unw_get_reg - Man Page

get register contents


#include <libunwind.h>

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


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).  Furthermore, the exact set of accessible registers may depend on the  type of frame that cp is referring to. For ordinary stack  frames, it is normally 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.



An unspecified error occurred.


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_create_addr_space(3)).

See Also

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


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

Referenced By

libunwind(3), unw_get_fpreg(3), unw_is_fpreg(3), unw_is_signal_frame(3), unw_set_reg(3).

16 August 2007 Programming Library