examples/stubs.c

   1 #include <exports.h>
   2
   3 #ifndef GCC_VERSION
   4 #define GCC_VERSION (__GNUC__ * 1000 + __GNUC_MINOR__)
   5 #endif /* GCC_VERSION */
   6
   7 #if defined(CONFIG_I386)
   8 /*
   9  * x86 does not have a dedicated register to store the pointer to
  10  * the global_data. Thus the jump table address is stored in a
  11  * global variable, but such approach does not allow for execution
  12  * from flash memory. The global_data address is passed as argv[-1]
  13  * to the application program.
  14  */
  15 static void **jt;
  16 gd_t *global_data;
  17
  18 #define EXPORT_FUNC(x) \
  19         asm volatile (                  \
  20 "       .globl " #x "\n"                \
  21 #x ":\n"                                \
  22 "       movl    %0, %%eax\n"            \
  23 "       movl    jt, %%ecx\n"            \
  24 "       jmp     *(%%ecx, %%eax)\n"      \
  25         : : "i"(XF_ ## x * sizeof(void *)) : "eax", "ecx");
  26 #elif defined(CONFIG_PPC)
  27 /*
  28  * r29 holds the pointer to the global_data, r11 is a call-clobbered
  29  * register
  30  */
  31 #define EXPORT_FUNC(x) \
  32         asm volatile (                  \
  33 "       .globl " #x "\n"                \
  34 #x ":\n"                                \
  35 "       lwz     %%r11, %0(%%r29)\n"     \
  36 "       lwz     %%r11, %1(%%r11)\n"     \
  37 "       mtctr   %%r11\n"                \
  38 "       bctr\n"                         \
  39         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r11");
  40 #elif defined(CONFIG_ARM)
  41 /*
  42  * r8 holds the pointer to the global_data, ip is a call-clobbered
  43  * register
  44  */
  45 #define EXPORT_FUNC(x) \
  46         asm volatile (                  \
  47 "       .globl " #x "\n"                \
  48 #x ":\n"                                \
  49 "       ldr     ip, [r8, %0]\n"         \
  50 "       ldr     pc, [ip, %1]\n"         \
  51         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "ip");
  52 #elif defined(CONFIG_MIPS)
  53 /*
  54  * k0 ($26) holds the pointer to the global_data; t9 ($25) is a call-
  55  * clobbered register that is also used to set gp ($26). Note that the
  56  * jr instruction also executes the instruction immediately following
  57  * it; however, GCC/mips generates an additional `nop' after each asm
  58  * statement
  59  */
  60 #define EXPORT_FUNC(x) \
  61         asm volatile (                  \
  62 "       .globl " #x "\n"                \
  63 #x ":\n"                                \
  64 "       lw      $25, %0($26)\n"         \
  65 "       lw      $25, %1($25)\n"         \
  66 "       jr      $25\n"                  \
  67         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "t9");
  68 #elif defined(CONFIG_NIOS)
  69 /*
  70  * %g7 holds the pointer to the global_data. %g0 is call clobbered.
