22 Dec, 2011
1 commit
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Mathieu Desnoyers pointed out a case that can cause issues with
NMIs running on the debug stack:int3 -> interrupt -> NMI -> int3
Because the interrupt changes the stack, the NMI will not see that
it preempted the debug stack. Looking deeper at this case,
interrupts only happen when the int3 is from userspace or in
an a location in the exception table (fixup).userspace -> int3 -> interurpt -> NMI -> int3
All other int3s that happen in the kernel should be processed
without ever enabling interrupts, as the do_trap() call will
panic the kernel if it is called to process any other location
within the kernel.Adding a counter around the sections that enable interrupts while
using the debug stack allows the NMI to also check that case.
If the NMI sees that it either interrupted a task using the debug
stack or the debug counter is non-zero, then it will have to
change the IDT table to make the int3 not change stacks (which will
corrupt the stack if it does).Note, I had to move the debug_usage functions out of processor.h
and into debugreg.h because of the static inlined functions to
inc and dec the debug_usage counter. __get_cpu_var() requires
smp.h which includes processor.h, and would fail to build.Link: http://lkml.kernel.org/r/1323976535.23971.112.camel@gandalf.stny.rr.com
Reported-by: Mathieu Desnoyers
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: H. Peter Anvin
Cc: Thomas Gleixner
Cc: Paul Turner
Cc: Frederic Weisbecker
Signed-off-by: Steven Rostedt
30 Dec, 2010
1 commit
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Go through x86 code and replace __get_cpu_var and get_cpu_var
instances that refer to a scalar and are not used for address
determinations.Cc: Yinghai Lu
Cc: Ingo Molnar
Acked-by: Tejun Heo
Acked-by: "H. Peter Anvin"
Signed-off-by: Christoph Lameter
Signed-off-by: Tejun Heo
29 Jan, 2010
1 commit
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Clear the reserved bits from the stored copy of debug status
register (DR6).
This will help easy bitwise operations such as quick testing
of a debug event origin.Signed-off-by: K.Prasad
Cc: Roland McGrath
Cc: Jan Kiszka
Cc: Alan Stern
Cc: Ingo Molnar
LKML-Reference:
Signed-off-by: Frederic Weisbecker
25 Nov, 2009
1 commit
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Percpu symbols now occupy the same namespace as other global
symbols and as such short global symbols without subsystem
prefix tend to collide with local variables. dr7 percpu
variable used by x86 was hit by this. Rename it to cpu_dr7.The rename also makes it more consistent with its fellow
cpu_debugreg percpu variable.Signed-off-by: Tejun Heo
Cc: Frederic Weisbecker
Cc: Peter Zijlstra
Cc: Rusty Russell
Cc: Christoph Lameter
Cc: Linus Torvalds ,
Cc: Andrew Morton
LKML-Reference:
Signed-off-by: Ingo Molnar
Reported-by: Stephen Rothwell
14 Nov, 2009
1 commit
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This build error:
arch/x86/kvm/x86.c:3655: error: implicit declaration of function 'hw_breakpoint_restore'
Happens because in the CONFIG_KVM=m case there's no 'CONFIG_KVM' define
in the kernel - it's CONFIG_KVM_MODULE in that case.Make the prototype available unconditionally.
