Table of 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.
On successful completion, unw_get_reg()
returns 0.
Otherwise the negative value of one of the error-codes below is
returned.
unw_get_reg()
is thread-safe as well as safe to use
from a signal handler.
- 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_create_addr_space(3)).
libunwind(3),
libunwind-ia64(3),
unw_get_fpreg(3),
unw_is_signal_frame(3),
unw_set_reg(3)
David Mosberger-Tang
Hewlett-Packard Labs
Palo-Alto, CA 94304
Email: davidm@hpl.hp.com
WWW: http://www.hpl.hp.com/research/linux/libunwind/.
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