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POHow to get the assembly code from IonMonkey
 

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  1. POHow to get the assembly code from IonMonkey
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    <p>for studying purposes I am trying to find out the memory address of a variable after JIT compilation from IonMonkey ( IonMonkey is part of SpiderMonkey, the Javascript engine of Mozilla )</p> <p>Until now I have followed these instruction <a href="https://developer.mozilla.org/en-US/docs/SpiderMonkey/Hacking_Tips#Printing_the_generated_assembly_code_(from_gdb)" rel="nofollow">https://developer.mozilla.org/en-US/docs/SpiderMonkey/Hacking_Tips#Printing_the_generated_assembly_code_(from_gdb)</a></p> <p>I use GDB and I run the same procedure with 2 different test files.</p> <pre><code> function f(a, b) { return a + b; } var shell = "AAAA"; for (var i = 0; i &lt; 1000000; i++){ f( shell[0], shell[1] ); } </code></pre> <p>and this one:</p> <pre><code>function f(a, b) { return a + b; } var shell = "AAAA"; for (var i = 0; i &lt; 1000000; i++){ f( shell[1], shell[1] ); } </code></pre> <p>I believed that this way I would spot the difference between the generated code and find out where is the "shell" variable is located. The problem is that the generated code is exactly the same. I also tried different versions of simple function such as minus or print but the generated code is totally different.</p> <p>Can anyone suggest any way so I can get the memory address of the variable?</p> <p>The assembly generated code is </p> <pre><code> 0x7ffff7ff3ac8: mov 0x20(%rsp),%r10 0x7ffff7ff3acd: shr $0x2f,%r10 0x7ffff7ff3ad1: cmp $0x1fff2,%r10d 0x7ffff7ff3ad8: je 0x7ffff7ff3ae3 0x7ffff7ff3ade: jmpq 0x7ffff7ff3b85 0x7ffff7ff3ae3: mov 0x28(%rsp),%r10 0x7ffff7ff3ae8: shr $0x2f,%r10 0x7ffff7ff3aec: cmp $0x1fff5,%r10d 0x7ffff7ff3af3: je 0x7ffff7ff3afe 0x7ffff7ff3af9: jmpq 0x7ffff7ff3b85 0x7ffff7ff3afe: mov 0x30(%rsp),%r10 0x7ffff7ff3b03: shr $0x2f,%r10 0x7ffff7ff3b07: cmp $0x1fff5,%r10d 0x7ffff7ff3b0e: je 0x7ffff7ff3b19 0x7ffff7ff3b14: jmpq 0x7ffff7ff3b85 0x7ffff7ff3b19: mov 0x28(%rsp),%r8 0x7ffff7ff3b1e: movabs $0x7fffffffffff,%rax 0x7ffff7ff3b28: and %r8,%rax 0x7ffff7ff3b2b: mov 0x30(%rsp),%r9 0x7ffff7ff3b30: movabs $0x7fffffffffff,%rdi 0x7ffff7ff3b3a: and %r9,%rdi 0x7ffff7ff3b3d: mov $0x1670b78,%r11d 0x7ffff7ff3b43: mov (%r11),%rcx 0x7ffff7ff3b46: cmp %rcx,%rsp 0x7ffff7ff3b49: jbe 0x7ffff7ff3b8f 0x7ffff7ff3b4f: callq 0x7ffff7ff39a0 0x7ffff7ff3b54: test %rbp,%rbp 0x7ffff7ff3b57: je 0x7ffff7ff3bd6 0x7ffff7ff3b5d: movabs $0xfffa800000000000,%rcx 0x7ffff7ff3b67: or %rbp,%rcx 0x7ffff7ff3b6a: retq 0x7ffff7ff3b6b: nop ... 0x7ffff7ff3b72: nop 0x7ffff7ff3b73: movabs $0xffffffffffffffff,%r11 0x7ffff7ff3b7d: push %r11 0x7ffff7ff3b7f: callq 0x7ffff7fe9400 0x7ffff7ff3b84: int3 0x7ffff7ff3b85: pushq $0x0 0x7ffff7ff3b8a: jmpq 0x7ffff7ff3c40 0x7ffff7ff3b8f: sub $0x28,%rsp 0x7ffff7ff3b93: mov %r9,0x20(%rsp) 0x7ffff7ff3b98: mov %r8,0x18(%rsp) 0x7ffff7ff3b9d: mov %rdi,0x10(%rsp) 0x7ffff7ff3ba2: mov %rcx,0x8(%rsp) 0x7ffff7ff3ba7: mov %rax,(%rsp) 0x7ffff7ff3bab: pushq $0x280 0x7ffff7ff3bb0: callq 0x7ffff7fee880 0x7ffff7ff3bb5: mov 0x20(%rsp),%r9 0x7ffff7ff3bba: mov 0x18(%rsp),%r8 0x7ffff7ff3bbf: mov 0x10(%rsp),%rdi 0x7ffff7ff3bc4: mov 0x8(%rsp),%rcx 0x7ffff7ff3bc9: mov (%rsp),%rax 0x7ffff7ff3bcd: add $0x28,%rsp 0x7ffff7ff3bd1: jmpq 0x7ffff7ff3b4f 0x7ffff7ff3bd6: sub $0x40,%rsp 0x7ffff7ff3bda: mov %r9,0x38(%rsp) 0x7ffff7ff3bdf: mov %r8,0x30(%rsp) 0x7ffff7ff3be4: mov %rdi,0x28(%rsp) 0x7ffff7ff3be9: mov %rsi,0x20(%rsp) 0x7ffff7ff3bee: mov %rbx,0x18(%rsp) 0x7ffff7ff3bf3: mov %rdx,0x10(%rsp) 0x7ffff7ff3bf8: mov %rcx,0x8(%rsp) 0x7ffff7ff3bfd: mov %rax,(%rsp) 0x7ffff7ff3c01: push %rdi 0x7ffff7ff3c02: push %rax 0x7ffff7ff3c03: pushq $0x500 0x7ffff7ff3c08: callq 0x7ffff7fec370 0x7ffff7ff3c0d: mov %rax,%rbp 0x7ffff7ff3c10: mov 0x38(%rsp),%r9 0x7ffff7ff3c15: mov 0x30(%rsp),%r8 0x7ffff7ff3c1a: mov 0x28(%rsp),%rdi 0x7ffff7ff3c1f: mov 0x20(%rsp),%rsi 0x7ffff7ff3c24: mov 0x18(%rsp),%rbx 0x7ffff7ff3c29: mov 0x10(%rsp),%rdx 0x7ffff7ff3c2e: mov 0x8(%rsp),%rcx 0x7ffff7ff3c33: mov (%rsp),%rax 0x7ffff7ff3c37: add $0x40,%rsp 0x7ffff7ff3c3b: jmpq 0x7ffff7ff3b5d 0x7ffff7ff3c40: pushq $0x0 0x7ffff7ff3c45: jmpq 0x7ffff7fe9008 0x7ffff7ff3c4a: hlt </code></pre>
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