88 lines
2.4 KiB
C
88 lines
2.4 KiB
C
#include <exports.h>
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#if defined(CONFIG_I386)
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/*
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* x86 does not have a dedicated register to store the pointer to
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* the global_data. Thus the jump table address is stored in a
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* global variable, but such approach does not allow for execution
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* from flash memory. The global_data address is passed as argv[-1]
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* to the application program.
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*/
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static void **jt;
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#define EXPORT_FUNC(x) \
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asm volatile ( \
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" .globl " #x "\n" \
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#x ":\n" \
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" movl %0, %%eax\n" \
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" movl jt, %%ecx\n" \
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" jmp *(%%ecx, %%eax)\n" \
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: : "i"(XF_ ## x * sizeof(void *)) : "eax", "ecx");
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#elif defined(CONFIG_PPC)
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/*
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* r29 holds the pointer to the global_data, r11 is a call-clobbered
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* register
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*/
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#define EXPORT_FUNC(x) \
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asm volatile ( \
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" .globl " #x "\n" \
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#x ":\n" \
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" lwz %%r11, %0(%%r29)\n" \
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" lwz %%r11, %1(%%r11)\n" \
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" mtctr %%r11\n" \
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" bctr\n" \
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: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r11");
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#elif defined(CONFIG_ARM)
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/*
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* r8 holds the pointer to the global_data, ip is a call-clobbered
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* register
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*/
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#define EXPORT_FUNC(x) \
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asm volatile ( \
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" .globl " #x "\n" \
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#x ":\n" \
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" ldr ip, [r8, %0]\n" \
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" ldr pc, [ip, %1]\n" \
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: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "ip");
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#elif defined(CONFIG_MIPS)
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/*
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* k0 ($26) holds the pointer to the global_data; t9 ($25) is a call-
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* clobbered register that is also used to set gp ($26). Note that the
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* jr instruction also executes the instruction immediately following
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* it; however, GCC/mips generates an additional `nop' after each asm
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* statement
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*/
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#define EXPORT_FUNC(x) \
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asm volatile ( \
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" .globl " #x "\n" \
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#x ":\n" \
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" lw $25, %0($26)\n" \
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" lw $25, %1($25)\n" \
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" jr $25\n" \
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: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "t9");
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#else
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#error stubs definition missing for this architecture
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#endif
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/* This function is necessary to prevent the compiler from
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* generating prologue/epilogue, preparing stack frame etc.
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* The stub functions are special, they do not use the stack
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* frame passed to them, but pass it intact to the actual
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* implementation. On the other hand, asm() statements with
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* arguments can be used only inside the functions (gcc limitation)
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*/
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static void __attribute__((unused)) dummy(void)
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{
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#include <_exports.h>
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}
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void app_startup(char **argv)
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{
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#if defined(CONFIG_I386)
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/* x86 does not have a dedicated register for passing global_data */
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jt = ((gd_t *)argv[-1])->jt;
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#endif
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}
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#undef EXPORT_FUNC
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