Linux Kernel Architecture

Mauerer runapp01.tex V1 - 09/04/2008 6:08pm Page 1133

Appendix A: Architecture Specifics

#else

unsigned long mq; /* 601 only (not used at present) */

/* Used on APUS to hold IPL value. */

#endif

unsigned long trap; /* Reason for being here */

/* N.B. for critical exceptions on 4xx, the dar and dsisr

fields are overloaded to hold srr0 and srr1. */

unsigned long dar; /* Fault registers */

unsigned long dsisr; /* on 4xx/Book-E used for ESR */

unsigned long result; /* Result of a system call */

};

Depending on the processor type, it may be necessary to consider whether the AltiVec extension (and
therefore an additional register set) is present when floating-point registers are saved. Debug registers
must also be saved on some system types:

include/asm-powerpc/processor.h

struct thread_struct {

unsigned long ksp; /* Kernel stack pointer */

#ifdef CONFIG_PPC64

unsigned long ksp_vsid;

#endif

struct pt_regs *regs; /* Pointer to saved register state */

mm_segment_t fs; /* for get_fs() validation */

#ifdef CONFIG_PPC32

void *pgdir; /* root of page-table tree */

signed long last_syscall;

#endif

#if defined(CONFIG_4xx) || defined (CONFIG_BOOKE)

unsigned long dbcr0; /* debug control register values */

unsigned long dbcr1;

#endif

double fpr[32]; /* Complete floating point set */

struct { /* fpr ... fpscr must be contiguous */

unsigned int pad;

unsigned int val; /* Floating point status */

} fpscr;

int fpexc_mode; /* floating-point exception mode */

#ifdef CONFIG_PPC64

unsigned long start_tb; /* Start purr when proc switched in */

unsigned long accum_tb; /* Total accumilated purr for process */

#endif

unsigned long vdso_base; /* base of the vDSO library */

unsigned long dabr; /* Data address breakpoint register */

#ifdef CONFIG_ALTIVEC

/* Complete AltiVec register set */

vector128 vr[32] __attribute((aligned(16)));

/* AltiVec status */

vector128 vscr __attribute((aligned(16)));

unsigned long vrsave;

int used_vr; /* set if process has used altivec */

#endif /* CONFIG_ALTIVEC */

};