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Date: Thu, 21 Feb 2019 14:46:36 -0800
From: Kees Cook <keescook@...omium.org>
To: Aaro Koskinen <aaro.koskinen@....fi>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Aaro Koskinen <aaro.koskinen@...ia.com>
Subject: Re: [RESEND PATCH v2] panic/reboot: allow specifying reboot_mode for
panic only
On Thu, Feb 21, 2019 at 12:33 PM Aaro Koskinen <aaro.koskinen@....fi> wrote:
>
> From: Aaro Koskinen <aaro.koskinen@...ia.com>
>
> Allow specifying reboot_mode for panic only. This is needed on systems
> where ramoops is used to store panic logs, and user wants to use warm
> reset to preserve those, while still having cold reset on normal reboots.
>
> Signed-off-by: Aaro Koskinen <aaro.koskinen@...ia.com>
> ---
>
> v2: Use REBOOT_UNDEFINED instead of -1
>
> v1: https://marc.info/?t=154957416600005&r=1&w=2
>
> .../admin-guide/kernel-parameters.txt | 4 +++-
> include/linux/reboot.h | 2 ++
> kernel/panic.c | 2 ++
> kernel/reboot.c | 20 ++++++++++++++-----
> 4 files changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 858b6c0b9a15..5705b4689565 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3949,7 +3949,9 @@
> [[,]s[mp]#### \
> [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
> [[,]f[orce]
> - Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
> + Where reboot_mode is one of warm (soft) or cold (hard) or gpio
> + (prefix with 'panic_' to set mode for panic
> + reboot only),
> reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
> reboot_force is either force or not specified,
> reboot_cpu is s[mp]#### with #### being the processor
> diff --git a/include/linux/reboot.h b/include/linux/reboot.h
> index e63799a6e895..1c4c8a47e2de 100644
> --- a/include/linux/reboot.h
> +++ b/include/linux/reboot.h
> @@ -19,8 +19,10 @@ enum reboot_mode {
> REBOOT_HARD,
> REBOOT_SOFT,
> REBOOT_GPIO,
> + REBOOT_UNDEFINED = -1,
I would expect this before REBOOT_COLD (numerically ordered).
> };
> extern enum reboot_mode reboot_mode;
> +extern enum reboot_mode panic_reboot_mode;
>
> enum reboot_type {
> BOOT_TRIPLE = 't',
> diff --git a/kernel/panic.c b/kernel/panic.c
> index f121e6ba7e11..a0d839f883b7 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -306,6 +306,8 @@ void panic(const char *fmt, ...)
> * shutting down. But if there is a chance of
> * rebooting the system it will be rebooted.
> */
> + if (panic_reboot_mode != REBOOT_UNDEFINED)
> + reboot_mode = panic_reboot_mode;
> emergency_restart();
> }
> #ifdef __sparc__
> diff --git a/kernel/reboot.c b/kernel/reboot.c
> index e1b79b6a2735..b9e79e8c7226 100644
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -31,6 +31,7 @@ EXPORT_SYMBOL(cad_pid);
> #define DEFAULT_REBOOT_MODE
> #endif
> enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
> +enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
>
> /*
> * This variable is used privately to keep track of whether or not
> @@ -519,6 +520,8 @@ EXPORT_SYMBOL_GPL(orderly_reboot);
> static int __init reboot_setup(char *str)
> {
> for (;;) {
> + enum reboot_mode *mode;
> +
> /*
> * Having anything passed on the command line via
> * reboot= will cause us to disable DMI checking
> @@ -526,17 +529,24 @@ static int __init reboot_setup(char *str)
> */
> reboot_default = 0;
>
> + if (!strncmp(str, "panic_", 6)) {
> + mode = &panic_reboot_mode;
> + str += 6;
> + } else {
> + mode = &reboot_mode;
> + }
> +
> switch (*str) {
> case 'w':
> - reboot_mode = REBOOT_WARM;
> + *mode = REBOOT_WARM;
> break;
>
> case 'c':
> - reboot_mode = REBOOT_COLD;
> + *mode = REBOOT_COLD;
> break;
>
> case 'h':
> - reboot_mode = REBOOT_HARD;
> + *mode = REBOOT_HARD;
> break;
>
> case 's':
> @@ -553,11 +563,11 @@ static int __init reboot_setup(char *str)
> if (rc)
> return rc;
> } else
> - reboot_mode = REBOOT_SOFT;
> + *mode = REBOOT_SOFT;
> break;
> }
> case 'g':
> - reboot_mode = REBOOT_GPIO;
> + *mode = REBOOT_GPIO;
> break;
>
> case 'b':
> --
> 2.17.0
>
Everything else looks good, though!
--
Kees Cook
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