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Date: Fri, 26 Dec 2014 21:35:06 +0300
From: Andrei Borzenkov <arvidjaar@gmail.com>
To: Alexander Kuleshov <kuleshovmail@gmail.com>
Subject: Re: esp register value after jump to linux
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=D0=92 Thu, 25 Dec 2014 00:59:36 +0600
Alexander Kuleshov <kuleshovmail@gmail.com> =D0=BF=D0=B8=D1=88=D0=B5=D1=82:

> Hello all,
>=20
> I see that grub setups registers before jump to linux kernel at
> grub/grub-core/loader/i386/pc/linux.c:
>=20
> grub_linux16_boot (void)
>=20
> {
>=20
>   ...
>=20
>   state.gs =3D state.fs =3D state.es =3D state.Tds =3D state.ss =3D segme=
nt;
>=20
>   state.sp =3D GRUB_LINUX_SETUP_STACK;
>=20
>   state.cs =3D segment + 0x20;
>=20
>   state.ip =3D 0;
>=20
>   ...
>=20
> }
>=20
> I see in gdb that: ss, ds, and other segment registers are 0x1000, and
> cs is 0x1020. It is good. But why esp is 0xf7f4? I see that
> GRUB_LINUX_SETUP_STACK is 0x9000.
>=20

It is absolutely unclear at which point, where and how you get content
of ESP.