• Dave Hansen's avatar
    x86/mpx: Trace entry to bounds exception paths · 97efebf1
    Dave Hansen authored
    There are two basic things that can happen as the result of
    a bounds exception (#BR):
    
    	1. We allocate a new bounds table
    	2. We pass up a bounds exception to userspace.
    
    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.  The reason we do
    this is because of how 'upper' is stored in the bounds table.
    
    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
    
    That is, by far, the common case, and that lets us use the
    zero page, or deduplicate the memory, etc... The 'upper'
    stored in the table is gibberish to print by itself, so we
    print ~upper to get the *actual*, logical, human-readable
    value printed out.
    Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
    Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Dave Hansen <dave@sr71.net>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: http://lkml.kernel.org/r/20150607183703.027BB9B0@viggo.jf.intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    97efebf1
mpx.h 1.99 KB