style: format arrays
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1 changed files with 62 additions and 62 deletions
124
README.md
124
README.md
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@ -38,27 +38,27 @@ All computation happens inside registers - RAM just holds the data until it’s
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#### Special registers
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| 64-bit | 32-bit | 16-bit | Name | Purpose |
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|--------|--------|--------|------|---------|
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| `rsp` | `esp` | `sp` | Stack Pointer | Points to the top of the stack |
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| `rbp` | `ebp` | `bp` | Base Pointer | Marks the base of the current stack frame |
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| `rip` | `eip` | `ip` | Instruction Pointer | Points to the next instruction to execute |
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| `rflags` | `eflags` | `flags` | Flags Register | Stores CPU state flags (zero, carry, sign, overflow...) |
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| 64-bit | 32-bit | 16-bit | Name | Purpose |
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|----------|----------|---------|---------------------|---------------------------------------------------------|
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| `rsp` | `esp` | `sp` | Stack Pointer | Points to the top of the stack |
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| `rbp` | `ebp` | `bp` | Base Pointer | Marks the base of the current stack frame |
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| `rip` | `eip` | `ip` | Instruction Pointer | Points to the next instruction to execute |
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| `rflags` | `eflags` | `flags` | Flags Register | Stores CPU state flags (zero, carry, sign, overflow...) |
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#### General-purpose registers
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| 64-bit | 32-bit | 16-bit | 8-bit high | 8-bit low | Category | Conventional use |
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|--------|--------|--------|------------|-----------|----------|-----------------|
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| `rax` | `eax` | `ax` | `ah` | `al` | Caller-saved | Return value, accumulator |
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| `rbx` | `ebx` | `bx` | `bh` | `bl` | Callee-saved | General purpose |
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| `rcx` | `ecx` | `cx` | `ch` | `cl` | Caller-saved | 4th argument |
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| `rdx` | `edx` | `dx` | `dh` | `dl` | Caller-saved | 3rd argument |
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| `rsi` | `esi` | `si` | - | `sil` | Caller-saved | 2nd argument |
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| `rdi` | `edi` | `di` | - | `dil` | Caller-saved | 1st argument |
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| `r8` | `r8d` | `r8w` | - | `r8b` | Caller-saved | 5th argument |
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| `r9` | `r9d` | `r9w` | - | `r9b` | Caller-saved | 6th argument |
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| `r10`–`r11` | `r10d`–`r11d` | `r10w`–`r11w` | - | `r10b`–`r11b` | Caller-saved | Scratch |
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| `r12`–`r15` | `r12d`–`r15d` | `r12w`–`r15w` | - | `r12b`–`r15b` | Callee-saved | General purpose |
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| 64-bit | 32-bit | 16-bit | 8-bit high | 8-bit low | Category | Conventional use |
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|-------------|---------------|---------------|------------|---------------|--------------|---------------------------|
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| `rax` | `eax` | `ax` | `ah` | `al` | Caller-saved | Return value, accumulator |
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| `rbx` | `ebx` | `bx` | `bh` | `bl` | Callee-saved | General purpose |
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| `rcx` | `ecx` | `cx` | `ch` | `cl` | Caller-saved | 4th argument |
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| `rdx` | `edx` | `dx` | `dh` | `dl` | Caller-saved | 3rd argument |
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| `rsi` | `esi` | `si` | - | `sil` | Caller-saved | 2nd argument |
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| `rdi` | `edi` | `di` | - | `dil` | Caller-saved | 1st argument |
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| `r8` | `r8d` | `r8w` | - | `r8b` | Caller-saved | 5th argument |
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| `r9` | `r9d` | `r9w` | - | `r9b` | Caller-saved | 6th argument |
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| `r10`–`r11` | `r10d`–`r11d` | `r10w`–`r11w` | - | `r10b`–`r11b` | Caller-saved | Scratch |
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| `r12`–`r15` | `r12d`–`r15d` | `r12w`–`r15w` | - | `r12b`–`r15b` | Callee-saved | General purpose |
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> Writing to a 32-bit register (e.g. `eax`) zeroes the upper 32 bits of its 64-bit counterpart (`rax`).
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> Writing to a 16-bit or 8-bit register leaves the upper bits unchanged.
