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    SubjectRe: [PATCH] x86: Setup early console as early as possible
    On Mon, Jul 12, 2010 at 08:47:03AM -0700, H. Peter Anvin wrote:
    > On 07/12/2010 01:58 AM, Pekka Enberg wrote:
    > > Hi Yinghai,
    > >
    > > Yinghai Lu wrote:
    > >> Analyze "console=uart8250,io,0x3f8,115200n8" in
    > >> i386_start_kernel/x86_64_start_kernel,
    > >> and call setup_early_serial8250_console() to init early serial console.
    > >>
    > >> only can handle io port kind of 8250. because mmio need ioremap.
    > >>
    > >> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    > >
    > > What's the purpose of this patch? Does it make my early boot I/O patch
    > > obsolete?
    > >
    > > Pekka
    >
    > No, they're complementary. Your patch serial-port enables the RM
    > kernel, whereas Yinghai pushes the initialization earlier in the PM kernel.
    >
    > Incidentally, Yinghai: it would be possible to push even an MMIO
    > reference earlier by reserving a fixmap slot for the early console. I'm
    > not sure if it's worth it, though.
    >
    > -hpa
    >

    Peter, while reviewing this patch I found another nit in
    context of early_param usage, so the patch is below. It's
    completely trivial. Actually I thought I've already fixed
    all early_param cases long ago but this one somehow sneaked ;)

    Anyway, Yinghai, Peter,

    I'm not sure but can't we use some boot_param "pad" field for
    "being copied" flag instead of new variable? There is a case
    when boot_param is used as __initdata and I'm not sure we clear
    this section explicitly.

    -- Cyrill
    ---
    From: Cyrill Gorcunov <gorcunov@openvz.org>
    Subject: [PATCH] early console: Prevent early_param null dereference

    In case if user passes "earlycon" without args there will
    be null dereference.

    Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
    ---
    drivers/serial/8250_early.c | 3 +++
    1 file changed, 3 insertions(+)

    Index: linux-2.6.git/drivers/serial/8250_early.c
    =====================================================================
    --- linux-2.6.git.orig/drivers/serial/8250_early.c
    +++ linux-2.6.git/drivers/serial/8250_early.c
    @@ -217,6 +217,9 @@ int __init setup_early_serial8250_consol
    char *options;
    int err;

    + if (!cmdline)
    + return 0;
    +
    options = strstr(cmdline, "uart8250,");
    if (!options) {
    options = strstr(cmdline, "uart,");

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