On Wednesday 20 August 2008 07:08, Steven Rostedt wrote: > On Tue, 19 Aug 2008, Mathieu Desnoyers wrote: > > Ok, there are two cases where it's ok : > > > > 1 - in stop_machine, considering we are not touching code executed in > > NMI handlers. > > 2 - when using my replace_instruction_safe() which uses a temporary > > breakpoint when doing the instruction replacement. > > > > In those cases you could use text_poke_early(). > > > > See > > http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=b > >lob;f=arch/x86/kernel/immediate.c;h=7789e2c75bf03e645f15759d5dff0c1698493f > >92;hb=HEAD > > > > For a use example. Basically it looks like : > > > > > > 360 pages[0] = virt_to_page((void *)bypass_eip); > > 361 vaddr = vmap(pages, 1, VM_MAP, PAGE_KERNEL); > > 362 BUG_ON(!vaddr); > > 363 text_poke_early(&vaddr[bypass_eip & ~PAGE_MASK], > > 364 (void *)addr, size); > > 365 /* > > 366 * Fill the rest with nops. > > 367 */ > > 368 len = NR_NOPS - size; > > 369 add_nops((void *) > > 370 &vaddr[(bypass_eip & ~PAGE_MASK) + size], > > 371 len); > > 372 print_dbg_bytes("inserted nops", > > 373 &vaddr[(bypass_eip & ~PAGE_MASK) + size], > > len); 374 vunmap(vaddr); > > vunmap can not be called with interrupts disabled, and this is exactly > what my code does.
It could be after the vmap rewrite (with a few other small tweaks). But a) it would be less robust when called from interrupt context and this code looks broken as it is WRT error handling; and b) it still costs several thousand cycles to vmap+touch+vunmap... _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