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@ -67,58 +67,58 @@ All computation happens inside registers - RAM just holds the data until it’s
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#### Base
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| Instruction | Description |
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|-------------|-------------|
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| `mov dst, src` | Copy src into dst |
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| `push src` | Push src onto the stack |
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| `pop dst` | Pop top of stack into dst |
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| Instruction | Description |
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|------------------|----------------------------------------|
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| `mov dst, src` | Copy src into dst |
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| `push src` | Push src onto the stack |
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| `pop dst` | Pop top of stack into dst |
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| `lea dst, [src]` | Load effective address of src into dst |
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#### Branching
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##### Flag-setting
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| Instruction | Flags set | Description |
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|-------------|-----------|-------------|
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| `cmp a, b` | ZF, SF, OF, CF | Computes `a − b`, discards result |
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| `test a, b` | ZF, SF, PF | Computes `a AND b`, discards result |
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| Instruction | Flags set | Description |
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|-------------|----------------|-------------------------------------|
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| `cmp a, b` | ZF, SF, OF, CF | Computes `a − b`, discards result |
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| `test a, b` | ZF, SF, PF | Computes `a AND b`, discards result |
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##### Conditional jumps
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| Instruction | Flags | Condition | Description |
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|-------------|-------|-----------|-------------|
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| `jmp` | - | always | Unconditional jump |
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| `je` / `jz` | ZF | ZF = 1 | Equal / Zero |
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| `jne` / `jnz` | ZF | ZF = 0 | Not equal / Not zero |
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| `jo` | OF | OF = 1 | Overflow |
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| `jno` | OF | OF = 0 | No overflow |
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| `js` | SF | SF = 1 | Sign (negative) |
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| `jns` | SF | SF = 0 | No sign (positive) |
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| `jg` | ZF, SF, OF | ZF=0 ∧ SF=OF | Greater (signed) |
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| `jge` | SF, OF | SF = OF | Greater or equal (signed) |
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| `jl` | SF, OF | SF ≠ OF | Less (signed) |
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| `jle` | ZF, SF, OF | ZF=1 ∨ SF≠OF | Less or equal (signed) |
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| `ja` | CF, ZF | CF=0 ∧ ZF=0 | Above (unsigned) |
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| `jae` | CF | CF = 0 | Above or equal (unsigned) |
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| `jb` | CF | CF = 1 | Below (unsigned) |
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| `jbe` | CF, ZF | CF=1 ∨ ZF=1 | Below or equal (unsigned) |
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| Instruction | Flags | Condition | Description |
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|---------------|------------|--------------|---------------------------|
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| `jmp` | - | always | Unconditional jump |
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| `je` / `jz` | ZF | ZF = 1 | Equal / Zero |
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| `jne` / `jnz` | ZF | ZF = 0 | Not equal / Not zero |
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| `jo` | OF | OF = 1 | Overflow |
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| `jno` | OF | OF = 0 | No overflow |
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| `js` | SF | SF = 1 | Sign (negative) |
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| `jns` | SF | SF = 0 | No sign (positive) |
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| `jg` | ZF, SF, OF | ZF=0 ∧ SF=OF | Greater (signed) |
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| `jge` | SF, OF | SF = OF | Greater or equal (signed) |
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| `jl` | SF, OF | SF ≠ OF | Less (signed) |
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| `jle` | ZF, SF, OF | ZF=1 ∨ SF≠OF | Less or equal (signed) |
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| `ja` | CF, ZF | CF=0 ∧ ZF=0 | Above (unsigned) |
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| `jae` | CF | CF = 0 | Above or equal (unsigned) |
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| `jb` | CF | CF = 1 | Below (unsigned) |
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| `jbe` | CF, ZF | CF=1 ∨ ZF=1 | Below or equal (unsigned) |
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#### Arithmetic
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| Instruction | Description |
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|-------------|-------------|
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| `add dst, src` | dst = dst + src |
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| `sub dst, src` | dst = dst - src |
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| `inc dst` | dst = dst + 1 |
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| `dec dst` | dst = dst - 1 |
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| `imul dst, src` | dst = dst * src (signed) |
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| `mul src` | rax * src → rdx:rax (unsigned) |
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| `idiv src` | rdx:rax / src → rax (quotient), rdx (remainder) (signed) |
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| `div src` | rdx:rax / src → rax (quotient), rdx (remainder) (unsigned) |
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| `neg dst` | dst = -dst |
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| `and dst, src` | dst = dst AND src |
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| `or dst, src` | dst = dst OR src |
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| `xor dst, src` | dst = dst XOR src (used to zero a register when dst == src) |
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| Instruction | Description |
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|-----------------|-------------------------------------------------------------|
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| `add dst, src` | dst = dst + src |
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| `sub dst, src` | dst = dst - src |
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| `inc dst` | dst = dst + 1 |
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| `dec dst` | dst = dst - 1 |
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| `imul dst, src` | dst = dst * src (signed) |
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| `mul src` | rax * src → rdx:rax (unsigned) |
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| `idiv src` | rdx:rax / src → rax (quotient), rdx (remainder) (signed) |
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| `div src` | rdx:rax / src → rax (quotient), rdx (remainder) (unsigned) |
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| `neg dst` | dst = -dst |
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| `and dst, src` | dst = dst AND src |
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| `or dst, src` | dst = dst OR src |
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| `xor dst, src` | dst = dst XOR src (used to zero a register when dst == src) |
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### System call
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@ -158,10 +158,10 @@ Additional arguments are pushed onto the stack. The return value is stored in `r
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**Register preservation:**
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| Type | Registers | Who saves | Behavior |
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|------|-----------|-----------|----------|
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| Caller-saved | `rax`, `rcx`, `rdx`, `rsi`, `rdi`, `r8`–`r11` | Caller | **Will be overwritten** by the called function - save them before `call` if needed |
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| Callee-saved | `rbx`, `rbp`, `r12`–`r15` | Callee | Must be restored before returning |
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| Type | Registers | Who saves | Behavior |
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|--------------|-----------------------------------------------|-----------|------------------------------------------------------------------------------------|
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| Caller-saved | `rax`, `rcx`, `rdx`, `rsi`, `rdi`, `r8`–`r11` | Caller | **Will be overwritten** by the called function - save them before `call` if needed |
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| Callee-saved | `rbx`, `rbp`, `r12`–`r15` | Callee | Must be restored before returning |
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#### Structure of a function
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