From: Anshuman Khandual <anshuman.khandual@arm.com>
To: James Morse <james.morse@arm.com>,
kexec@lists.infradead.org, linux-mm@kvack.org,
linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Bhupesh Sharma <bhsharma@redhat.com>,
Will Deacon <will@kernel.org>,
Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image
Date: Fri, 27 Mar 2020 06:13:06 +0530 [thread overview]
Message-ID: <c4764e40-96d5-e2e4-6479-dc8d167e25e0@arm.com> (raw)
In-Reply-To: <20200326180730.4754-2-james.morse@arm.com>
On 03/26/2020 11:37 PM, James Morse wrote:
> An image loaded for kexec is not stored in place, instead its segments
> are scattered through memory, and are re-assembled when needed. In the
> meantime, the target memory may have been removed.
>
> Because mm is not aware that this memory is still in use, it allows it
> to be removed.
Why the isolation process does not fail when these pages are currently
being used by kexec ?
>
> Add a memory notifier to prevent the removal of memory regions that
> overlap with a loaded kexec image segment. e.g., when triggered from the
> Qemu console:
> | kexec_core: memory region in use
> | memory memory32: Offline failed.
Yes this is definitely an added protection for these kexec loaded kernels
memory areas from being offlined but I would have expected the preceding
offlining to have failed as well.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> kernel/kexec_core.c | 56 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 56 insertions(+)
>
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index c19c0dad1ebe..ba1d91e868ca 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -12,6 +12,7 @@
> #include <linux/slab.h>
> #include <linux/fs.h>
> #include <linux/kexec.h>
> +#include <linux/memory.h>
> #include <linux/mutex.h>
> #include <linux/list.h>
> #include <linux/highmem.h>
> @@ -22,10 +23,12 @@
> #include <linux/elf.h>
> #include <linux/elfcore.h>
> #include <linux/utsname.h>
> +#include <linux/notifier.h>
> #include <linux/numa.h>
> #include <linux/suspend.h>
> #include <linux/device.h>
> #include <linux/freezer.h>
> +#include <linux/pfn.h>
> #include <linux/pm.h>
> #include <linux/cpu.h>
> #include <linux/uaccess.h>
> @@ -1219,3 +1222,56 @@ void __weak arch_kexec_protect_crashkres(void)
>
> void __weak arch_kexec_unprotect_crashkres(void)
> {}
> +
> +/*
> + * If user-space wants to offline memory that is in use by a loaded kexec
> + * image, it should unload the image first.
> + */
Probably this would need kexec user manual and related system call man pages
update as well.
> +static int mem_remove_cb(struct notifier_block *nb, unsigned long action,
> + void *data)
> +{
> + int rv = NOTIFY_OK, i;
> + struct memory_notify *arg = data;
> + unsigned long pfn = arg->start_pfn;
> + unsigned long nr_segments, sstart, send;
> + unsigned long end_pfn = arg->start_pfn + arg->nr_pages;
> +
> + might_sleep();
Required ?
> +
> + if (action != MEM_GOING_OFFLINE)
> + return NOTIFY_DONE;
> +
> + mutex_lock(&kexec_mutex);
> + if (kexec_image) {
> + nr_segments = kexec_image->nr_segments;
> +
> + for (i = 0; i < nr_segments; i++) {
> + sstart = PFN_DOWN(kexec_image->segment[i].mem);
> + send = PFN_UP(kexec_image->segment[i].mem +
> + kexec_image->segment[i].memsz);
> +
> + if ((pfn <= sstart && sstart < end_pfn) ||
> + (pfn <= send && send < end_pfn)) {
> + pr_warn("Memory region in use\n");
> + rv = NOTIFY_BAD;
> + break;
> + }
> + }
> + }
> + mutex_unlock(&kexec_mutex);
> +
> + return rv;
Variable 'rv' is redundant, should use NOTIFY_[BAD|OK] directly instead.
> +}
> +
> +static struct notifier_block mem_remove_nb = {
> + .notifier_call = mem_remove_cb,
> +};
> +
> +static int __init register_mem_remove_cb(void)
> +{
> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
Should not all these new code here be wrapped with CONFIG_MEMORY_HOTREMOVE
to reduce the scope as well as final code size when the config is disabled.
