Messages in this thread | | | Date | Fri, 6 Mar 2009 19:18:57 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH -tip 4/4] Atomic text_poke() with fixmap |
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* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> * Masami Hiramatsu (mhiramat@redhat.com) wrote: > > Use fixmaps instead of vmap/vunmap in text_poke() for avoiding page allocation > > and delayed unmapping. > > > > At the result of above change, text_poke() becomes atomic and can be called > > from stop_machine() etc. > > > > Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com> > > Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > > Cc: Ingo Molnar <mingo@elte.hu> > > --- > > arch/x86/include/asm/fixmap.h | 2 ++ > > arch/x86/kernel/alternative.c | 24 +++++++++++++++--------- > > 2 files changed, 17 insertions(+), 9 deletions(-) > > > > Index: linux-2.6-tip/arch/x86/kernel/alternative.c > > =================================================================== > > --- linux-2.6-tip.orig/arch/x86/kernel/alternative.c > > +++ linux-2.6-tip/arch/x86/kernel/alternative.c > > @@ -13,7 +13,9 @@ > > #include <asm/nmi.h> > > #include <asm/vsyscall.h> > > #include <asm/cacheflush.h> > > +#include <asm/tlbflush.h> > > #include <asm/io.h> > > +#include <asm/fixmap.h> > > > > #define MAX_PATCH_LEN (255-1) > > > > @@ -505,15 +507,16 @@ void *text_poke_early(void *addr, const > > * It means the size must be writable atomically and the address must be aligned > > * in a way that permits an atomic write. It also makes sure we fit on a single > > * page. > > + * > > + * Note: Must be called under text_mutex. > > */ > > void *__kprobes text_poke(void *addr, const void *opcode, size_t len) > > { > > + unsigned long flags; > > char *vaddr; > > - int nr_pages = 2; > > struct page *pages[2]; > > int i; > > > > - might_sleep(); > > if (!core_kernel_text((unsigned long)addr)) { > > pages[0] = vmalloc_to_page(addr); > > pages[1] = vmalloc_to_page(addr + PAGE_SIZE); > > @@ -523,14 +526,17 @@ void *__kprobes text_poke(void *addr, co > > pages[1] = virt_to_page(addr + PAGE_SIZE); > > } > > BUG_ON(!pages[0]); > > - if (!pages[1]) > > - nr_pages = 1; > > - vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL); > > - BUG_ON(!vaddr); > > - local_irq_disable(); > > + set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0])); > > Can the set_fixmap/clear_fixmap/local_flush_tlb be called > within local_irq_save ? If yes, that would be better, > especially for the SMP alternatives code, which would rely on > interrupt disabling in text_poke for consistency (the mutex is > not needed there).
yes, it is atomic.
Ingo
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