linux-kernel - [Patch 0/1] HW-BKPT: Allow per-cpu kernel-space Hardware Breakpoint requests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090817124641.GA13354@in.ibm.com>
Date:	Mon, 17 Aug 2009 18:16:41 +0530
From:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Alan Stern <stern@...land.harvard.edu>
Subject: [Patch 0/1] HW-BKPT: Allow per-cpu kernel-space Hardware
	Breakpoint requests

Hi All,
	Please find a patch that enables kernel-space breakpoints to be
requested for a subset of the available CPUs in the system. This allows
per-CPU breakpoints and comes with the associated benefit of reduced
overhead during (un)registration.

This enhancement allows exploitation of hardware breakpoint registers by
'perf' which produces a CPU-wise information.

Design changes
--------------
- Every breakpoint request 'consumes' the first available debug register
  (starting from HBP_NUM) in each CPU represented by 'cpumask' field in
  'struct hw_breakpoint'.

- 'hbp_kernel_pos' (that separates kernel-space breakpoints from the
  free/user-space breakpoints) now points to the maximum of debug
  registers consumed on any given CPU.
  -- 'hbp_kernel_pos' is decremented (one-at-a-time) to allow a new-slot
     for kernel-space requests iff all debug registers on the given CPU
     (from HBP_NUM - 1 to 'hbp_kernel_pos' are already consumed.
  -- 'hbp_kernel_pos' is incremented (one-at-a-time) to free a slot iff
     a removal request results in the release of a bkpt request that
     consumed maximum debug registers for kernel-space.

- Every removal request results in compaction of breakpoint registers
  (on a per-cpu basis) to occupy the vacant debug register.
 
The patch is based on commit b6c720b811aed0eeda89f277f13c1bd1bdf721fd of
-tip tree and has been tested to work fine on an x86 machine for both
cases (i.e. system-wide kernel breakpoints and bkpts for a subset of CPUs).

Please let me know your comments on the same.

Thanks,
K.Prasad

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/