| Message ID | CAA3XUr0-KqtBw0WCFvws8g5ChK49d+X+7Un9ngq1UZg-oROx+A@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 04/11, Victor Kamensky wrote: > > On 10 April 2014 21:36, David Miller <davem@davemloft.net> wrote: > > You really need to pass the proper VMA down to the call site > > rather than pass NULL, that's extremely ugly and totally > > unnecesary. > > Agreed that VMA is really needed. I do not ;) but I am still trying to finish my email... > index 04709b6..1ae4563 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -117,6 +117,7 @@ struct xol_area { > * the vma go away, and we must handle that reasonably gracefully. > */ > unsigned long vaddr; /* Page(s) of instruction slots */ > + struct vm_area_struct *vma; /* VMA that holds above address */ > }; > > /* > @@ -1150,6 +1151,7 @@ static int xol_add_vma(struct mm_struct *mm, > struct xol_area *area) > > ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE, > VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page); > + area->vma = find_vma(mm, area->vaddr); No, this can't work. This vma can be unmapped/freed/etc. Oleg.
On 11 April 2014 07:26, Victor Kamensky <victor.kamensky@linaro.org> wrote: > On 10 April 2014 21:36, David Miller <davem@davemloft.net> wrote: >> From: David Long <dave.long@linaro.org> >> Date: Thu, 10 Apr 2014 23:45:31 -0400 >> >>> Replace memcpy and dcache flush in generic uprobes with a call to >>> copy_to_user_page(), which will do a proper flushing of kernel and >>> user cache. Also modify the inmplementation of copy_to_user_page >>> to assume a NULL vma pointer means the user icache corresponding >>> to this right is stale and needs to be flushed. Note that this patch >>> does not fix copy_to_user page for the sh, alpha, sparc, or mips >>> architectures (which do not currently support uprobes). >>> >>> Signed-off-by: David A. Long <dave.long@linaro.org> >> >> You really need to pass the proper VMA down to the call site >> rather than pass NULL, that's extremely ugly and totally >> unnecesary. > > Agreed that VMA is really needed. > > Here is variant that I tried while waiting for Oleg's response: > > From 4a6a9043e0910041dd8842835a528cbdc39fad34 Mon Sep 17 00:00:00 2001 > From: Victor Kamensky <victor.kamensky@linaro.org> > Date: Thu, 10 Apr 2014 17:06:39 -0700 > Subject: [PATCH] uprobes: use copy_to_user_page function to copy instr to xol > area > > Use copy_to_user_page function to copy instruction into xol area. > copy_to_user_page function guarantee that all caches are correctly > flushed during such write (including icache as well if needed). > > Because copy_to_user_page needs vm_area_struct, vma > field was added into struct xol_area. It holds cached vma value > for xol_area. > > Also using copy_to_user_page we make sure that we use the same > code that ptrace write code uses. > > Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org> > --- > kernel/events/uprobes.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 04709b6..1ae4563 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -117,6 +117,7 @@ struct xol_area { > * the vma go away, and we must handle that reasonably gracefully. > */ > unsigned long vaddr; /* Page(s) of instruction slots */ > + struct vm_area_struct *vma; /* VMA that holds above address */ > }; > > /* > @@ -1150,6 +1151,7 @@ static int xol_add_vma(struct mm_struct *mm, > struct xol_area *area) > > ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE, > VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page); > + area->vma = find_vma(mm, area->vaddr); > if (ret) > goto fail; > > @@ -1287,6 +1289,7 @@ static unsigned long xol_get_insn_slot(struct > uprobe *uprobe) > { > struct xol_area *area; > unsigned long xol_vaddr; > + void *xol_page_kaddr; > > area = get_xol_area(); > if (!area) > @@ -1297,8 +1300,11 @@ static unsigned long xol_get_insn_slot(struct > uprobe *uprobe) > return 0; > > /* Initialize the slot */ > - copy_to_page(area->page, xol_vaddr, > - &uprobe->arch.ixol, sizeof(uprobe->arch.ixol)); > + xol_page_kaddr = kmap_atomic(area->page); > + copy_to_user_page(area->vma, area->page, xol_vaddr, > + xol_page_kaddr + (xol_vaddr & ~PAGE_MASK), > + &uprobe->arch.ixol, sizeof(uprobe->arch.ixol)); > + kunmap_atomic(xol_page_kaddr); > /* > * We probably need flush_icache_user_range() but it needs vma. > * This should work on supported architectures too. Above comment and following call to 'flush_dcache_page(area->page);' should be removed of course. Just noticed that ... Thanks, Victor > -- > 1.8.1.4 > > Now while waiting for Oleg's response I am trying to run some performance > tests between different solution to understand situation better. > > One of my concerns was ARM smp function call that > could be reached from copy_to_user_page. But I have hard time > finding CPU that really doing it ... It does not look such call > will happen on relatively modern ARM CPUs (tried Arndale, > and Pandaboard ES). So my issues with use > of copy_to_user_page are quite elevated. > > Thanks, > Victor
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 04709b6..1ae4563 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -117,6 +117,7 @@ struct xol_area { * the vma go away, and we must handle that reasonably gracefully. */ unsigned long vaddr; /* Page(s) of instruction slots */ + struct vm_area_struct *vma; /* VMA that holds above address */ }; /* @@ -1150,6 +1151,7 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE, VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page); + area->vma = find_vma(mm, area->vaddr); if (ret) goto fail;