On 01/18/2010 09:45 AM, Peter Zijlstra wrote:
This is debugging. We're playing with registers, we're playing with the
cpu, we're playing with memory contents. Why not the address space as well?
Because you want thins go to be as transparent as possible in order to
avoid heisenbugs.
On Mon, 2010-01-18 at 13:01 +0200, Avi Kivity wrote:
You've made it clear that you don't like it, but not why.
The kernel already manages the user's address space (except for
MAP_FIXED which is unreliable unless you've already reserved the address
space). I don't see why adding a vma
On Mon, 2010-01-18 at 13:01 +0200, Avi Kivity wrote:
If we reserve some address space, you don't add any heisenbugs (at
least, not any additional ones over emulation). Even if we don't,
address space layout randomization means we're not keeping the address
space layout constant between
On 01/18/2010 01:44 PM, Peter Zijlstra wrote:
On Mon, 2010-01-18 at 13:01 +0200, Avi Kivity wrote:
You've made it clear that you don't like it, but not why.
The kernel already manages the user's address space (except for
MAP_FIXED which is unreliable unless you've already reserved the
On Mon, 2010-01-18 at 14:01 +0200, Avi Kivity wrote:
Maybe you place no value on uprobes. But people who debug userspace
likely will see a reason.
I do see value in uprobes, I just don't like it mucking about with the
address space. Nor does it appear required.
On 01/18/2010 02:06 PM, Peter Zijlstra wrote:
On Mon, 2010-01-18 at 14:01 +0200, Avi Kivity wrote:
Maybe you place no value on uprobes. But people who debug userspace
likely will see a reason.
I do see value in uprobes, I just don't like it mucking about with the
address space. Nor
Hi Avi,
On Mon, 2010-01-18 at 14:01 +0200, Avi Kivity wrote:
Maybe you place no value on uprobes. But people who debug userspace
likely will see a reason.
On 01/18/2010 02:06 PM, Peter Zijlstra wrote:
I do see value in uprobes, I just don't like it mucking about with the
address space. Nor
On 01/18/2010 02:13 PM, Pekka Enberg wrote:
So how big chunks of the address space are we talking here for uprobes?
That's for the authors to answer, but at a guess, 32 bytes per probe
(largest x86 instruction is 15 bytes), so 32 MB will give you a million
probes. That's a piece of cake
On Mon, 2010-01-18 at 14:17 +0200, Avi Kivity wrote:
On 01/18/2010 02:13 PM, Pekka Enberg wrote:
So how big chunks of the address space are we talking here for uprobes?
That's for the authors to answer, but at a guess, 32 bytes per probe
(largest x86 instruction is 15 bytes), so 32
* Avi Kivity a...@redhat.com [2010-01-18 14:17:10]:
On 01/18/2010 02:13 PM, Pekka Enberg wrote:
So how big chunks of the address space are we talking here for uprobes?
That's for the authors to answer, but at a guess, 32 bytes per probe
(largest x86 instruction is 15 bytes), so 32 MB will
On Mon, Jan 18, 2010 at 2:44 PM, Srikar Dronamraju
sri...@linux.vnet.ibm.com wrote:
* Avi Kivity a...@redhat.com [2010-01-18 14:17:10]:
On 01/18/2010 02:13 PM, Pekka Enberg wrote:
So how big chunks of the address space are we talking here for uprobes?
That's for the authors to answer, but at
On 01/18/2010 02:51 PM, Pekka Enberg wrote:
And how many probes do we expected to be live at the same time in
real-world scenarios? I guess Avi's one million is more than enough?
I don't think a user will ever come close to a million, but we can
expect some inflation from inlined
On 01/18/2010 02:51 PM, Pekka Enberg wrote:
And how many probes do we expected to be live at the same time in
real-world scenarios? I guess Avi's one million is more than enough?
Avi Kivity kirjoitti:
I don't think a user will ever come close to a million, but we can
expect some inflation
On Thu, Jan 14, 2010 at 01:29:09PM +0100, Peter Zijlstra wrote:
On Thu, 2010-01-14 at 13:23 +0100, Frederic Weisbecker wrote:
I see, so what you suggest is to have the probe set up
as generic first. Then the process that activates it
becomes a consumer, right?
