
int
access_mem(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_word_t
addr,
unw_word_t *valp,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPint
write,
void *arg);
.br
int
access_reg(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_regnum_t
regnum,
unw_word_t *valp,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPint
write,
void *arg);
.br
int
access_fpreg(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_regnum_t
regnum,
unw_fpreg_t *fpvalp,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPint
write,
void *arg);
.br
int
resume(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_cursor_t *cp,
void *arg);
.br
int
get_proc_name(unw_addr_space_t
as,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPunw_word_t
addr,
char *bufp,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPsize_t
buf_len,
unw_word_t *offp,
.br
\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fP\fB \fPvoid *arg);
.br
.PP
.SS FIND_PROC_INFO
.PP
Libunwind
invokes the find_proc_info()
call\-back to 
locate the information need to unwind a particular procedure. The 
ip
argument is an instruction\-address inside the procedure whose 
information is needed. The pip
argument is a pointer to the 
variable used to return the desired information. The type of this 
variable is unw_proc_info_t\&.
See 
unw_get_proc_info(3)
for details. Argument 
need_unwind_info
is zero if the call\-back does not need to 
provide values for the following members in the 
unw_proc_info_t
structure: format,
unwind_info_size,
and unwind_info\&.
If 
need_unwind_info
is non\-zero, valid values need to be returned 
in these members. Furthermore, the contents of the memory addressed 
by the unwind_info
member must remain valid until the info is 
released via the put_unwind_info
call\-back (see below). 
.PP
On successful completion, the find_proc_info()
call\-back must 
return zero. Otherwise, the negative value of one of the 
unw_error_t
error\-codes may be returned. In particular, this 
call\-back may return \-UNW_ESTOPUNWIND
to signal the end of 
the frame\-chain. 
.PP
.SS PUT_UNWIND_INFO
.PP
Libunwind
invokes the put_unwind_info()
call\-back to 
release the resources (such as memory) allocated by a previous call to 
find_proc_info()
with the need_unwind_info
argument 
set to a non\-zero value. The pip
argument has the same value as 
the argument of the same name in the previous matching call to 
find_proc_info().
Note that libunwind
does \fInot\fP
invoke put_unwind_info
for calls to find_proc_info()
with a zero need_unwind_info
argument. 
.PP
.SS GET_DYN_INFO_LIST_ADDR
.PP
Libunwind
invokes the get_dyn_info_list_addr()
call\-back to obtain the address of the head of the dynamic unwind\-info 
registration list. The variable stored at the returned address must 
have a type of unw_dyn_info_list_t
(see 
_U_dyn_register(3)).
The dliap
argument is a pointer 
to a variable of type unw_word_t
which is used to return the 
address of the dynamic unwind\-info registration list. If no dynamic 
unwind\-info registration list exist, the value pointed to by 
dliap
must be cleared to zero. Libunwind
will cache the 
value returned by get_dyn_info_list_addr()
if caching is 
enabled for the given address\-space. The cache can be cleared with a 
call to unw_flush_cache().
.PP
On successful completion, the get_dyn_info_list_addr()
call\-back must return zero. Otherwise, the negative value of one of 
the unw_error_t
error\-codes may be returned. 
.PP
.SS ACCESS_MEM
.PP
Libunwind
invokes the access_mem()
call\-back to read 
from or write to a word of memory in the target address\-space. The 
address of the word to be accessed is passed in argument addr\&.
To read memory, libunwind
sets argument write
to zero and 
valp
to point to the word that receives the read value. To 
write memory, libunwind
sets argument write
to a non\-zero 
value and valp
to point to the word that contains the value to 
be written. The word that valp
points to is always in the 
byte\-order of the host\-platform, regardless of the byte\-order of the 
target. In other words, it is the responsibility of the call\-back 
routine to convert between the target\&'s and the host\&'s byte\-order, if 
necessary. 
.PP
On successful completion, the access_mem()
call\-back must return zero. Otherwise, the negative value of one of 
the unw_error_t
error\-codes may be returned. 
.PP
.SS ACCESS_REG
.PP
Libunwind
invokes the access_reg()
call\-back to read 
from or write to a scalar (non\-floating\-point) CPU register. The 
index of the register to be accessed is passed in argument 
