DSPDisassembler: Fix out-of-bounds read when the last word is an instruction with a large immediate

For instance, ending with 0x009e (which you can do with CW 0x009e) indicates a LRI $ac0.m instruction, but there is no immediate value to load, so before whatever garbage in memory existed after the end of the file was used.

The bounds-checking also previously assumed that IRAM or IROM was being used, both of which were exactly 0x1000 long.
This commit is contained in:
Pokechu22 2022-06-13 18:34:17 -07:00
parent dc353ed84d
commit cad9801ded
4 changed files with 34 additions and 13 deletions

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@ -78,9 +78,9 @@ bool Compare(const std::vector<u16>& code1, const std::vector<u16>& code2)
{ {
std::string line1, line2; std::string line1, line2;
u16 pc = i; u16 pc = i;
disassembler.DisassembleOpcode(&code1[0], &pc, line1); disassembler.DisassembleOpcode(code1, &pc, line1);
pc = i; pc = i;
disassembler.DisassembleOpcode(&code2[0], &pc, line2); disassembler.DisassembleOpcode(code2, &pc, line2);
fmt::print("!! {:04x} : {:04x} vs {:04x} - {} vs {}\n", i, code1[i], code2[i], line1, fmt::print("!! {:04x} : {:04x} vs {:04x} - {} vs {}\n", i, code1[i], code2[i], line1,
line2); line2);
} }
@ -93,7 +93,7 @@ bool Compare(const std::vector<u16>& code1, const std::vector<u16>& code2)
{ {
u16 pc = i; u16 pc = i;
std::string line; std::string line;
disassembler.DisassembleOpcode(&longest[0], &pc, line); disassembler.DisassembleOpcode(longest, &pc, line);
fmt::print("!! {}\n", line); fmt::print("!! {}\n", line);
} }
} }

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@ -33,9 +33,10 @@ bool DSPDisassembler::Disassemble(const std::vector<u16>& code, std::string& tex
for (u16 pc = 0; pc < code.size();) for (u16 pc = 0; pc < code.size();)
{ {
if (!DisassembleOpcode(code.data(), &pc, text)) bool failed = !DisassembleOpcode(code, &pc, text);
return false;
text.append("\n"); text.append("\n");
if (failed)
return false;
} }
return true; return true;
} }
@ -139,16 +140,23 @@ std::string DSPDisassembler::DisassembleParameters(const DSPOPCTemplate& opc, u1
return buf; return buf;
} }
bool DSPDisassembler::DisassembleOpcode(const u16* binbuf, u16* pc, std::string& dest) bool DSPDisassembler::DisassembleOpcode(const std::vector<u16>& code, u16* pc, std::string& dest)
{ {
if ((*pc & 0x7fff) >= 0x1000) return DisassembleOpcode(code.data(), code.size(), pc, dest);
}
bool DSPDisassembler::DisassembleOpcode(const u16* binbuf, size_t binbuf_size, u16* pc,
std::string& dest)
{
const u16 wrapped_pc = (*pc & 0x7fff);
if (wrapped_pc >= binbuf_size)
{ {
++pc; ++pc;
dest.append("; outside memory"); dest.append("; outside memory");
return false; return false;
} }
const u16 op1 = binbuf[*pc & 0x0fff]; const u16 op1 = binbuf[wrapped_pc];
// Find main opcode // Find main opcode
const DSPOPCTemplate* opc = FindOpInfoByOpcode(op1); const DSPOPCTemplate* opc = FindOpInfoByOpcode(op1);
@ -179,14 +187,23 @@ bool DSPDisassembler::DisassembleOpcode(const u16* binbuf, u16* pc, std::string&
// printing // printing
if (settings_.show_pc) if (settings_.show_pc)
dest += fmt::format("{:04x} ", *pc); dest += fmt::format("{:04x} ", wrapped_pc);
u16 op2; u16 op2;
// Size 2 - the op has a large immediate. // Size 2 - the op has a large immediate.
if (opc->size == 2) if (opc->size == 2)
{ {
op2 = binbuf[(*pc + 1) & 0x0fff]; if (wrapped_pc + 1 >= binbuf_size)
{
if (settings_.show_hex)
dest += fmt::format("{:04x} ???? ", op1);
dest += fmt::format("; Insufficient data for large immediate");
*pc += opc->size;
return false;
}
op2 = binbuf[wrapped_pc + 1];
if (settings_.show_hex) if (settings_.show_hex)
dest += fmt::format("{:04x} {:04x} ", op1, op2); dest += fmt::format("{:04x} {:04x} ", op1, op2);
} }

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@ -34,8 +34,10 @@ public:
bool Disassemble(const std::vector<u16>& code, std::string& text); bool Disassemble(const std::vector<u16>& code, std::string& text);
// Warning - this one is trickier to use right. // Disassembles the given opcode at pc and increases pc by the opcode's size.
bool DisassembleOpcode(const u16* binbuf, u16* pc, std::string& dest); // The PC is wrapped such that 0x0000 and 0x8000 both point to the start of the buffer.
bool DisassembleOpcode(const std::vector<u16>& code, u16* pc, std::string& dest);
bool DisassembleOpcode(const u16* binbuf, size_t binbuf_size, u16* pc, std::string& dest);
private: private:
std::string DisassembleParameters(const DSPOPCTemplate& opc, u16 op1, u16 op2); std::string DisassembleParameters(const DSPOPCTemplate& opc, u16 op1, u16 op2);

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@ -77,13 +77,15 @@ void AutoDisassembly(const SDSP& dsp, u16 start_addr, u16 end_addr)
u16 addr = start_addr; u16 addr = start_addr;
const u16* ptr = (start_addr >> 15) != 0 ? dsp.irom : dsp.iram; const u16* ptr = (start_addr >> 15) != 0 ? dsp.irom : dsp.iram;
constexpr size_t size = DSP_IROM_SIZE;
static_assert(size == DSP_IRAM_SIZE);
while (addr < end_addr) while (addr < end_addr)
{ {
line_to_addr[line_counter] = addr; line_to_addr[line_counter] = addr;
addr_to_line[addr] = line_counter; addr_to_line[addr] = line_counter;
std::string buf; std::string buf;
if (!disasm.DisassembleOpcode(ptr, &addr, buf)) if (!disasm.DisassembleOpcode(ptr, size, &addr, buf))
{ {
ERROR_LOG_FMT(DSPLLE, "disasm failed at {:04x}", addr); ERROR_LOG_FMT(DSPLLE, "disasm failed at {:04x}", addr);
break; break;