Right, so either we have
On 01/18/2010 02:57 PM, Pekka Enberg wrote:
On 01/18/2010 02:51 PM, Pekka Enberg wrote:
And how many probes do we expected to be live at the same time in
real-world scenarios? I guess Avi's one million is more than enough?
Avi Kivity kirjoitti:
I don't think a user will ever come close to a
On Mon, 2010-01-18 at 14:37 +0200, Avi Kivity wrote:
On 01/18/2010 02:14 PM, Peter Zijlstra wrote:
Well, the alternatives are very unappealing. Emulation and
single-stepping are going to be very slow compared to a couple of jumps.
With CPL2 or RPL on user segments the protection
On 01/18/2010 03:15 PM, Peter Zijlstra wrote:
On Mon, 2010-01-18 at 14:37 +0200, Avi Kivity wrote:
On 01/18/2010 02:14 PM, Peter Zijlstra wrote:
Well, the alternatives are very unappealing. Emulation and
single-stepping are going to be very slow compared to a couple of
On Mon, 2010-01-18 at 14:53 +0200, Avi Kivity wrote:
On 01/18/2010 02:51 PM, Pekka Enberg wrote:
And how many probes do we expected to be live at the same time in
real-world scenarios? I guess Avi's one million is more than enough?
I don't think a user will ever come close to a
On Mon, Jan 18, 2010 at 02:15:51PM +0100, Peter Zijlstra wrote:
On Mon, 2010-01-18 at 14:37 +0200, Avi Kivity wrote:
On 01/18/2010 02:14 PM, Peter Zijlstra wrote:
Well, the alternatives are very unappealing. Emulation and
single-stepping are going to be very slow compared to a couple
On Mon, Jan 18, 2010 at 02:13:25PM +0200, Pekka Enberg wrote:
Hi Avi,
On Mon, 2010-01-18 at 14:01 +0200, Avi Kivity wrote:
Maybe you place no value on uprobes. But people who debug userspace
likely will see a reason.
On 01/18/2010 02:06 PM, Peter Zijlstra wrote:
I do see value in
Jim Keniston wrote:
Not really. For #3 (boosting), you need to know everything for #2,
plus be able to compute the length of each instruction -- which we can
now do for x86. To emulate an instruction (#4), you need to replicate
what it does, side-effects and all. The x86 instruction
On 01/18/2010 05:43 PM, Ananth N Mavinakayanahalli wrote:
Well, the alternatives are very unappealing. Emulation and single-stepping
are going to be very slow compared to a couple of jumps.
So how big chunks of the address space are we talking here for uprobes?
As Srikar
On Mon, Jan 18, 2010 at 06:52:32PM +0200, Avi Kivity wrote:
On 01/18/2010 05:43 PM, Ananth N Mavinakayanahalli wrote:
Well, the alternatives are very unappealing. Emulation and single-stepping
are going to be very slow compared to a couple of jumps.
So how big chunks of the address
On Mon, 2010-01-18 at 10:58 -0500, Masami Hiramatsu wrote:
Jim Keniston wrote:
Not really. For #3 (boosting), you need to know everything for #2,
plus be able to compute the length of each instruction -- which we can
now do for x86. To emulate an instruction (#4), you need to
On Mon, 2010-01-18 at 14:34 +0100, Mark Wielaard wrote:
On Mon, 2010-01-18 at 14:53 +0200, Avi Kivity wrote:
On 01/18/2010 02:51 PM, Pekka Enberg wrote:
And how many probes do we expected to be live at the same time in
real-world scenarios? I guess Avi's one million is more than
Jim Keniston wrote:
On Mon, 2010-01-18 at 10:58 -0500, Masami Hiramatsu wrote:
Jim Keniston wrote:
Not really. For #3 (boosting), you need to know everything for #2,
plus be able to compute the length of each instruction -- which we can
now do for x86. To emulate an instruction (#4),
We don't have any particular plans to extend the ptrace interface.
I strongly doubt we would even try to do anything like that until the
utrace-based ptrace interface is merged into Linux and the old ptrace
implementation gone.
In general, we are not looking for extensions to the ptrace
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