regnum\&.
To read a register, libunwind
sets argument 
write
to zero and valp
to point to the word that receives 
the read value. To write a register, libunwind
sets argument 
write
to a non\-zero value and valp
to point to the word 
that contains the value to be written. The word that valp
points to is always in the byte\-order of the host\-platform, regardless 
of the byte\-order of the target. In other words, it is the 
responsibility of the call\-back routine to convert between the 
target\&'s and the host\&'s byte\-order, if necessary. 
.PP
On successful completion, the access_reg()
call\-back must 
return zero. Otherwise, the negative value of one of the 
unw_error_t
error\-codes may be returned. 
.PP
.SS ACCESS_FPREG
.PP
Libunwind
invokes the access_fpreg()
call\-back to read 
from or write to a floating\-point CPU register. The index of the 
register to be accessed is passed in argument regnum\&.
To read a 
register, libunwind
sets argument write
to zero and 
fpvalp
to point to a variable of type unw_fpreg_t
that 
receives the read value. To write a register, libunwind
sets 
argument write
to a non\-zero value and fpvalp
to point to 
the variable of type unw_fpreg_t
that contains the value to 
be written. The word that fpvalp
points to is always in the 
byte\-order of the host\-platform, regardless of the byte\-order of the 
target. In other words, it is the responsibility of the call\-back 
routine to convert between the target\&'s and the host\&'s byte\-order, if 
necessary. 
.PP
On successful completion, the access_fpreg()
call\-back must 
return zero. Otherwise, the negative value of one of the 
unw_error_t
error\-codes may be returned. 
.PP
.SS RESUME
.PP
Libunwind
invokes the resume()
call\-back to resume 
execution in the target address space. Argument cp
is the 
unwind\-cursor that identifies the stack\-frame in which execution 
should resume. By the time libunwind
invokes the resume
call\-back, it has already established the desired machine\- and 
memory\-state via calls to the access_reg(),
access_fpreg,
and access_mem()
call\-backs. Thus, all 
the call\-back needs to do is perform whatever action is needed to 
actually resume execution. 
.PP
The resume
call\-back is invoked only in response to a call to 
unw_resume(3),
so applications which never invoke 
unw_resume(3)
need not define the resume
callback. 
.PP
On successful completion, the resume()
call\-back must return 
zero. Otherwise, the negative value of one of the 
unw_error_t
error\-codes may be returned. As a special case, 
when resuming execution in the local address space, the call\-back will 
not return on success. 
.PP
.SS GET_PROC_NAME
.PP
Libunwind
invokes the get_proc_name()
call\-back to 
obtain the procedure\-name of a static (not dynamically generated) 
procedure. Argument addr
is an instruction\-address within the 
procedure whose name is to be obtained. The bufp
argument is a 
pointer to a character\-buffer used to return the procedure name. The 
size of this buffer is specified in argument buf_len\&.
The 
returned name must be terminated by a NUL character. If the 
procedure\&'s name is longer than buf_len
bytes, it must be 
truncated to buf_len\-1
bytes, with the last byte in the 
buffer set to the NUL character and \-UNW_ENOMEM
must be 
returned. Argument offp
is a pointer to a word which is used to 
return the byte\-offset relative to the start of the procedure whose 
name is being returned. For example, if procedure foo()
starts 
at address 0x40003000, then invoking get_proc_name()
with 
addr
set to 0x40003080 should return a value of 0x80 in the word 
pointed to by offp
(assuming the procedure is at least 0x80 
bytes long). 
.PP
On successful completion, the get_proc_name()
call\-back must 
return zero. Otherwise, the negative value of one of the 
unw_error_t
error\-codes may be returned. 
.PP
.SH RETURN VALUE

.PP
On successful completion, unw_create_addr_space()
returns a 
non\-NULL
value that represents the newly created 
address\-space. Otherwise, NULL
is returned. 
.PP
.SH THREAD AND SIGNAL SAFETY

.PP
unw_create_addr_space()
is thread\-safe but \fInot\fP
safe to use from a signal handler. 
.PP
.SH SEE ALSO

.PP
_U_dyn_register(3),
libunwind(3),
unw_destroy_addr_space(3),
unw_get_proc_info(3),
unw_init_remote(3),
unw_resume(3)
.PP
.SH AUTHOR

.PP
David Mosberger\-Tang
.br 
Hewlett\-Packard Labs
.br 
Palo\-Alto, CA 94304
.br 
Email: \fBdavidm@hpl.hp.com\fP
.br
WWW: \fBhttp://www.hpl.hp.com/research/linux/libunwind/\fP\&.
.\" NOTE: This file is generated, DO NOT EDIT.