On Mon, Oct 26, 2020 at 07:54:27PM -0400, Sasha Levin wrote:
From: Douglas Anderson dianders@chromium.org
[ Upstream commit b18b099e04f450cdc77bec72acefcde7042bd1f3 ]
On my system the kernel processes the "kgdb_earlycon" parameter before the "kgdbcon" parameter. When we setup "kgdb_earlycon" we'll end up in kgdb_register_callbacks() and "kgdb_use_con" won't have been set yet so we'll never get around to starting "kgdbcon". Let's remedy this by detecting that the IO module was already registered when setting "kgdb_use_con" and registering the console then.
As part of this, to avoid pre-declaring things, move the handling of the "kgdbcon" further down in the file.
Signed-off-by: Douglas Anderson dianders@chromium.org Link: https://lore.kernel.org/r/20200630151422.1.I4aa062751ff5e281f5116655c976dff5... Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org
kgdb[oc]_earlycon was a new feature introduced in v5.8 so, based on the summary above, this fix does not obviously apply to older kernels.
However after looking closely...
I think the issue described above would also occur if kgdbdbgp (an incomprehensible sequence consonants that translates to "present debugger via USB EHCI debug") were used in conjunction with kgdbcon meaning backporting does make sense.
Daniel.
kernel/debug/debug_core.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-)
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 2222f3225e53d..097ab02989f92 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -96,14 +96,6 @@ int dbg_switch_cpu; /* Use kdb or gdbserver mode */ int dbg_kdb_mode = 1; -static int __init opt_kgdb_con(char *str) -{
- kgdb_use_con = 1;
- return 0;
-}
-early_param("kgdbcon", opt_kgdb_con);
module_param(kgdb_use_con, int, 0644); module_param(kgdbreboot, int, 0644); @@ -876,6 +868,20 @@ static struct console kgdbcons = { .index = -1, }; +static int __init opt_kgdb_con(char *str) +{
- kgdb_use_con = 1;
- if (kgdb_io_module_registered && !kgdb_con_registered) {
register_console(&kgdbcons);kgdb_con_registered = 1;- }
- return 0;
+}
+early_param("kgdbcon", opt_kgdb_con);
#ifdef CONFIG_MAGIC_SYSRQ static void sysrq_handle_dbg(int key) { -- 2.25.1