Cc: Frederic Weisbecker
Cc: Prasad
LKML-Reference:
Signed-off-by: Ingo Molnar
10 Nov, 2009
2 commits
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Wrap in the cpu dr7 check that tells if we have active
breakpoints that need to be restored in the cpu.This wrapper makes the check more self-explainable and also
reusable for any further other uses.Reported-by: Jan Kiszka
Signed-off-by: Frederic Weisbecker
Cc: Avi Kivity
Cc: "K. Prasad" -
Fix the broken a.out format dump. For now we only dump the ptrace
breakpoints.TODO: Dump every perf breakpoints for the current thread, not only
ptrace based ones.Reported-by: Ingo Molnar
Signed-off-by: Frederic Weisbecker
Cc: "K. Prasad"
08 Nov, 2009
1 commit
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This patch rebase the implementation of the breakpoints API on top of
perf events instances.Each breakpoints are now perf events that handle the
register scheduling, thread/cpu attachment, etc..The new layering is now made as follows:
ptrace kgdb ftrace perf syscall
\ | / /
\ | / /
/
Core breakpoint API /
/
| /
| /Breakpoints perf events
|
|Breakpoints PMU ---- Debug Register constraints handling
(Part of core breakpoint API)
|
|Hardware debug registers
Reasons of this rewrite:
- Use the centralized/optimized pmu registers scheduling,
implying an easier arch integration
- More powerful register handling: perf attributes (pinned/flexible
events, exclusive/non-exclusive, tunable period, etc...)Impact:
- New perf ABI: the hardware breakpoints counters
- Ptrace breakpoints setting remains tricky and still needs some per
thread breakpoints references.Todo (in the order):
- Support breakpoints perf counter events for perf tools (ie: implement
perf_bpcounter_event())
- Support from perf toolsChanges in v2:
- Follow the perf "event " rename
- The ptrace regression have been fixed (ptrace breakpoint perf events
weren't released when a task ended)
- Drop the struct hw_breakpoint and store generic fields in
perf_event_attr.
- Separate core and arch specific headers, drop
asm-generic/hw_breakpoint.h and create linux/hw_breakpoint.h
- Use new generic len/type for breakpoint
- Handle off case: when breakpoints api is not supported by an archChanges in v3:
- Fix broken CONFIG_KVM, we need to propagate the breakpoint api
changes to kvm when we exit the guest and restore the bp registers
to the host.Changes in v4:
- Drop the hw_breakpoint_restore() stub as it is only used by KVM
- EXPORT_SYMBOL_GPL hw_breakpoint_restore() as KVM can be built as a
module
- Restore the breakpoints unconditionally on kvm guest exit:
TIF_DEBUG_THREAD doesn't anymore cover every cases of running
breakpoints and vcpu->arch.switch_db_regs might not always be
set when the guest used debug registers.
(Waiting for a reliable optimization)Changes in v5:
- Split-up the asm-generic/hw-breakpoint.h moving to
linux/hw_breakpoint.h into a separate patch
- Optimize the breakpoints restoring while switching from kvm guest
to host. We only want to restore the state if we have active
breakpoints to the host, otherwise we don't care about messed-up
address registers.
- Add asm/hw_breakpoint.h to Kbuild
- Fix bad breakpoint type in trace_selftest.cChanges in v6:
- Fix wrong header inclusion in trace.h (triggered a build
error with CONFIG_FTRACE_SELFTESTSigned-off-by: Frederic Weisbecker
Cc: Prasad
Cc: Alan Stern
Cc: Peter Zijlstra
Cc: Arnaldo Carvalho de Melo
Cc: Steven Rostedt
Cc: Ingo Molnar
Cc: Jan Kiszka
Cc: Jiri Slaby
Cc: Li Zefan
Cc: Avi Kivity
Cc: Paul Mackerras
Cc: Mike Galbraith
Cc: Masami Hiramatsu
Cc: Paul Mundt
03 Jun, 2009
1 commit
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The generic hardware breakpoint interface provides an abstraction of
hardware breakpoints in front of specific arch implementations for both kernel
and user side breakpoints.
This includes execution breakpoints and read/write breakpoints, also known as
"watchpoints".This patch introduces header files containing constants, structure definitions
and declaration of functions used by the hardware breakpoint core and x86
specific code.
It also introduces an array based storage for the debug-register values in
'struct thread_struct', while modifying all users of debugreg member in the
structure.[ Impact: add headers for new hardware breakpoint interface ]
Original-patch-by: Alan Stern
Signed-off-by: K.Prasad
Reviewed-by: Alan Stern
Signed-off-by: Frederic Weisbecker
23 Oct, 2008
2 commits
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Change header guards named "ASM_X86__*" to "_ASM_X86_*" since:
a. the double underscore is ugly and pointless.
b. no leading underscore violates namespace constraints.Signed-off-by: H. Peter Anvin
-
Signed-off-by: Al Viro
Signed-off-by: H. Peter Anvin
