From: Segher Boessenkool <segher@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>,
linuxppc-dev@ozlabs.org, mikey@neuling.org
Subject: Re: [RFC 5/8] powerpc/slb: Add documentation to runtime patching of SLB encoding
Date: Wed, 22 Jul 2015 07:17:15 -0500 [thread overview]
Message-ID: <20150722121715.GC11682@gate.crashing.org> (raw)
In-Reply-To: <1437544263.16792.12.camel@ellerman.id.au>
On Wed, Jul 22, 2015 at 03:51:03PM +1000, Michael Ellerman wrote:
> How about:
>
> /*
> * This function patches either an li or a cmpldi instruction with
> * a new immediate value. This relies on the fact that both li
> * (which is actually ori) and cmpldi both take a 16-bit immediate
> * value, and it is situated in the same location in the instruction,
> * ie. bits 0-15.
> * To patch the value we read the existing instruction, clear the
> * immediate value, and or in our new value, then write the instruction
> * back.
> */
As Gabriel says, li is addi. It takes a 16-bit sign-extended immediate,
while cmpldi takes a 16-bit zero-extended immediate. This function
doesn't deal with that difference, it probably should (I didn't check if
the callers take care; there should be an assertion somewhere).
Segher
next prev parent reply other threads:[~2015-07-22 12:17 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-21 6:58 [RFC 1/8] powerpc/slb: Remove a duplicate extern variable Anshuman Khandual
2015-07-21 6:58 ` [RFC 2/8] powerpc/slb: Rename all the 'entry' occurrences to 'slot' Anshuman Khandual
2015-07-21 9:46 ` [RFC, " Michael Ellerman
2015-07-21 11:23 ` [RFC,2/8] " Anshuman Khandual
2015-07-21 6:58 ` [RFC 3/8] powerpc/slb: Define macros for the bolted slots Anshuman Khandual
2015-07-22 9:32 ` Michael Ellerman
2015-07-21 6:58 ` [RFC 4/8] powerpc/slb: Add some helper functions to improve modularization Anshuman Khandual
2015-07-22 9:19 ` Michael Ellerman
2015-07-21 6:58 ` [RFC 5/8] powerpc/slb: Add documentation to runtime patching of SLB encoding Anshuman Khandual
2015-07-22 5:51 ` Michael Ellerman
2015-07-22 5:57 ` Gabriel Paubert
2015-07-22 9:01 ` Michael Ellerman
2015-07-22 12:17 ` Segher Boessenkool [this message]
2015-07-21 6:58 ` [RFC 6/8] powerpc/prom: Simplify the logic while fetching SLB size Anshuman Khandual
2015-07-21 10:21 ` [RFC, " Michael Ellerman
2015-07-21 11:24 ` Anshuman Khandual
2015-07-21 6:58 ` [RFC 7/8] powerpc/xmon: Drop 'valid' from the condition inside 'dump_segments' Anshuman Khandual
2015-07-21 10:00 ` [RFC, " Michael Ellerman
2015-07-21 11:45 ` Anshuman Khandual
2015-07-22 4:52 ` Michael Ellerman
2015-07-21 6:58 ` [RFC 8/8] powerpc/xmon: Add some more elements to the existing PACA dump list Anshuman Khandual
2015-07-21 10:08 ` [RFC, " Michael Ellerman
2015-07-21 11:48 ` Anshuman Khandual
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