Get the information stored in the alternate register set for the process associated with the file descriptor.

#include <sys/procfs.h>


The arguments to devctl() are:

Argument Value
filedes A file descriptor for the process.
dev_data_ptr A pointer to a procfs_fpreg structure
n_bytes sizeof(procfs_fpreg)
dev_info_ptr NULL, or a pointer to an integer where the size of the register set can be stored

The argument is a pointer to a procfs_fpreg structure (see debug_fpreg_t in <sys/debug.h>) that's filled in with the required information on return. If you provide a non-NULL extra argument, it's filled with the actual size of the register set. For example:

procfs_fpreg reg;
int regsize;

devctl( fd, DCMD_PROC_GETALTREG, &reg, sizeof(reg), &regsize);
Note: If the thread hasn't used the alternate register set (e.g., AltiVec registers), the read may fail.

To set the alternate register set, use DCMD_PROC_SETALTREG.