examples/standalone/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  * r2 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(%%r2)\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_NIOS2)
  69 /*
  70  * gp holds the pointer to the global_data, r8 is call-clobbered
  71  */
  72 #define EXPORT_FUNC(x) \
  73         asm volatile (                  \
  74 "       .globl " #x "\n"                \
  75 #x ":\n"                                \
  76 "       movhi   r8, %%hi(%0)\n"         \
  77 "       ori     r8, r0, %%lo(%0)\n"     \
  78 "       add     r8, r8, gp\n"           \
  79 "       ldw     r8, 0(r8)\n"            \
  80 "       ldw     r8, %1(r8)\n"           \
  81 "       jmp     r8\n"                   \
  82         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "gp");
  83 #elif defined(CONFIG_M68K)
  84 /*
  85  * d7 holds the pointer to the global_data, a0 is a call-clobbered
  86  * register
  87  */
  88 #define EXPORT_FUNC(x) \
  89         asm volatile (                  \
  90 "       .globl " #x "\n"                \
  91 #x ":\n"                                \
  92 "       move.l  %%d7, %%a0\n"           \
  93 "       adda.l  %0, %%a0\n"             \
  94 "       move.l  (%%a0), %%a0\n"         \
  95 "       adda.l  %1, %%a0\n"             \
  96 "       move.l  (%%a0), %%a0\n"         \
  97 "       jmp     (%%a0)\n"                       \
  98         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "a0");
  99 #elif defined(CONFIG_MICROBLAZE)
 100 /*
 101  * r31 holds the pointer to the global_data. r5 is a call-clobbered.
 102  */
 103 #define EXPORT_FUNC(x)                          \
 104         asm volatile (                          \
 105 "       .globl " #x "\n"                        \
 106 #x ":\n"                                        \
 107 "       lwi     r5, r31, %0\n"                  \
 108 "       lwi     r5, r5, %1\n"                   \
 109 "       bra     r5\n"                           \
 110         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r5");
 111 #elif defined(CONFIG_BLACKFIN)
 112 /*
 113  * P3 holds the pointer to the global_data, P0 is a call-clobbered
 114  * register
 115  */
 116 #define EXPORT_FUNC(x)                  \
 117         asm volatile (                  \
 118 "       .globl _" #x "\n_"              \
 119 #x ":\n"                                \
 120 "       P0 = [P3 + %0]\n"               \
 121 "       P0 = [P0 + %1]\n"               \
 122 "       JUMP (P0)\n"                    \
 123         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "P0");
 124 #elif defined(CONFIG_AVR32)
 125 /*
 126  * r6 holds the pointer to the global_data. r8 is call clobbered.
 127  */
 128 #define EXPORT_FUNC(x)                                  \
 129         asm volatile(                                   \
 130                 "       .globl\t" #x "\n"               \
 131                 #x ":\n"                                \
 132                 "       ld.w    r8, r6[%0]\n"           \
 133                 "       ld.w    pc, r8[%1]\n"           \
 134                 :                                       \
 135                 : "i"(offsetof(gd_t, jt)), "i"(XF_ ##x) \
 136                 : "r8");
 137 #elif defined(CONFIG_SH)
 138 /*
 139  * r13 holds the pointer to the global_data. r1 is a call clobbered.
 140  */
 141 #define EXPORT_FUNC(x)                                  \
 142         asm volatile (                                  \
 143                 "       .align  2\n"                    \
 144                 "       .globl " #x "\n"                \
 145                 #x ":\n"                                \
 146                 "       mov     r13, r1\n"              \
 147                 "       add     %0, r1\n"               \
 148                 "       mov.l @r1, r2\n"        \
 149                 "       add     %1, r2\n"               \
 150                 "       mov.l @r2, r1\n"        \
 151                 "       jmp     @r1\n"                  \
 152                 "       nop\n"                          \
 153                 "       nop\n"                          \
 154                 : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r1", "r2");
 155 #elif defined(CONFIG_SPARC)
 156 /*
 157  * g7 holds the pointer to the global_data. g1 is call clobbered.
 158  */
 159 #define EXPORT_FUNC(x)                                  \
 160         asm volatile(                                   \
 161 "       .globl\t" #x "\n"                               \
 162 #x ":\n"                                                \
 163 "       set %0, %%g1\n"                                 \
 164 "       or %%g1, %%g7, %%g1\n"                          \
 165 "       ld [%%g1], %%g1\n"                              \
 166 "       ld [%%g1 + %1], %%g1\n"                         \
 167 "       jmp %%g1\n"                                     \
 168 "       nop\n"                                          \
 169         : : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "g1" );
 170
 171 #else
 172 #error stubs definition missing for this architecture
 173 #endif
 174
 175 /* This function is necessary to prevent the compiler from
 176  * generating prologue/epilogue, preparing stack frame etc.
 177  * The stub functions are special, they do not use the stack
 178  * frame passed to them, but pass it intact to the actual
 179  * implementation. On the other hand, asm() statements with
 180  * arguments can be used only inside the functions (gcc limitation)
 181  */
 182 #if GCC_VERSION < 3004
 183 static
 184 #endif /* GCC_VERSION */
 185 void __attribute__((unused)) dummy(void)
 186 {
 187 #include <_exports.h>
 188 }
 189
 190 extern unsigned long __bss_start, _end;
 191
 192 void app_startup(char * const *argv)
 193 {
 194         unsigned char * cp = (unsigned char *) &__bss_start;
 195
 196         /* Zero out BSS */
 197         while (cp < (unsigned char *)&_end) {
 198                 *cp++ = 0;
 199         }
 200
 201 #if defined(CONFIG_I386)
 202         /* x86 does not have a dedicated register for passing global_data */
 203         global_data = (gd_t *)argv[-1];
 204         jt = global_data->jt;
 205 #endif
 206 }
 207
 208 #undef EXPORT_FUNC