DCMD_PROC_GETREGSET

Read the given register set.

#include <sys/procfs.h>

#define DCMD_PROC_GETREGSET  __DIOTF(_DCMD_PROC, __PROC_SUBCMD_PROCFS + 25, procfs_regset)

The arguments to devctl() are:

The argument is a pointer to a procfs_regset structure where the required information can be stored:

typedef struct _procfs_regset {
    uint32_t  id;
    char      buf[8192];
} procfs_regset;

Set the id member to indicate the registers you want to get:

REGSET_ALTREGS

Alternate registers. You can also get and set these registers with the DCMD_PROC_GETALTREG and DCMD_PROC_SETALTREG commands.

REGSET_FPREGS

Floating Point Data registers. You can also get and set these registers with the DCMD_PROC_GETFPREG and DCMD_PROC_SETFPREG commands.

REGSET_GPREGS

CPU registers. You can also get and set these registers with the DCMD_PROC_GETGREG and DCMD_PROC_SETGREG commands.

REGSET_PERFREGS

Performance registers.

For example:

procfs_regset regset;
int           returned_length;

regset.id = REGSET_PERFREGS;
devctl( fd, DCMD_PROC_GETREGSET, &regset, sizeof(regset), &returned_length );

The register sets defined in <sys/debug.h> include some special values, REGSET_STARTCPU and REGSET_STARTPRIV:

• The range from REGSET_STARTCPU up to but not including REGSET_STARTPRIV is for CPU-specific registers.
• The range from REGSET_STARTPRIV and up is for privileged registers.
• The range from REGSET_STARTPRIV + REGSET_STARTCPU and up is for privileged CPU-specific registers.

In order to get or set registers in the range from REGSET_STARTPRIV and up, your process needs the PROCMGR_AID_PRIVREG ability enabled. See procmgr_ability() in the C Library Reference.

The target-specific registers include the following:

AARCH64_REGSET_ACTLR

(AArch 64 targets only) Auxiliary Control Register, a privileged 64-bit register that provides implementation-defined configuration and control options for execution at EL1 and EL0.

Note:

In order for you to use this register, your startup program needs to set the AARCH64_CPU_ACTLR flag in cpuinfo.flags in the system page. For more information, see the System Page chapter of Building Embedded Systems.

For example:

procfs_regset regset;
int           returned_length;

regset.id = AARCH64_REGSET_ACTLR;
*(uint64_t *)&regset.buf[0] = 0;

devctl( fd, DCMD_PROC_GETREGSET, &regset, sizeof(uint32_t) + sizeof(uint64_t),
        &returned_length );
printf ("The value is %llx.\n", *(uint64_t *)&regset.buf[0]);

To set a given register set, use DCMD_PROC_SETREGSET.