Date: Wed, 03 Sep 2014 17:03:44 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: "Sinha, Prokash" <psinha@panasas.com> Subject: Re: PXE boot Message-ID: <1641492.zXWdUoX4Sh@ralph.baldwin.cx> In-Reply-To: <D02C8BE1.179F%psinha@panasas.com> References: <D02C8BE1.179F%psinha@panasas.com>
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On Wednesday, September 03, 2014 04:12:01 PM Sinha, Prokash wrote:
> Hi All,
>=20
> I'm trying to understand the invocation of the routines pxe_init();
> pxe_open() etc. in pxe.c
>=20
> By the structure, it looks like a driver with devsw_pxedisk =3D { ent=
ry points
> =E2=80=A6}
>=20
> Once this pxeldr is brought down from the net boot server, how does i=
t get
> invoked ( or rather who calls these routines ) ??? The loader ( strap=
ped
> with it don't seem to call).
>=20
> I assume that the the boot code in the NVRAM ( or wherever ) of the N=
IC that
> supports calls these pxe_* () functions ???
pxeboot is pxeldr + /boot/loader. The firmware (BIOS or EFI) downloads=
the=20
pxeboot binary to a known fixed address and starts executing it. When =
it=20
starts executing, pxeldr finds the /boot/loader binary "behind" it and=20=
arranges for it to run. It passes a flag telling it that it was booted=
via=20
PXE. The loader then uses the routines in pxe.c to talk to firmware on=
the=20
NIC. The firmware provides both TFTP and UDP interfaces. The loader u=
ses=20
those to provide either a TFTP "filesystem" or to mount an NFS filesyst=
em over=20
UDP.
--=20
John Baldwin
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