  71  */
  72 #define EXPORT_FUNC(x) \
  73         asm volatile (                  \
  74 "       .globl " #x "\n"                \
  75 #x ":\n"                                \
  76 "       pfx     %%hi(%0)\n"             \
  77 "       movi    %%g0, %%lo(%0)\n"       \
  78 "       add     %%g0, %%g7\n"           \
  79 "       ld      %%g0, [%%g0]\n"         \
  80 "       pfx     %1\n"                   \
  81 "       ld      %%g0, [%%g0]\n"         \
  82 "       jmp     %%g0\n"                 \
  83 "       nop     \n"                     \
  84         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x) : "r0");
  85 #elif defined(CONFIG_NIOS2)
  86 /*
  87  * r15 holds the pointer to the global_data, r8 is call-clobbered
  88  */
  89 #define EXPORT_FUNC(x) \
  90         asm volatile (                  \
  91 "       .globl " #x "\n"                \
  92 #x ":\n"                                \
  93 "       movhi   r8, %%hi(%0)\n"         \
  94 "       ori     r8, r0, %%lo(%0)\n"     \
  95 "       add     r8, r8, r15\n"          \
  96 "       ldw     r8, 0(r8)\n"            \
  97 "       ldw     r8, %1(r8)\n"           \
  98 "       jmp     r8\n"                   \
  99         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r15");
 100 #elif defined(CONFIG_M68K)
 101 /*
 102  * d7 holds the pointer to the global_data, a0 is a call-clobbered
 103  * register
 104  */
 105 #define EXPORT_FUNC(x) \
 106         asm volatile (                  \
 107 "       .globl " #x "\n"                \
 108 #x ":\n"                                \
 109 "       move.l  %%d7, %%a0\n"           \
 110 "       adda.l  %0, %%a0\n"             \
 111 "       move.l  (%%a0), %%a0\n"         \
 112 "       adda.l  %1, %%a0\n"             \
 113 "       move.l  (%%a0), %%a0\n"         \
 114 "       jmp     (%%a0)\n"                       \
 115         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "a0");
 116 #elif defined(CONFIG_MICROBLAZE)
 117 /*
 118  * r31 holds the pointer to the global_data. r5 is a call-clobbered.
 119  */
 120 #define EXPORT_FUNC(x)                          \
 121         asm volatile (                          \
 122 "       .globl " #x "\n"                        \
 123 #x ":\n"                                        \
 124 "       lwi     r5, r31, %0\n"                  \
 125 "       lwi     r5, r5, %1\n"                   \
 126 "       bra     r5\n"                           \
 127         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r5");
 128 #elif defined(CONFIG_BLACKFIN)
 129 /*
 130  * P5 holds the pointer to the global_data, P0 is a call-clobbered
 131  * register
 132  */
 133 #define EXPORT_FUNC(x)                  \
 134         asm volatile (                  \
 135 "       .globl " #x "\n"                \
 136 #x ":\n"                                \
 137 "       P0 = [P5 + %0]\n"               \
 138 "       P0 = [P0 + %1]\n"               \
 139 "       JUMP (P0)\n"                    \
 140         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "P0");
 141 #elif defined(CONFIG_AVR32)
 142 /*
 143  * r6 holds the pointer to the global_data. r8 is call clobbered.
 144  */
 145 #define EXPORT_FUNC(x)                                  \
 146         asm volatile(                                   \
 147                 "       .globl\t" #x "\n"               \
 148                 #x ":\n"                                \
 149                 "       ld.w    r8, r6[%0]\n"           \
 150                 "       ld.w    pc, r8[%1]\n"           \
 151                 :                                       \
 152                 : "i"(offsetof(gd_t, jt)), "i"(XF_ ##x) \
 153                 : "r8");
 154 #else
 155 #error stubs definition missing for this architecture
 156 #endif
 157
 158 /* This function is necessary to prevent the compiler from
 159  * generating prologue/epilogue, preparing stack frame etc.
 160  * The stub functions are special, they do not use the stack
 161  * frame passed to them, but pass it intact to the actual
 162  * implementation. On the other hand, asm() statements with
 163  * arguments can be used only inside the functions (gcc limitation)
 164  */
 165 #if GCC_VERSION < 3004
 166 static
 167 #endif /* GCC_VERSION */
 168 void __attribute__((unused)) dummy(void)
 169 {
 170 #include <_exports.h>
 171 }
 172
 173 extern unsigned long __bss_start, _end;
 174
 175 void app_startup(char **argv)
 176 {
 177         unsigned long * cp = &__bss_start;
 178
 179         /* Zero out BSS */
 180         while (cp < &_end) {
 181                 *cp++ = 0;
 182         }
 183
 184 #if defined(CONFIG_I386)
 185         /* x86 does not have a dedicated register for passing global_data */
 186         global_data = (gd_t *)argv[-1];
 187         jt = global_data->jt;
 188 #endif
 189 }
 190
 191 #undef EXPORT_FUNC