Linux Kernel Architecture

Mauerer runapp01.tex V1 - 09/04/2008 6:08pm Page 1131

Appendix A: Architecture Specifics

unsigned long r12;

unsigned long r13;

unsigned long r14;

unsigned long r15;

unsigned long r26;

unsigned long fp[32]; /* fp[31] is fpcr */

};

The kernel defines the following structure to identify the position of the individual registers on the stack:

arch/alpha/kernel/ptrace.c

#define PT_REG(reg) \

(PAGE_SIZE*2 - sizeof(struct pt_regs) + offsetof(struct pt_regs, reg))

#define SW_REG(reg) \

(PAGE_SIZE*2 - sizeof(struct pt_regs) - sizeof(struct switch_stack) \

+ offsetof(struct switch_stack, reg))

static int regoff[] = {

PT_REG( r0), PT_REG( r1), PT_REG( r2), PT_REG( r3),

PT_REG( r4), PT_REG( r5), PT_REG( r6), PT_REG( r7),

PT_REG( r8), SW_REG( r9), SW_REG( r10), SW_REG( r11),

SW_REG( r12), SW_REG( r13), SW_REG( r14), SW_REG( r15),

PT_REG( r16), PT_REG( r17), PT_REG( r18), PT_REG( r19),

PT_REG( r20), PT_REG( r21), PT_REG( r22), PT_REG( r23),

PT_REG( r24), PT_REG( r25), PT_REG( r26), PT_REG( r27),

PT_REG( r28), PT_REG( gp), -1, -1,

SW_REG(fp[ 0]), SW_REG(fp[ 1]), SW_REG(fp[ 2]), SW_REG(fp[ 3]),

SW_REG(fp[ 4]), SW_REG(fp[ 5]), SW_REG(fp[ 6]), SW_REG(fp[ 7]),

SW_REG(fp[ 8]), SW_REG(fp[ 9]), SW_REG(fp[10]), SW_REG(fp[11]),

SW_REG(fp[12]), SW_REG(fp[13]), SW_REG(fp[14]), SW_REG(fp[15]),

SW_REG(fp[16]), SW_REG(fp[17]), SW_REG(fp[18]), SW_REG(fp[19]),

SW_REG(fp[20]), SW_REG(fp[21]), SW_REG(fp[22]), SW_REG(fp[23]),

SW_REG(fp[24]), SW_REG(fp[25]), SW_REG(fp[26]), SW_REG(fp[27]),

SW_REG(fp[28]), SW_REG(fp[29]), SW_REG(fp[30]), SW_REG(fp[31]),

PT_REG( pc)

};

A.7.6 Mips

Mips processors use an array entry inpt_regsto store the main processor registers, as shown in the

following code. The 32-bit and 64-bit versions of the processor use practically the same structure:

include/asm-mips/ptrace.h

struct pt_regs {

#ifdef CONFIG_32BIT

/* Pad bytes for argument save space on the stack. */

unsigned long pad0[6];

#endif

/* Saved main processor registers. */

unsigned long regs[32];

/* Saved special registers. */