Messages in this thread Patch in this message | | | Date | Tue, 3 Mar 2009 05:54:06 +0100 | From | Nick Piggin <> | Subject | Re: [RFC][PATCH] x86: make text_poke() atomic |
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On Mon, Mar 02, 2009 at 12:01:29PM -0500, Masami Hiramatsu wrote: > --- > > Use map_vm_area() instead of vmap() in text_poke() for avoiding page > allocation > and delayed unmapping, and call vunmap_page_range() and local_flush_tlb() > directly because this mapping is temporary and local. > > 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> > Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> > Cc: Nick Piggin <npiggin@suse.de> > --- > arch/x86/include/asm/alternative.h | 1 + > arch/x86/kernel/alternative.c | 36 > +++++++++++++++++++++++++++++------- > include/linux/vmalloc.h | 1 + > init/main.c | 3 +++ > mm/vmalloc.c | 2 +- > 5 files changed, 35 insertions(+), 8 deletions(-) > > Index: linux-2.6/arch/x86/include/asm/alternative.h > =================================================================== > --- linux-2.6.orig/arch/x86/include/asm/alternative.h > +++ linux-2.6/arch/x86/include/asm/alternative.h > @@ -177,6 +177,7 @@ extern void add_nops(void *insns, unsign > * The _early version expects the memory to already be RW. > */ > > +extern void text_poke_init(void); > extern void *text_poke(void *addr, const void *opcode, size_t len); > extern void *text_poke_early(void *addr, const void *opcode, size_t len); > > Index: linux-2.6/arch/x86/kernel/alternative.c > =================================================================== > --- linux-2.6.orig/arch/x86/kernel/alternative.c > +++ linux-2.6/arch/x86/kernel/alternative.c > @@ -12,6 +12,7 @@ > #include <asm/nmi.h> > #include <asm/vsyscall.h> > #include <asm/cacheflush.h> > +#include <asm/tlbflush.h> > #include <asm/io.h> > > #define MAX_PATCH_LEN (255-1) > @@ -485,6 +486,16 @@ void *text_poke_early(void *addr, const > return addr; > } > > +static struct vm_struct *text_poke_area[2]; > +static DEFINE_SPINLOCK(text_poke_lock); > + > +void __init text_poke_init(void) > +{ > + text_poke_area[0] = get_vm_area(PAGE_SIZE, VM_ALLOC); > + text_poke_area[1] = get_vm_area(2 * PAGE_SIZE, VM_ALLOC); > + BUG_ON(!text_poke_area[0] || !text_poke_area[1]); > +} > + > /** > * text_poke - Update instructions on a live kernel > * @addr: address to modify > @@ -501,8 +512,9 @@ void *__kprobes text_poke(void *addr, co > unsigned long flags; > char *vaddr; > int nr_pages = 2; > - struct page *pages[2]; > - int i; > + struct page *pages[2], **pgp = pages; > + int i, ret; > + struct vm_struct *vma; > > if (!core_kernel_text((unsigned long)addr)) { > pages[0] = vmalloc_to_page(addr);
This is really good....
> @@ -515,12 +527,22 @@ void *__kprobes text_poke(void *addr, co > BUG_ON(!pages[0]); > if (!pages[1]) > nr_pages = 1; > - vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL); > - BUG_ON(!vaddr); ^^^^^^^^^^^^^^ This really is nasty bug in text_poke, and I never knew why it was allowed to live for so long!
Thanks, Nick
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