> + return register_memory_notifier(&mem_remove_nb);
> +
> + return 0;
> +}
> +device_initcall(register_mem_remove_cb);
>
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next prev parent reply other threads:[~2020-03-27 0:43 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 18:07 [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use James Morse
2020-03-26 18:07 ` [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image James Morse
2020-03-27 0:43 ` Anshuman Khandual [this message]
2020-03-27 2:54 ` Baoquan He
2020-03-27 15:46 ` James Morse
2020-03-27 2:34 ` Baoquan He
2020-03-27 9:30 ` David Hildenbrand
2020-03-27 16:56 ` James Morse
2020-03-27 17:06 ` David Hildenbrand
2020-03-27 18:07 ` James Morse
2020-03-27 18:52 ` David Hildenbrand
2020-03-30 13:00 ` James Morse
2020-03-30 13:13 ` David Hildenbrand
2020-03-30 17:17 ` James Morse
2020-03-30 18:14 ` David Hildenbrand
2020-04-10 19:10 ` Andrew Morton
2020-04-11 3:44 ` Baoquan He
2020-04-11 9:30 ` Russell King - ARM Linux admin
2020-04-11 9:58 ` David Hildenbrand
2020-04-12 5:35 ` Baoquan He
2020-04-12 8:08 ` Russell King - ARM Linux admin
2020-04-12 19:52 ` Eric W. Biederman
2020-04-12 20:37 ` Bhupesh SHARMA
2020-04-13 2:37 ` Baoquan He
2020-04-13 13:15 ` Eric W. Biederman
2020-04-13 23:01 ` Andrew Morton
2020-04-14 6:13 ` Eric W. Biederman
2020-04-14 6:40 ` Baoquan He
2020-04-14 6:51 ` Baoquan He
2020-04-14 8:00 ` David Hildenbrand
2020-04-14 9:22 ` Baoquan He
2020-04-14 9:37 ` David Hildenbrand
2020-04-14 14:39 ` Baoquan He
2020-04-14 14:49 ` David Hildenbrand
2020-04-15 2:35 ` Baoquan He
2020-04-16 13:31 ` David Hildenbrand
2020-04-16 14:02 ` Baoquan He
2020-04-16 14:09 ` David Hildenbrand
2020-04-16 14:36 ` Baoquan He
2020-04-16 14:47 ` David Hildenbrand
2020-04-21 13:29 ` David Hildenbrand
2020-04-21 13:57 ` David Hildenbrand
2020-04-21 13:59 ` Eric W. Biederman
2020-04-21 14:30 ` David Hildenbrand
2020-04-22 9:17 ` Baoquan He
2020-04-22 9:24 ` David Hildenbrand
2020-04-22 9:57 ` Baoquan He
2020-04-22 10:05 ` David Hildenbrand
2020-04-22 10:36 ` Baoquan He
2020-04-14 9:16 ` Dave Young
2020-04-14 9:38 ` Dave Young
2020-04-14 7:05 ` David Hildenbrand
2020-04-14 16:55 ` James Morse
2020-04-14 17:41 ` David Hildenbrand
2020-04-15 20:33 ` Eric W. Biederman
2020-04-22 12:28 ` James Morse
2020-04-22 15:25 ` Eric W. Biederman
2020-04-22 16:40 ` David Hildenbrand
2020-04-23 16:29 ` Eric W. Biederman
2020-04-24 7:39 ` David Hildenbrand
2020-04-24 7:41 ` David Hildenbrand
2020-05-01 16:55 ` James Morse
2020-03-26 18:07 ` [PATCH 2/3] mm/memory_hotplug: Allow arch override of non boot memory resource names James Morse
2020-03-27 9:59 ` David Hildenbrand
2020-03-27 15:39 ` James Morse
2020-03-30 13:23 ` David Hildenbrand
2020-03-30 17:17 ` James Morse
2020-04-02 5:49 ` Dave Young
2020-04-02 6:12 ` piliu
2020-04-14 17:21 ` James Morse
2020-04-15 20:36 ` Eric W. Biederman
2020-04-22 12:14 ` James Morse
2020-05-09 0:45 ` Andrew Morton
2020-05-11 8:35 ` David Hildenbrand
2020-03-26 18:07 ` [PATCH 3/3] arm64: memory: Give hotplug memory a different resource name James Morse
2020-03-30 19:01 ` David Hildenbrand
2020-04-15 20:37 ` Eric W. Biederman
2020-04-22 12:14 ` James Morse
2020-03-27 2:11 ` [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use Baoquan He
2020-03-27 15:40 ` James Morse
2020-03-27 9:27 ` David Hildenbrand
2020-03-27 15:42 ` James Morse
2020-03-30 13:18 ` David Hildenbrand
2020-03-30 13:55 ` Baoquan He
2020-03-30 17:17 ` James Morse
2020-03-31 3:46 ` Dave Young
2020-04-14 17:31 ` James Morse
2020-03-31 3:38 ` Dave Young
2020-04-15 20:29 ` Eric W. Biederman
2020-04-22 12:14 ` James Morse
2020-04-22 13:04 ` Eric W. Biederman
2020-04-22 15:40 ` James Morse
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