linux-toradex.git/kernel/kexec_core.c, branch v4.8-rc1

kexec: add restriction on kexec_load() segment sizes

2016-08-02T23:35:31+00:00

I hit the following issue when run trinity in my system.  The kernel is
3.4 version, but mainline has the same issue.

The root cause is that the segment size is too large so the kerenl
spends too long trying to allocate a page.  Other cases will block until
the test case quits.  Also, OOM conditions will occur.

Call Trace:
  __alloc_pages_nodemask+0x14c/0x8f0
  alloc_pages_current+0xaf/0x120
  kimage_alloc_pages+0x10/0x60
  kimage_alloc_control_pages+0x5d/0x270
  machine_kexec_prepare+0xe5/0x6c0
  ? kimage_free_page_list+0x52/0x70
  sys_kexec_load+0x141/0x600
  ? vfs_write+0x100/0x180
  system_call_fastpath+0x16/0x1b

The patch changes sanity_check_segment_list() to verify that the usage by
all segments does not exceed half of memory.

[akpm@linux-foundation.org: fix for kexec-return-error-number-directly.patch, update comment]
Link: http://lkml.kernel.org/r/1469625474-53904-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang 
Suggested-by: Eric W. Biederman 
Cc: Vivek Goyal 
Cc: Dave Young 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec: add a kexec_crash_loaded() function

2016-08-02T23:35:30+00:00

Provide a wrapper function to be used by kernel code to check whether a
crash kernel is loaded.  It returns the same value that can be seen in
/sys/kernel/kexec_crash_loaded by userspace programs.

I'm exporting the function, because it will be used by Xen, and it is
possible to compile Xen modules separately to enable the use of PV
drivers with unmodified bare-metal kernels.

Link: http://lkml.kernel.org/r/20160713121955.14969.69080.stgit@hananiah.suse.cz
Signed-off-by: Petr Tesarik 
Cc: Juergen Gross 
Cc: Josh Triplett 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Cc: Eric Biederman 
Cc: "H. Peter Anvin" 
Cc: Boris Ostrovsky 
Cc: "Paul E. McKenney" 
Cc: Dave Young 
Cc: David Vrabel 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec: allow architectures to override boot mapping

2016-08-02T23:35:27+00:00

kexec physical addresses are the boot-time view of the system.  For
certain ARM systems (such as Keystone 2), the boot view of the system
does not match the kernel's view of the system: the boot view uses a
special alias in the lower 4GB of the physical address space.

To cater for these kinds of setups, we need to translate between the
boot view physical addresses and the normal kernel view physical
addresses.  This patch extracts the current transation points into
linux/kexec.h, and allows an architecture to override the functions.

Due to the translations required, we unfortunately end up with six
translation functions, which are reduced down to four that the
architecture can override.

[akpm@linux-foundation.org: kexec.h needs asm/io.h for phys_to_virt()]
Link: http://lkml.kernel.org/r/E1b8koP-0004HZ-Vf@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King 
Cc: Keerthy 
Cc: Pratyush Anand 
Cc: Vitaly Andrianov 
Cc: Eric Biederman 
Cc: Dave Young 
Cc: Baoquan He 
Cc: Vivek Goyal 
Cc: Simon Horman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kdump: arrange for paddr_vmcoreinfo_note() to return phys_addr_t

2016-08-02T23:35:27+00:00

On PAE systems (eg, ARM LPAE) the vmcore note may be located above 4GB
physical on 32-bit architectures, so we need a wider type than "unsigned
long" here.  Arrange for paddr_vmcoreinfo_note() to return a
phys_addr_t, thereby allowing it to be located above 4GB.

This makes no difference for kexec-tools, as they already assume a
64-bit type when reading from this file.

Link: http://lkml.kernel.org/r/E1b8koK-0004HS-K9@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King 
Reviewed-by: Pratyush Anand 
Acked-by: Baoquan He 
Cc: Keerthy 
Cc: Vitaly Andrianov 
Cc: Eric Biederman 
Cc: Dave Young 
Cc: Vivek Goyal 
Cc: Simon Horman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec: ensure user memory sizes do not wrap

2016-08-02T23:35:26+00:00

Ensure that user memory sizes do not wrap around when validating the
user input, which can lead to the following input validation working
incorrectly.

[akpm@linux-foundation.org: fix it for kexec-return-error-number-directly.patch]
Link: http://lkml.kernel.org/r/E1b8koF-0004HM-5x@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King 
Reviewed-by: Pratyush Anand 
Acked-by: Baoquan He 
Cc: Keerthy 
Cc: Vitaly Andrianov 
Cc: Eric Biederman 
Cc: Dave Young 
Cc: Vivek Goyal 
Cc: Simon Horman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec: return error number directly

2016-08-02T23:35:24+00:00

This is a cleanup patch to make kexec more clear to return error number
directly.  The variable result is useless, because there is no other
function's return value assignes to it.  So remove it.

