Re: [RFC]confusion about syscall

[王哲 <wangzhe5004@xxxxxxxxx>]

2012/7/15 Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx>

Hi...

On Sun, Jul 15, 2012 at 9:28 AM, 王哲 <wangzhe5004@xxxxxxxxx> wrote:
> and the second program:
>
> #include <stdio.h>
> #include <unistd.h>
>
> int main(void)
> {
>     unsigned long value = 0;
>     value = getpid();
>     return 0;
> }
>
> and disassembling it:( objdump -d a.out)
> ...
> 08048300 <getpid@plt>:
>  8048300:    ff 25 00 a0 04 08        jmp    *0x804a000
>  8048306:    68 00 00 00 00           push   $0x0
>  804830b:    e9 e0 ff ff ff           jmp    80482f0 <_init+0x3c>

Looks like jumping into vsyscall page to me...

   thanks for reply.
   and i wander why the address of vsyscall page is not 0xffffe000 in my system?
...
b7806000-b7807000 r-xp 00000000 00:00 0          [vdso]
b7807000-b7827000 r-xp 00000000 08:08 2491275    /lib/i386-linux-gnu/ld-2.15.so
b7827000-b7828000 r--p 0001f000 08:08 2491275    /lib/i386-linux-gnu/ld-2.15.so
b7828000-b7829000 rw-p 00020000 08:08 2491275    /lib/i386-linux-gnu/ld-2.15.so
 ...

root@glinuxi-G31M-ES2C:~# ldd /bin/ls
    linux-gate.so.1 =>  (0xb786b000)
    libselinux.so.1 => /lib/i386-linux-gnu/libselinux.so.1 (0xb7839000)
    librt.so.1 => /lib/i386-linux-gnu/librt.so.1 (0xb7830000)
    libacl.so.1 => /lib/i386-linux-gnu/libacl.so.1 (0xb7826000)
...

--
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

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

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