Messages in this thread | | | Date | Fri, 6 Mar 2009 13:45:06 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH -tip 4/4] Atomic text_poke() with fixmap take2 |
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* Masami Hiramatsu (mhiramat@redhat.com) wrote: > Mathieu Desnoyers wrote: > >> @@ -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, that just changes pte. > > --- > 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.
Maybe you could add "or in specific cases ensuring UP behavior".
The rest looks fine.
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> */ > 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(); > + local_irq_save(flags); > + set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0])); > + if (pages[1]) > + set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1])); > + vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0); > memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len); > - local_irq_enable(); > - vunmap(vaddr); > + clear_fixmap(FIX_TEXT_POKE0); > + if (pages[1]) > + clear_fixmap(FIX_TEXT_POKE1); > + local_flush_tlb(); > + local_irq_restore(flags); > sync_core(); > /* Could also do a CLFLUSH here to speed up CPU recovery; but > that causes hangs on some VIA CPUs. */ > Index: linux-2.6-tip/arch/x86/include/asm/fixmap.h > =================================================================== > --- linux-2.6-tip.orig/arch/x86/include/asm/fixmap.h > +++ linux-2.6-tip/arch/x86/include/asm/fixmap.h > @@ -111,6 +111,8 @@ enum fixed_addresses { > #ifdef CONFIG_PARAVIRT > FIX_PARAVIRT_BOOTMAP, > #endif > + FIX_TEXT_POKE0, /* reserve 2 pages for text_poke() */ > + FIX_TEXT_POKE1, > __end_of_permanent_fixed_addresses, > #ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT > FIX_OHCI1394_BASE, > -- > Masami Hiramatsu > > Software Engineer > Hitachi Computer Products (America) Inc. > Software Solutions Division > > e-mail: mhiramat@redhat.com >
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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