On Mon, Sep 06, 2021 at 12:39:56PM -0700, Greg Steuck wrote:
> In the course of making ASan work on OpenBSD I ran into an accounting
> limitation. struct vmspace declares vm_dsize as segsz_t (aka int32_t).
> This effectively limits it to 2^31 pages (2^43 bytes on amd64). This
> would be enough if didn't also count sparse allocation.
>
> ASan allocates 1/8th of the process address space as shadow memory. It
> is very sparsely populated, still given VM_MAXUSER_ADDRESS value of
> 0x00007f7fffffc000, it goes up to 2^47 bytes which then requires 2^44
> bytes of shadow. So, it won't fit.
>
> Hence the following unfinished patch which allows simple ASan'd programs
> to detect memory errors. If people don't see an alternative solution,
> I'll fix up the users of kinfo_proc.p_vm_dsize and we can decide
> when/how this should land.
>
> From 42c776531620e9baa6735da71349c3c045fb64d8 Mon Sep 17 00:00:00 2001
> From: Greg Steuck <g...@nest.cx>
> Date: Sun, 5 Sep 2021 13:28:43 -0700
> Subject: [PATCH] Change struct vmspace to use vsize_t vm_dused
>
> This was overflowing given high MAXDSIZ. This is very appropriate given
> that the field is usually incremented by a value returned by
> uvmspace_dused which returns vsize_t.
>
> The change is not finished, only kernel is fixed so far. Userspace
> tools consuming p_vm_dsize from kinfo_proc are likely not correct.
> ---
> sys/sys/sysctl.h | 2 +-
> sys/uvm/uvm_extern.h | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/sys/sys/sysctl.h b/sys/sys/sysctl.h
> index afdc0689dee..868ef82c696 100644
> --- a/sys/sys/sysctl.h
> +++ b/sys/sys/sysctl.h
> @@ -443,7 +443,7 @@ struct kinfo_proc {
>
> int32_t p_vm_rssize; /* SEGSZ_T: current resident set size
> in pages */
> int32_t p_vm_tsize; /* SEGSZ_T: text size (pages) */
> - int32_t p_vm_dsize; /* SEGSZ_T: data size (pages) */
> + u_int64_t p_vm_dsize; /* VSIZE_T: data size (pages) */
> int32_t p_vm_ssize; /* SEGSZ_T: stack size (pages) */
>
> int64_t p_uvalid; /* CHAR: following p_u* members from
> struct user are valid */
>From my understanding this is not how struct kinfo_proc should be modified.
Instead the code should add the u_int64_t version at the end and leave the
old in place. This way old userland still works with new kernel.
> diff --git a/sys/uvm/uvm_extern.h b/sys/uvm/uvm_extern.h
> index faa4a2e5449..ebc74d97917 100644
> --- a/sys/uvm/uvm_extern.h
> +++ b/sys/uvm/uvm_extern.h
> @@ -207,7 +207,7 @@ struct vmspace {
> segsz_t vm_swrss; /* resident set size before last swap */
> segsz_t vm_tsize; /* text size (pages) XXX */
> segsz_t vm_dsize; /* data size (pages) XXX */
> - segsz_t vm_dused; /* data segment length (pages) XXX */
> + vsize_t vm_dused; /* data segment length (pages) XXX */
> segsz_t vm_ssize; /* [v] stack size (pages) */
> caddr_t vm_taddr; /* [I] user virtual address of text */
> caddr_t vm_daddr; /* [I] user virtual address of data */
> --
> 2.33.0
>
--
:wq Claudio
