unw_init_remote(3) [debian man page]

UNW_INIT_REMOTE(3)					       Programming Library						UNW_INIT_REMOTE(3)

NAME

       unw_init_remote -- initialize cursor for remote unwinding

SYNOPSIS

       #include <libunwind.h>

       int unw_init_remote(unw_cursor_t *c, unw_addr_space_t as, void *arg);

DESCRIPTION

       The  unw_init_remote()  routine	initializes the unwind cursor pointed to by c for unwinding in the address space identified by as.  The as
       argument can either be set to unw_local_addr_space  (local  address  space)  or	to  an	arbitrary  address  space  created  with  unw_cre-
       ate_addr_space().

       The  arg  void-pointer tells the address space exactly what entity should be unwound. For example, if unw_local_addr_space is passed in as,
       then arg needs to be a pointer to a context structure containing the machine-state of the initial stack frame.  However, other address-spa-
       ces  may  instead  expect  a  process-id,  a thread-id, or a pointer to an arbitrary structure which identifies the stack-frame chain to be
       unwound. In other words, the interpretation of arg is entirely dependent on the address-space in use; libunwind never interprets the  argu-
       ment in any way on its own.

       Note  that  unw_init_remote() can be used to initiate unwinding in any process, including the local process in which the unwinder itself is
       running. However, for local unwinding, it is generally preferable to use unw_init_local() instead, because it is easier to use and  because
       it may perform better.

RETURN VALUE

       On successful completion, unw_init_remote() returns 0.  Otherwise the negative value of one of the error-codes below is returned.

THREAD AND SIGNAL SAFETY

       unw_init_remote()  is thread-safe. If the local address-space is passed in argument as, this routine is also safe to use from a signal han-
       dler.

ERRORS

       UNW_EINVAL
	       unw_init_remote() was called in a version of libunwind which supports local unwinding only (this  normally  happens  when  defining
	      UNW_LOCAL_ONLY before including <libunwind.h> and then calling unw_init_remote()).

       UNW_EUNSPEC
	       An unspecified error occurred.

       UNW_EBADREG
	       A register needed by unw_init_remote() wasn't accessible.

SEE ALSO

       libunwind(3), unw_create_addr_space(3), unw_init_local(3)

AUTHOR

       David Mosberger-Tang
       Email: dmosberger@gmail.com
       WWW: http://www.nongnu.org/libunwind/.

Programming Library						  16 August 2007						UNW_INIT_REMOTE(3)

UNW_RESUME(3)						       Programming Library						     UNW_RESUME(3)

NAME

       unw_resume -- resume execution in a particular stack frame

SYNOPSIS

       #include <libunwind.h>

       int unw_resume(unw_cursor_t *cp);

DESCRIPTION

       The  unw_resume()  routine  resumes execution at the stack frame identified by cp.  The behavior of this routine differs slightly for local
       and remote unwinding.

       For local unwinding, unw_resume() restores the machine state  and  then	directly  resumes  execution  in  the  target  stack  frame.  Thus
       unw_resume()  does not return in this case. Restoring the machine state normally involves restoring the ``preserved'' (callee-saved) regis-
       ters. However, if execution in any of the stack frames younger (more deeply nested) than the one identified by cp was interrupted by a sig-
       nal,  then unw_resume() will restore all registers as well as the signal mask. Attempting to call unw_resume() on a cursor which identifies
       the stack frame of another thread results in undefined behavior (e.g., the program may crash).

       For remote unwinding, unw_resume() installs the machine state identified by the cursor by calling the access_reg and access_fpreg  accessor
       callbacks as needed. Once that is accomplished, the resume accessor callback is invoked. The unw_resume routine then returns normally (that
       is, unlikely for local unwinding, unw_resume will always return for remote unwinding).

       Most platforms reserve some registers to pass arguments to exception handlers (e.g., IA-64 uses r15-r18 for this purpose). These  registers
       are  normally treated like ``scratch'' registers. However, if libunwind is used to set an exception argument register to a particular value
       (e.g., via unw_set_reg()), then unw_resume() will install this value as the contents of the register. In other words,  the  exception  han-
       dling arguments are installed even in cases where normally only the ``preserved'' registers are restored.

       Note  that unw_resume() does not invoke any unwind handlers (aka, ``personality routines''). If a program needs this, it will have to do so
       on its own by obtaining the unw_proc_info_t of each unwound frame and appropriately processing its  unwind  handler  and  language-specific
       data  area  (lsda).  These  steps  are generally dependent on the target-platform and are regulated by the processor-specific ABI (applica-
       tion-binary interface).

RETURN VALUE

       For local unwinding, unw_resume() does not return on success.  For remote unwinding, it returns 0 on  success.  On  failure,  the  negative
       value of one of the errors below is returned.

THREAD AND SIGNAL SAFETY

       unw_resume() is thread-safe. If cursor cp is in the local address-space, this routine is also safe to use from a signal handler.

ERRORS

       UNW_EUNSPEC
	       An unspecified error occurred.

       UNW_EBADREG
	       A register needed by unw_resume() wasn't accessible.

       UNW_EINVALIDIP
	       The instruction pointer identified by cp is not valid.

       UNW_BADFRAME
	       The stack frame identified by cp is not valid.

SEE ALSO

       libunwind(3), unw_set_reg(3), sigprocmask(2)

AUTHOR

       David Mosberger-Tang
       Email: dmosberger@gmail.com
       WWW: http://www.nongnu.org/libunwind/.

Programming Library						  16 August 2007						     UNW_RESUME(3)