Link: http://lkml.kernel.org/r/1464179273-57668-1-git-send-email-mnghuan@gmail.com
Signed-off-by: Minfei Huang 
Cc: Dave Young 
Cc: Baoquan He 
Cc: Borislav Petkov 
Cc: Xunlei Pang 
Cc: Atsushi Kumagai 
Cc: Vivek Goyal 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

s390/kexec: consolidate crash_map/unmap_reserved_pages() and arch_kexec_protect(unprotect)_crashkres()

2016-05-24T00:04:14+00:00

Commit 3f625002581b ("kexec: introduce a protection mechanism for the
crashkernel reserved memory") is a similar mechanism for protecting the
crash kernel reserved memory to previous crash_map/unmap_reserved_pages()
implementation, the new one is more generic in name and cleaner in code
(besides, some arch may not be allowed to unmap the pgtable).

Therefore, this patch consolidates them, and uses the new
arch_kexec_protect(unprotect)_crashkres() to replace former
crash_map/unmap_reserved_pages() which by now has been only used by
S390.

The consolidation work needs the crash memory to be mapped initially,
this is done in machine_kdump_pm_init() which is after
reserve_crashkernel().  Once kdump kernel is loaded, the new
arch_kexec_protect_crashkres() implemented for S390 will actually
unmap the pgtable like before.

Signed-off-by: Xunlei Pang 
Signed-off-by: Michael Holzheu 
Acked-by: Michael Holzheu 
Cc: Heiko Carstens 
Cc: "Eric W. Biederman" 
Cc: Minfei Huang 
Cc: Vivek Goyal 
Cc: Dave Young 
Cc: Baoquan He 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec: introduce a protection mechanism for the crashkernel reserved memory

2016-05-24T00:04:14+00:00

For the cases that some kernel (module) path stamps the crash reserved
memory(already mapped by the kernel) where has been loaded the second
kernel data, the kdump kernel will probably fail to boot when panic
happens (or even not happens) leaving the culprit at large, this is
unacceptable.

The patch introduces a mechanism for detecting such cases:

1) After each crash kexec loading, it simply marks the reserved memory
   regions readonly since we no longer access it after that.  When someone
   stamps the region, the first kernel will panic and trigger the kdump.
   The weak arch_kexec_protect_crashkres() is introduced to do the actual
   protection.

2) To allow multiple loading, once 1) was done we also need to remark
   the reserved memory to readwrite each time a system call related to
   kdump is made.  The weak arch_kexec_unprotect_crashkres() is introduced
   to do the actual protection.

The architecture can make its specific implementation by overriding
arch_kexec_protect_crashkres() and arch_kexec_unprotect_crashkres().

Signed-off-by: Xunlei Pang 
Cc: Eric Biederman 
Cc: Dave Young 
Cc: Minfei Huang 
Cc: Vivek Goyal 
Cc: Baoquan He 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

printk/nmi: flush NMI messages on the system panic

2016-05-21T00:58:30+00:00

In NMI context, printk() messages are stored into per-CPU buffers to
avoid a possible deadlock.  They are normally flushed to the main ring
buffer via an IRQ work.  But the work is never called when the system
calls panic() in the very same NMI handler.

This patch tries to flush NMI buffers before the crash dump is
generated.  In this case it does not risk a double release and bails out
when the logbuf_lock is already taken.  The aim is to get the messages
into the main ring buffer when possible.  It makes them better
accessible in the vmcore.

Then the patch tries to flush the buffers second time when other CPUs
are down.  It might be more aggressive and reset logbuf_lock.  The aim
is to get the messages available for the consequent kmsg_dump() and
console_flush_on_panic() calls.

The patch causes vprintk_emit() to be called even in NMI context again.
But it is done via printk_deferred() so that the console handling is
skipped.  Consoles use internal locks and we could not prevent a
deadlock easily.  They are explicitly called later when the crash dump
is not generated, see console_flush_on_panic().

Signed-off-by: Petr Mladek 
Cc: Benjamin Herrenschmidt 
Cc: Daniel Thompson 
Cc: David Miller 
Cc: Ingo Molnar 
Cc: Jan Kara 
Cc: Jiri Kosina 
Cc: Martin Schwidefsky 
Cc: Peter Zijlstra 
Cc: Ralf Baechle 
Cc: Russell King 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: rename _count, field of the struct page, to _refcount

2016-05-20T02:12:14+00:00

Many developers already know that field for reference count of the
struct page is _count and atomic type.  They would try to handle it
directly and this could break the purpose of page reference count
tracepoint.  To prevent direct _count modification, this patch rename it
to _refcount and add warning message on the code.  After that, developer
who need to handle reference count will find that field should not be
accessed directly.

[akpm@linux-foundation.org: fix comments, per Vlastimil]
[akpm@linux-foundation.org: Documentation/vm/transhuge.txt too]
[sfr@canb.auug.org.au: sync ethernet driver changes]
Signed-off-by: Joonsoo Kim 
Signed-off-by: Stephen Rothwell 
Cc: Vlastimil Babka 
Cc: Hugh Dickins 
Cc: Johannes Berg 
Cc: "David S. Miller" 
Cc: Sunil Goutham 
Cc: Chris Metcalf 
Cc: Manish Chopra 
Cc: Yuval Mintz 
Cc: Tariq Toukan 
Cc: Saeed Mahameed 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds