From c6c405336bd3b0ebd1d76aaf9ea88b35dba77e61 Mon Sep 17 00:00:00 2001 From: Kairui Song Date: Tue, 16 Jul 2019 16:26:39 -0700 Subject: [PATCH] vmcore: add a kernel parameter novmcoredd Since commit 2724273e8fd0 ("vmcore: add API to collect hardware dump in second kernel"), drivers are allowed to add device related dump data to vmcore as they want by using the device dump API. This has a potential issue, the data is stored in memory, drivers may append too much data and use too much memory. The vmcore is typically used in a kdump kernel which runs in a pre-reserved small chunk of memory. So as a result it will make kdump unusable at all due to OOM issues. So introduce new 'novmcoredd' command line option. User can disable device dump to reduce memory usage. This is helpful if device dump is using too much memory, disabling device dump could make sure a regular vmcore without device dump data is still available. [akpm@linux-foundation.org: tweak documentation] [akpm@linux-foundation.org: vmcore.c needs moduleparam.h] Link: http://lkml.kernel.org/r/20190528111856.7276-1-kasong@redhat.com Signed-off-by: Kairui Song Acked-by: Dave Young Reviewed-by: Bhupesh Sharma Cc: Rahul Lakkireddy Cc: "David S . Miller" Cc: Eric Biederman Cc: Alexey Dobriyan Cc: Baoquan He Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++++ fs/proc/Kconfig | 3 ++- fs/proc/vmcore.c | 9 +++++++++ 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index f8b62360b18c..bf8221abfe0a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2877,6 +2877,17 @@ /sys/module/printk/parameters/console_suspend) to turn on/off it dynamically. + novmcoredd [KNL,KDUMP] + Disable device dump. Device dump allows drivers to + append dump data to vmcore so you can collect driver + specified debug info. Drivers can append the data + without any limit and this data is stored in memory, + so this may cause significant memory stress. Disabling + device dump can help save memory but the driver debug + data will be no longer available. This parameter + is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP + is set. + noaliencache [MM, NUMA, SLAB] Disables the allocation of alien caches in the slab allocator. Saves per-node memory, but will impact performance. diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig index 4c3dcb718961..cba429db95d9 100644 --- a/fs/proc/Kconfig +++ b/fs/proc/Kconfig @@ -58,7 +58,8 @@ config PROC_VMCORE_DEVICE_DUMP snapshot. If you say Y here, the collected device dumps will be added - as ELF notes to /proc/vmcore. + as ELF notes to /proc/vmcore. You can still disable device + dump using the kernel command line option 'novmcoredd'. config PROC_SYSCTL bool "Sysctl support (/proc/sys)" if EXPERT diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c index 57957c91c6df..7bcc92add72c 100644 --- a/fs/proc/vmcore.c +++ b/fs/proc/vmcore.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -54,6 +55,9 @@ static struct proc_dir_entry *proc_vmcore; /* Device Dump list and mutex to synchronize access to list */ static LIST_HEAD(vmcoredd_list); static DEFINE_MUTEX(vmcoredd_mutex); + +static bool vmcoredd_disabled; +core_param(novmcoredd, vmcoredd_disabled, bool, 0); #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */ /* Device Dump Size */ @@ -1452,6 +1456,11 @@ int vmcore_add_device_dump(struct vmcoredd_data *data) size_t data_size; int ret; + if (vmcoredd_disabled) { + pr_err_once("Device dump is disabled\n"); + return -EINVAL; + } + if (!data || !strlen(data->dump_name) || !data->vmcoredd_callback || !data->size) return -EINVAL; -- 2.30.2