On Tue, 2015-07-21 at 12:28 +0530, Anshuman Khandual wrote: > From: "khand...@linux.vnet.ibm.com" <khand...@linux.vnet.ibm.com> > > This patch adds some documentation to 'patch_slb_encoding' function > explaining about how it clears the existing immediate value in the > given instruction and inserts a new one there. > > diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c > index dcba4c2..8083a9e 100644 > --- a/arch/powerpc/mm/slb.c > +++ b/arch/powerpc/mm/slb.c > @@ -278,7 +278,13 @@ void switch_slb(struct task_struct *tsk, struct > mm_struct *mm) > static inline void patch_slb_encoding(unsigned int *insn_addr, > unsigned int immed) > { > - int insn = (*insn_addr & 0xffff0000) | immed; > + /* > + * Currently this patches only "li" and "cmpldi" > + * instructions with an immediate value. Here it > + * just clears the existing immediate value from > + * the instruction and inserts a new one there. > + */ > + unsigned int insn = (*insn_addr & 0xffff0000) | immed; > patch_instruction(insn_addr, insn); > }
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. */ cheers _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev