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From: Mulyadi Santosa <mulyadi.santosa@gmail.com>
Date: Thu, 4 Feb 2010 02:25:43 +0700
Message-ID: <f284c33d1002031125j72e8f6e0m5f381166b194c127@mail.gmail.com>
Subject: Re: [Qemu-devel] [Please discard the previous mail] System call from
	a Guest Linux
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To: Jong Chun Park <joumon@gmail.com>
Cc: qemu-devel@nongnu.org

Hi Jong

(Sorry, I am not sure how to politely call a Korean name...so
apologize if it turns out to be rude...)

On Thu, Feb 4, 2010 at 1:08 AM, Jong Chun Park <joumon@gmail.com> wrote:
> after compilation in the guest OS:
> int main() {
> =A0=A0 int fd;
> =A0=A0 if (access("hello.txt", R_OK) !=3D 0) {
> =A0=A0 =A0 exit(0);
> =A0=A0 }
> =A0=A0 fd=3Dopen("hello.txt", O_RDONLY);
> =A0=A0 close(fd);
> =A0=A0 return 0;
> }
>
> For this simple sequence of system calls, acess() -> open() -> close(), Q=
EMU
> goes through disas_insn() and helper_sysenter() more than 3 times. This
> makes me really confused because I believed those should be called 3 time=
s,
> though. It'd be greatly appreciated in advance if someone helps me out th=
is.
> Thanks a lot,
> Jong

Try to run that compile and run that code under strace (without using
Qemu, I mean), then you'll understand how many system calls are
executed.

clues: opening certain libraries, doing mmap() s and so on

--=20
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com