51 lines
1.5 KiB
C++
51 lines
1.5 KiB
C++
#include <libreborn/libreborn.h>
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#include "patch-internal.h"
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// Generate A BL Instruction
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#define INSTRUCTION_RANGE 32000000
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static uint64_t nice_diff_64(uint64_t a, uint64_t b) {
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if (a > b) {
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return a - b;
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} else {
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return b - a;
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}
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}
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uint32_t generate_bl_instruction(void *from, void *to, int use_b_instruction) {
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// Check Instruction Range
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if (nice_diff_64((uint64_t) to, (uint64_t) from) > INSTRUCTION_RANGE) {
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IMPOSSIBLE();
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}
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// Create New Instruction
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uint32_t instruction;
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unsigned char *instruction_array = (unsigned char *) &instruction;
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instruction_array[3] = use_b_instruction ? B_INSTRUCTION : BL_INSTRUCTION;
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// Determine PC
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unsigned char *pc = ((unsigned char *) from) + 8;
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int32_t offset = (int32_t) to - (int32_t) pc;
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int32_t target = offset >> 2;
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// Set Instruction Offset
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unsigned char *target_array = (unsigned char *) ⌖
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instruction_array[0] = target_array[0];
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instruction_array[1] = target_array[1];
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instruction_array[2] = target_array[2];
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// Return
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return instruction;
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}
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// Extract Target Address From B(L) Instruction
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void *extract_from_bl_instruction(unsigned char *from) {
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// Calculate PC
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unsigned char *pc = ((unsigned char *) from) + 8;
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// Extract Offset From Instruction
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int32_t target = *(int32_t *) from;
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target = (target << 8) >> 8;
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int32_t offset = target << 2;
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// Add PC To Offset
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return (void *) (pc + offset);
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}
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