Re: [Dotgnu-libjit] How Do I Debug a Memory Protection Error?

[Noah Lavine]

Hello,

> What does the address look like on which the bus error is raised?
> The OS X abi for x86_64 should be SysV abi or do you know about any
> differences?

The address is 0x00000001007bb480.

> Does gdb print the contents of the address?
> like with print *(char *)(address)
>
> Enter the command "display /8i $pc" in gdb before running the faulting
> program and run it to get the assembly instructions where the error
> actually happens.

It looks like the assembly is

0x1007bb480:    add    %bl,0x10070(%rsi)
0x1007bb486:    add    %al,(%rax)
0x1007bb488:    add    %al,(%rax)
0x1007bb48a:    add    %al,(%rax)
0x1007bb48c:    add    %al,(%rax)
0x1007bb48e:    add    %al,(%rax)
0x1007bb490:    xorb   $0x0,0x1007b(%rax)
0x1007bb497:    add    %al,(%rax)

So unless I misunderstand things, this looks like memory that never
had code put in it, which means the error is that a pointer was
changed somewhere. Is this accurate?

Thanks,
Noah