Linux Kernel Architecture

Mauerer runapp01.tex V1 - 09/04/2008 6:08pm Page 1132

Appendix A: Architecture Specifics

unsigned long cp0_status;

unsigned long hi;

unsigned long lo;

unsigned long cp0_badvaddr;

unsigned long cp0_cause;

unsigned long cp0_epc;

};

Because Mips processors do not necessarily have a numeric coprocessor, no floating-point registers may

need to be saved — just the status of the software emulation, as shown here:

include/asm-mips/processor.h

struct thread_struct {

/* Saved main processor registers. */

unsigned long reg16;

unsigned long reg17, reg18, reg19, reg20, reg21, reg22, reg23;

unsigned long reg29, reg30, reg31;

/* Saved cp0 stuff. */

unsigned long cp0_status;

/* Saved fpu/fpu emulator stuff. */

union mips_fpu_union fpu;

/* Saved state of the DSP ASE, if available. */

struct mips_dsp_state dsp;

/* Other stuff associated with the thread. */

unsigned long cp0_badvaddr; /* Last user fault */

unsigned long cp0_baduaddr; /* Last kernel fault accessing USEG */

unsigned long error_code;

unsigned long trap_no;

unsigned long mflags;

unsigned long irix_trampoline; /* Wheee... */

unsigned long irix_oldctx;

struct mips_abi *abi;

};

A.7.7 PowerPC

PowerPCs save most registers in an array held inpt_regs:

include/asm-powerpc/ptrace.h

struct pt_regs {

unsigned long gpr[32];

unsigned long nip;

unsigned long msr;

unsigned long orig_gpr3; /* Used for restarting system calls */

unsigned long ctr;

unsigned long link;

unsigned long xer;

unsigned long ccr;

#ifdef __powerpc64__

unsigned long softe; /* Soft enabled/disabled */