|| ||Avery Pennarun <email@example.com> |
|| ||Andrew Morton <firstname.lastname@example.org>,
Josh Triplett <email@example.com>,
"Paul E. McKenney" <firstname.lastname@example.org>,
Ingo Molnar <email@example.com>,
"David S. Miller" <firstname.lastname@example.org>,
Peter Zijlstra <email@example.com>,
"Fabio M. Di Nitto" <firstname.lastname@example.org>,
Avery Pennarun <email@example.com>,
Johannes Weiner <firstname.lastname@example.org>,
Olaf Hering <email@example.com>,
Paul Gortmaker <firstname.lastname@example.org>,
Tejun Heo <email@example.com>,
"H. Peter Anvin" <firstname.lastname@example.org>,
Yinghai LU <email@example.com>, firstname.lastname@example.org,
|| ||[PATCH 0/5] Persist printk buffer across reboots. |
|| ||Tue, 13 Mar 2012 01:36:36 -0400|
|| ||Article, Thread
The last patch in this series implements a new CONFIG_PRINTK_PERSIST option
that, when enabled, puts the printk buffer in a well-defined memory location
so that we can keep appending to it after a reboot. The upshot is that,
even after a kernel panic or non-panic hard lockup, on the next boot
userspace will be able to grab the kernel messages leading up to it. It
could then upload the messages to a server (for example) to keep crash
The preceding patches in the series are mostly just things I fixed up while
working on that patch.
- I'm not totally sure of the locking or portability issues when calling
memblock or bootmem. This all happens really early, and I *think*
interrupts are still disabled at that time, so it's probably okay.
- Tested this version on x86 (kvm) and it works with soft reboot (ie. reboot
-f). Since some BIOSes wipe the memory during boot, you might not have
any luck. It should be great on many embedded systems, though, including
the MIPS system I've tested a variant of this patch on. (Our MIPS build
is based on a slightly older kernel so it's not 100% the same, but I think
this should behave identically.)
- The way we choose a well-defined memory location is slightly suspicious
(we just count down from the top of the address space) but I've tested it
pretty carefully, and it seems to be okay.
- In printk.c with CONFIG_PRINTK_PERSIST set, we're #defining words like
log_end. It might be cleaner to replace all instances of log_end with
LOG_END to make this more clear. This is also the reason the struct
logbits members start with _: because otherwise they conflict with the
macro. Suggestions welcome.
Patch generated against v3.3-rc7.
Avery Pennarun (5):
mm: bootmem: BUG() if you try to allocate bootmem too late.
mm: bootmem: it's okay to reserve_bootmem an invalid address.
mm: nobootmem: implement reserve_bootmem() in terms of memblock.
printk: use alloc_bootmem() instead of memblock_alloc().
printk: CONFIG_PRINTK_PERSIST: persist printk buffer across reboots.
init/Kconfig | 12 ++++++
kernel/printk.c | 117 +++++++++++++++++++++++++++++++++++++++++++++---------
mm/bootmem.c | 10 ++++-
mm/nobootmem.c | 23 +++++++++++
4 files changed, 140 insertions(+), 22 deletions(-)
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