qemu学习（二）————qemu中对处理器大小端的设置

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/****************************************************************************** * Copyright (c) 2011 IBM Corporation * All rights reserved. * This program and the accompanying materials * are made available under the terms of the BSD License * which accompanies this distribution, and is available at * http://www.opensource.org/licenses/bsd-license.php * * Contributors: *     IBM Corporation - initial implementation *****************************************************************************//* * Common byteorder (endianess) macros */#ifndef BYTEORDER_H#define BYTEORDER_Hstatic inline uint16_tbswap_16 (uint16_t x){    return ((x&0xff00) >> 8) | ((x&0xff) << 8);}static inline uint32_tbswap_32 (uint32_t x){    return bswap_16(x >> 16) | (bswap_16(x) << 16);}static inline uint64_tbswap_64 (uint64_t x){    return (uint64_t) bswap_32(x >> 32) | (uint64_t) bswap_32(x) << 32;}/* gcc defines __BIG_ENDIAN__ on big endian targets */#ifdef __BIG_ENDIAN__#define cpu_to_be16(x) (x)#define cpu_to_be32(x) (x)#define cpu_to_be64(x) (x)#define be16_to_cpu(x) (x)#define be32_to_cpu(x) (x)#define be64_to_cpu(x) (x)#define le16_to_cpu(x) bswap_16(x)#define le32_to_cpu(x) bswap_32(x)#define le64_to_cpu(x) bswap_64(x)#define cpu_to_le16(x) bswap_16(x)#define cpu_to_le32(x) bswap_32(x)#define cpu_to_le64(x) bswap_64(x)#else#define cpu_to_be16(x) bswap_16(x)#define cpu_to_be32(x) bswap_32(x)#define cpu_to_be64(x) bswap_64(x)#define be16_to_cpu(x) bswap_16(x)#define be32_to_cpu(x) bswap_32(x)#define be64_to_cpu(x) bswap_64(x)#define le16_to_cpu(x) (x)#define le32_to_cpu(x) (x)#define le64_to_cpu(x) (x)#define cpu_to_le16(x) (x)#define cpu_to_le32(x) (x)#define cpu_to_le64(x) (x)#endif  /* __BIG_ENDIAN__ */#endif  /* BYTEORDER_H */

上面的code存在于./roms/SLOF/include/byteorder.h中，用来控制字节顺序。

下面的三个函数，通过移位用算实现了16、32、64位整数的高低两部分的转换。（这里有个疑问，大小端是按照字节来布局的，还是按照整型数位数的一半？？？？）

static inline uint16_tbswap_16 (uint16_t x){    return ((x&0xff00) >> 8) | ((x&0xff) << 8);}static inline uint32_tbswap_32 (uint32_t x){    return bswap_16(x >> 16) | (bswap_16(x) << 16);}static inline uint64_tbswap_64 (uint64_t x){    return (uint64_t) bswap_32(x >> 32) | (uint64_t) bswap_32(x) << 32;}

通过宏#ifdef __BIG_ENDIAN__来选择大端和小端。

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前面提到了./roms/SLOF/include/byteorder.h里的字节序列，也提出了疑问。下面加入./include/qemu/bswap.h处关于大小端的定义（注意宏定义的if 和 else）：

#ifndef BSWAP_H#define BSWAP_H#include "config-host.h"#include <inttypes.h>#include <limits.h>#include "fpu/softfloat.h"#ifdef CONFIG_MACHINE_BSWAP_H# include <sys/endian.h># include <sys/types.h># include <machine/bswap.h>#elif defined(CONFIG_BYTESWAP_H)# include <byteswap.h>static inline uint16_t bswap16(uint16_t x){    return bswap_16(x);}static inline uint32_t bswap32(uint32_t x){    return bswap_32(x);}static inline uint64_t bswap64(uint64_t x){    return bswap_64(x);}# elsestatic inline uint16_t bswap16(uint16_t x){    return (((x & 0x00ff) << 8) |            ((x & 0xff00) >> 8));}static inline uint32_t bswap32(uint32_t x){    return (((x & 0x000000ffU) << 24) |            ((x & 0x0000ff00U) <<  8) |            ((x & 0x00ff0000U) >>  8) |            ((x & 0xff000000U) >> 24));}static inline uint64_t bswap64(uint64_t x){    return (((x & 0x00000000000000ffULL) << 56) |            ((x & 0x000000000000ff00ULL) << 40) |            ((x & 0x0000000000ff0000ULL) << 24) |            ((x & 0x00000000ff000000ULL) <<  8) |            ((x & 0x000000ff00000000ULL) >>  8) |            ((x & 0x0000ff0000000000ULL) >> 24) |            ((x & 0x00ff000000000000ULL) >> 40) |            ((x & 0xff00000000000000ULL) >> 56));}#endif /* ! CONFIG_MACHINE_BSWAP_H */static inline void bswap16s(uint16_t *s){    *s = bswap16(*s);}static inline void bswap32s(uint32_t *s){    *s = bswap32(*s);}static inline void bswap64s(uint64_t *s){    *s = bswap64(*s);}#if defined(HOST_WORDS_BIGENDIAN)#define be_bswap(v, size) (v)#define le_bswap(v, size) glue(bswap, size)(v)#define be_bswaps(v, size)#define le_bswaps(p, size) do { *p = glue(bswap, size)(*p); } while(0)#else#define le_bswap(v, size) (v)#define be_bswap(v, size) glue(bswap, size)(v)#define le_bswaps(v, size)#define be_bswaps(p, size) do { *p = glue(bswap, size)(*p); } while(0)#endif#define CPU_CONVERT(endian, size, type)\static inline type endian ## size ## _to_cpu(type v)\{\    return glue(endian, _bswap)(v, size);\}\\static inline type cpu_to_ ## endian ## size(type v)\{\    return glue(endian, _bswap)(v, size);\}\\static inline void endian ## size ## _to_cpus(type *p)\{\    glue(endian, _bswaps)(p, size);\}\\static inline void cpu_to_ ## endian ## size ## s(type *p)\{\    glue(endian, _bswaps)(p, size);\}\\static inline type endian ## size ## _to_cpup(const type *p)\{\    return glue(glue(endian, size), _to_cpu)(*p);\}\\static inline void cpu_to_ ## endian ## size ## w(type *p, type v)\{\    *p = glue(glue(cpu_to_, endian), size)(v);\}CPU_CONVERT(be, 16, uint16_t)CPU_CONVERT(be, 32, uint32_t)CPU_CONVERT(be, 64, uint64_t)CPU_CONVERT(le, 16, uint16_t)CPU_CONVERT(le, 32, uint32_t)CPU_CONVERT(le, 64, uint64_t)/* len must be one of 1, 2, 4 */static inline uint32_t qemu_bswap_len(uint32_t value, int len){    return bswap32(value) >> (32 - 8 * len);}/* Unions for reinterpreting between floats and integers.  */typedef union {    float32 f;    uint32_t l;} CPU_FloatU;typedef union {    float64 d;#if defined(HOST_WORDS_BIGENDIAN)    struct {        uint32_t upper;        uint32_t lower;    } l;#else    struct {        uint32_t lower;        uint32_t upper;    } l;#endif    uint64_t ll;} CPU_DoubleU;typedef union {     floatx80 d;     struct {         uint64_t lower;         uint16_t upper;     } l;} CPU_LDoubleU;typedef union {    float128 q;#if defined(HOST_WORDS_BIGENDIAN)    struct {        uint32_t upmost;        uint32_t upper;        uint32_t lower;        uint32_t lowest;    } l;    struct {        uint64_t upper;        uint64_t lower;    } ll;#else    struct {        uint32_t lowest;        uint32_t lower;        uint32_t upper;        uint32_t upmost;    } l;    struct {        uint64_t lower;        uint64_t upper;    } ll;#endif} CPU_QuadU;/* unaligned/endian-independent pointer access *//* * the generic syntax is: * * load: ld{type}{sign}{size}{endian}_p(ptr) * * store: st{type}{size}{endian}_p(ptr, val) * * Note there are small differences with the softmmu access API! * * type is: * (empty): integer access *   f    : float access * * sign is: * (empty): for floats or 32 bit size *   u    : unsigned *   s    : signed * * size is: *   b: 8 bits *   w: 16 bits *   l: 32 bits *   q: 64 bits * * endian is: * (empty): host endian *   be   : big endian *   le   : little endian */static inline int ldub_p(const void *ptr){    return *(uint8_t *)ptr;}static inline int ldsb_p(const void *ptr){    return *(int8_t *)ptr;}static inline void stb_p(void *ptr, int v){    *(uint8_t *)ptr = v;}/* Any compiler worth its salt will turn these memcpy into native unaligned   operations.  