unw_resume(3) [debian man page]

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)

Check Out this Related Man Page

UNW_GET_REG(3)						       Programming Library						    UNW_GET_REG(3)

NAME

       unw_get_reg -- get register contents

SYNOPSIS

       #include <libunwind.h>

       int unw_get_reg(unw_cursor_t *cp, unw_regnum_t reg, unw_word_t *valp);

DESCRIPTION

       The  unw_get_reg()  routine  reads  the	value  of register reg in the stack frame identified by cursor cp and stores the value in the word
       pointed to by valp.

       The register numbering is target-dependent and described in separate manual pages (e.g., libunwind-ia64(3) for the IA-64 target).  Further-
       more,  the exact set of accessible registers may depend on the type of frame that cp is referring to. For ordinary stack frames, it is nor-
       mally possible to access only the preserved (``callee-saved'') registers and frame-related registers (such as the stack-pointer).  However,
       for signal frames (see unw_is_signal_frame(3)), it is usually possible to access all registers.

       Note  that  unw_get_reg() can only read the contents of registers whose values fit in a single word. See unw_get_fpreg(3) for a way to read
       registers which do not fit this constraint.

RETURN VALUE

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

THREAD AND SIGNAL SAFETY

       unw_get_reg() is thread-safe as well as safe to use from a signal handler.

ERRORS

       UNW_EUNSPEC
	       An unspecified error occurred.

       UNW_EBADREG
	       An attempt was made to read a register that is either invalid or not accessible in the current frame.

       In addition, unw_get_reg() may return any error returned by the access_mem(), access_reg(), and	access_fpreg()	call-backs  (see  unw_cre-
       ate_addr_space(3)).

SEE ALSO

       libunwind(3), libunwind-ia64(3), unw_get_fpreg(3), unw_is_signal_frame(3), unw_set_reg(3)

AUTHOR

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

Programming Library						  16 August 2007						    UNW_GET_REG(3)

Linux and UNIX Man Pages

unw_resume(3) [debian man page]

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