linux-kernel - [RHEL6.8 Patch 1/3] kernel: audit/fix non-modular users of module

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Message-Id: <1437036437-25408-2-git-send-email-bhe@redhat.com>
Date:	Thu, 16 Jul 2015 16:46:56 +0800
From:	Baoquan He <bhe@...hat.com>
To:	linux-kernel@...r.kernel.org, ncroxon@...hat.com,
	dyoung@...hat.com, mhuang@...hat.com
Cc:	Baoquan He <bhe@...hat.com>
Subject: [RHEL6.8 Patch 1/3] kernel: audit/fix non-modular users of module_init in core code

Resolves: bz1236437
https://bugzilla.redhat.com/show_bug.cgi?id=1236437

Brew build:
https://brewweb.devel.redhat.com/taskinfo?taskID=9499237

This is back ported from upstream partionly.

The crash_notes data resides in the percpu in the first kernel.
While percpu use vmalloc to allocate by default. So if many percpu
data is needed it will cause crash_notes data crosses the page boundary.
When the second kernel tries to access this data using the physical
memory address, it sees incorrect data after crossing the page boundary.

In this patch kexec initialization from the 'device' phase to
'the 'subsys' phase. This can prevent crash_notes being allocated in
2 vmalloc pages.

commit c96d6660dc65b0a90aea9834bfd8be1d5656da18
Author: Paul Gortmaker <paul.gortmaker@...driver.com>
Date:   Thu Apr 3 14:48:35 2014 -0700

    kernel: audit/fix non-modular users of module_init in core code

    Code that is obj-y (always built-in) or dependent on a bool Kconfig
    (built-in or absent) can never be modular.  So using module_init as an
    alias for __initcall can be somewhat misleading.

    Fix these up now, so that we can relocate module_init from init.h into
    module.h in the future.  If we don't do this, we'd have to add module.h
    to obviously non-modular code, and that would be a worse thing.

    The audit targets the following module_init users for change:
     kernel/user.c                  obj-y
     kernel/kexec.c                 bool KEXEC (one instance per arch)
     kernel/profile.c               bool PROFILING
     kernel/hung_task.c             bool DETECT_HUNG_TASK
     kernel/sched/stats.c           bool SCHEDSTATS
     kernel/user_namespace.c        bool USER_NS

    Note that direct use of __initcall is discouraged, vs.  one of the
    priority categorized subgroups.  As __initcall gets mapped onto
    device_initcall, our use of subsys_initcall (which makes sense for these
    files) will thus change this registration from level 6-device to level
    4-subsys (i.e.  slightly earlier).  However no observable impact of that
    difference has been observed during testing.

    Also, two instances of missing ";" at EOL are fixed in kexec.

    Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
    Cc: Ingo Molnar <mingo@...hat.com>
    Cc: Peter Zijlstra <peterz@...radead.org>
    Cc: Eric Biederman <ebiederm@...ssion.com>
    Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 kernel/kexec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index d977250..779f803 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1246,7 +1246,7 @@ static int __init crash_notes_memory_init(void)
 	}
 	return 0;
 }
-module_init(crash_notes_memory_init)
+subsys_initcall(crash_notes_memory_init);
 
 
 /*
-- 
2.1.0

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