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Re: [PATCH v2 2.6.38-rc8-tip 6/20] 6: x86: analyze instruction and determine fixups.
- From: Roland McGrath <roland at hack dot frob dot com>
- To: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- Cc: Thomas Gleixner <tglx at linutronix dot de>, Peter Zijlstra <peterz at infradead dot org>, Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Linux-mm <linux-mm at kvack dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Andi Kleen <andi at firstfloor dot org>, Christoph Hellwig <hch at infradead dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Oleg Nesterov <oleg at redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, SystemTap <systemtap at sources dot redhat dot com>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, LKML <linux-kernel at vger dot kernel dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Fri, 18 Mar 2011 11:36:29 -0700 (PDT)
- Subject: Re: [PATCH v2 2.6.38-rc8-tip 6/20] 6: x86: analyze instruction and determine fixups.
- References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6> <20110314133507.27435.71382.sendpatchset@localhost6.localdomain6> <alpine.LFD.2.00.1103151529130.2787@localhost6.localdomain6> <20110318182457.GA24048@linux.vnet.ibm.com>
> handle_riprel_insn() returns 0 if the instruction is not rip-relative
> returns 1 if its rip-relative but can use XOL slots.
> returns -1 if its rip-relative but cannot use XOL.
>
> We dont see any instructions that are rip-relative and cannot use XOL.
> so the check and return are redundant and I will remove that in the next
> patch.
How is that? You can only adjust a rip-relative instruction correctly if
the instruction copy is within 2GB of the original target address, which
cannot be presumed to always be the case in user address space layout
(unlike the kernel).
Thanks,
Roland