Messages in this thread | | | Date | Thu, 1 Aug 2002 12:37:47 -0700 (PDT) | From | Datoda <> | Subject | PTRACE_SYSCALL |
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Hi,
I have played with this ptrace request a bit on ia32 and there are a few things unclear to me. Could someone please answer my questions? TIA.
o When the child enters a system call, and the parent regains control after issuing PTRACE_SYSCALL, where is the system call number stored? I guess it's either in %eax or in orig_eax (at 0x24(esp)) of the child, but values in both places seem invalid in my own experiments.
o According to the man page, the child is interrupted twice for each system call, once at the entry and once at the exit. Intriguingly, when parent inspects the eip of the child at both interruptions, the two eip's are the same. What is the explanation for this? Furthermore, the eip of the child seems to always point at the instruction after "int". Why is that the case?
o Is there a good document that covers PTRACE_SYSCALL or ptrace in general?
Your answers are appreciated.
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