Messages in this thread | | | Date | Tue, 19 May 2015 01:35:31 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH 09/19] x86, mpx: trace entry to bounds exception paths |
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On Mon, 18 May 2015, Dave Hansen wrote:
> On 05/18/2015 01:58 PM, Thomas Gleixner wrote: > > On Fri, 8 May 2015, Dave Hansen wrote: > >> > This patch adds a trace point for the case where we are > >> > passing the exception up to userspace with a signal. > >> > > >> > We are also explicit that we're printing out the inverse of > >> > the 'upper' that we encounter. If you want to filter, for > >> > instance, you need to ~ the value first. > > Confused. What is the point of printing the complement of upper? > > If a pointer's range is > > 0x1000 -> 0x2000 > > it is stored in the bounds table as (32-bits here for brevity): > > lower: 0x00001000 > upper: 0xffffdfff > > That is so that an all 0's entry: > > lower: 0x00000000 > upper: 0x00000000 > > corresponds to the "init" bounds which store a *range* of: > > 0x00000000 -> 0xffffffff > > The 'upper' stored in the table is gibberish to print by itself, so we > print ~upper to get the *actual*, logical value.
Some comment in the code and the changelog might be helpful then :)
Thanks,
tglx
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