| Date | Mon, 13 Jun 2011 14:29:55 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH v4 3.0-rc2-tip 2/22] 2: uprobes: Breakground page replacement. |
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* Peter Zijlstra <peterz@infradead.org> [2011-06-10 01:03:29]:
> On Tue, 2011-06-07 at 18:28 +0530, Srikar Dronamraju wrote: > > + vaddr_old = kmap_atomic(old_page, KM_USER0); > > + vaddr_new = kmap_atomic(new_page, KM_USER1); > > + > > + memcpy(vaddr_new, vaddr_old, PAGE_SIZE); > > + /* poke the new insn in, ASSUMES we don't cross page boundary */ > > + addr = vaddr; > > + vaddr &= ~PAGE_MASK; > > + memcpy(vaddr_new + vaddr, &opcode, uprobe_opcode_sz); > > + > > + kunmap_atomic(vaddr_new); > > + kunmap_atomic(vaddr_old); > > > > + vaddr_new = kmap_atomic(page, KM_USER0); > > + vaddr &= ~PAGE_MASK; > > + memcpy(opcode, vaddr_new + vaddr, uprobe_opcode_sz); > > + kunmap_atomic(vaddr_new); > >
> > Both sequences in resp {write,read}_opcode() assume the opcode doesn't > cross page boundaries but don't in fact have any assertions validating > this assumption. >
read_opcode and write_opcode reads/writes just one breakpoint instruction I had the below note just above the write_opcode definition.
/* * NOTE: * Expect the breakpoint instruction to be the smallest size instruction for * the architecture. If an arch has variable length instruction and the * breakpoint instruction is not of the smallest length instruction * supported by that architecture then we need to modify read_opcode / * write_opcode accordingly. This would never be a problem for archs that * have fixed length instructions. */
Do we have archs which have a breakpoint instruction which isnt of the smallest instruction size for that arch. If we do have can we change the write_opcode/read_opcode while we support that architecture?
-- Thanks and Regards Srikar > >
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