Do not allocate the buffer for the code on the stack

Gabriel Corona · Gabriel Corona · commit fd900c59d54c · 2015-07-15T17:27:37.000+02:00
Use the heap instead.
diff --git a/src/Disassembler.cpp b/src/Disassembler.cpp
@@ -98,10 +98,12 @@ void Disassembler::disassemble(std::ostream& stream, std::uint64_t start, std::u
 
 void Disassembler::disassemble(std::ostream& stream, Symbol const& symbol)
 {
-  uint8_t buffer[symbol.size];
+  if (this->buffer_.size() < symbol.size)
+    this->buffer_.resize(symbol.size);
+
   struct iovec local, remote;
 
-  local.iov_base = buffer;
+  local.iov_base = this->buffer_.data();
   local.iov_len = symbol.size;
 
   remote.iov_base = (void*) symbol.value;
@@ -114,7 +116,7 @@ void Disassembler::disassemble(std::ostream& stream, Symbol const& symbol)
   }
 
   stream << std::hex << symbol.value << '<' << symbol.name << ">\n";
-  this->disassemble(stream, buffer, symbol.size, symbol.value);
+  this->disassemble(stream, this->buffer_.data(), symbol.size, symbol.value);
   stream << '\n';
 }
 
diff --git a/src/unjit.hpp b/src/unjit.hpp
@@ -160,6 +160,7 @@ class Disassembler {
 private:
   Process* process_;
   LLVMDisasmContextRef disassembler_;
+  std::vector<std::uint8_t> buffer_;
 public:
   Disassembler(Process& process);
   ~Disassembler();

Original file line number	Diff line number	Diff line change
`@@ -98,10 +98,12 @@ void Disassembler::disassemble(std::ostream& stream, std::uint64_t start, std::u`
`98`	`98`
`99`	`99`	`void Disassembler::disassemble(std::ostream& stream, Symbol const& symbol)`
`100`	`100`	`{`
`101`		`- uint8_t buffer[symbol.size];`
	`101`	`+ if (this->buffer_.size() < symbol.size)`
	`102`	`+ this->buffer_.resize(symbol.size);`
	`103`	`+`
`102`	`104`	`struct iovec local, remote;`
`103`	`105`
`104`		`- local.iov_base = buffer;`
	`106`	`+ local.iov_base = this->buffer_.data();`
`105`	`107`	`local.iov_len = symbol.size;`
`106`	`108`
`107`	`109`	`remote.iov_base = (void*) symbol.value;`
`@@ -114,7 +116,7 @@ void Disassembler::disassemble(std::ostream& stream, Symbol const& symbol)`
`114`	`116`	`}`
`115`	`117`
`116`	`118`	`stream << std::hex << symbol.value << '<' << symbol.name << ">\n";`
`117`		`- this->disassemble(stream, buffer, symbol.size, symbol.value);`
	`119`	`+ this->disassemble(stream, this->buffer_.data(), symbol.size, symbol.value);`
`118`	`120`	`stream << '\n';`
`119`	`121`	`}`
`120`	`122`