Thus we don't need to play games with packed attributes, or   inline byte-by-byte stores.  */static inline int lduw_p(const void *ptr){    uint16_t r;    memcpy(&r, ptr, sizeof(r));    return r;}static inline int ldsw_p(const void *ptr){    int16_t r;    memcpy(&r, ptr, sizeof(r));    return r;}static inline void stw_p(void *ptr, uint16_t v){    memcpy(ptr, &v, sizeof(v));}static inline int ldl_p(const void *ptr){    int32_t r;    memcpy(&r, ptr, sizeof(r));    return r;}static inline void stl_p(void *ptr, uint32_t v){    memcpy(ptr, &v, sizeof(v));}static inline uint64_t ldq_p(const void *ptr){    uint64_t r;    memcpy(&r, ptr, sizeof(r));    return r;}static inline void stq_p(void *ptr, uint64_t v){    memcpy(ptr, &v, sizeof(v));}static inline int lduw_le_p(const void *ptr){    return (uint16_t)le_bswap(lduw_p(ptr), 16);}static inline int ldsw_le_p(const void *ptr){    return (int16_t)le_bswap(lduw_p(ptr), 16);}static inline int ldl_le_p(const void *ptr){    return le_bswap(ldl_p(ptr), 32);}static inline uint64_t ldq_le_p(const void *ptr){    return le_bswap(ldq_p(ptr), 64);}static inline void stw_le_p(void *ptr, int v){    stw_p(ptr, le_bswap(v, 16));}static inline void stl_le_p(void *ptr, int v){    stl_p(ptr, le_bswap(v, 32));}static inline void stq_le_p(void *ptr, uint64_t v){    stq_p(ptr, le_bswap(v, 64));}/* float access */static inline float32 ldfl_le_p(const void *ptr){    CPU_FloatU u;    u.l = ldl_le_p(ptr);    return u.f;}static inline void stfl_le_p(void *ptr, float32 v){    CPU_FloatU u;    u.f = v;    stl_le_p(ptr, u.l);}static inline float64 ldfq_le_p(const void *ptr){    CPU_DoubleU u;    u.ll = ldq_le_p(ptr);    return u.d;}static inline void stfq_le_p(void *ptr, float64 v){    CPU_DoubleU u;    u.d = v;    stq_le_p(ptr, u.ll);}static inline int lduw_be_p(const void *ptr){    return (uint16_t)be_bswap(lduw_p(ptr), 16);}static inline int ldsw_be_p(const void *ptr){    return (int16_t)be_bswap(lduw_p(ptr), 16);}static inline int ldl_be_p(const void *ptr){    return be_bswap(ldl_p(ptr), 32);}static inline uint64_t ldq_be_p(const void *ptr){    return be_bswap(ldq_p(ptr), 64);}static inline void stw_be_p(void *ptr, int v){    stw_p(ptr, be_bswap(v, 16));}static inline void stl_be_p(void *ptr, int v){    stl_p(ptr, be_bswap(v, 32));}static inline void stq_be_p(void *ptr, uint64_t v){    stq_p(ptr, be_bswap(v, 64));}/* float access */static inline float32 ldfl_be_p(const void *ptr){    CPU_FloatU u;    u.l = ldl_be_p(ptr);    return u.f;}static inline void stfl_be_p(void *ptr, float32 v){    CPU_FloatU u;    u.f = v;    stl_be_p(ptr, u.l);}static inline float64 ldfq_be_p(const void *ptr){    CPU_DoubleU u;    u.ll = ldq_be_p(ptr);    return u.d;}static inline void stfq_be_p(void *ptr, float64 v){    CPU_DoubleU u;    u.d = v;    stq_be_p(ptr, u.ll);}/* Legacy unaligned versions.  Note that we never had a complete set.  */static inline void cpu_to_le16wu(uint16_t *p, uint16_t v){    stw_le_p(p, v);}static inline void cpu_to_le32wu(uint32_t *p, uint32_t v){    stl_le_p(p, v);}static inline uint16_t le16_to_cpupu(const uint16_t *p){    return lduw_le_p(p);}static inline uint32_t le32_to_cpupu(const uint32_t *p){    return ldl_le_p(p);}static inline uint32_t be32_to_cpupu(const uint32_t *p){    return ldl_be_p(p);}static inline void cpu_to_be16wu(uint16_t *p, uint16_t v){    stw_be_p(p, v);}static inline void cpu_to_be32wu(uint32_t *p, uint32_t v){    stl_be_p(p, v);}static inline void cpu_to_be64wu(uint64_t *p, uint64_t v){    stq_be_p(p, v);}static inline void cpu_to_32wu(uint32_t *p, uint32_t v){    stl_p(p, v);}static inline unsigned long leul_to_cpu(unsigned long v){    /* In order to break an include loop between here and       qemu-common.h, don't rely on HOST_LONG_BITS.  */#if ULONG_MAX == UINT32_MAX    return le_bswap(v, 32);#elif ULONG_MAX == UINT64_MAX    return le_bswap(v, 64);#else# error Unknown sizeof long#endif}#undef le_bswap#undef be_bswap#undef le_bswaps#undef be_bswaps#endif /* BSWAP_H */